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Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes (2023)

Chapter: Chapter 7: Revegetation and Pollinators: Design and Implementation

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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
×
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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Suggested Citation:"Chapter 7: Revegetation and Pollinators: Design and Implementation." National Academies of Sciences, Engineering, and Medicine. 2023. Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes. Washington, DC: The National Academies Press. doi: 10.17226/27071.
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7-1 Chapter 7 Revegetation and Pollinators: Design and Implementation 7.1 Introduction  Habitat loss is a leading factor in the decline of many pollinators (NRC 2007), and increasing pollinator habitat is an effective conservation strategy (e.g., Tonietto and Larkin 2018). Revegetation on roadsides involves replanting and reestablishing plant communities in areas where the vegetation and habitat have been disturbed or removed. In addition to providing a safe driving environment, common roadside revegetation objectives include erosion control, water quality protection, weed control, visual enhancement, carbon sequestration, and wildlife enhancement. Enhancing habitat for pollinators can be addressed while meeting these other objectives. Improving roadside habitat for imperiled pollinator species through revegetation can help to preclude the need to list new species under the U.S. Endangered Species Act (ESA) and can help to support listed and common pollinator species alike. Roadside revegetation projects that incorporate habitat needs of pollinators can result in habitat that can be used by a species for its whole life cycle (e.g., a ground-nesting bee nests in roadside soil and forages on roadside vegetation), or support a species for a portion of its life cycle (e.g., host plants support the caterpillar stage of a butterfly’s life). Roadsides with intact native plant communities can lessen the effects of habitat fragmentation by functioning as corridors and connecting larger habitat patches (Forman et al. 2003; Huijser and Clevenger 2006; Dániel-Ferreira et al. 2022a). Additionally, if roadside revegetation projects contain plenty of floral resources, pollinators will be less likely to seek habitat elsewhere, reducing the risk of being killed by vehicles (Ries et al. 2001; Skórka et al. 2013). The removal of noxious and invasive plant species increases pollinator abundance and diversity (Hanula and Horn 2011; Fiedler et al. 2012), and roadside revegetation projects that replace invasive plants with native vegetation improve pollinator habitat. It can be a challenge to recreate the exact habitat needs of some imperiled species; augmenting existing habitat through management or restoration is preferable whenever possible. If construction alters roadside habitat of a listed species, compliance commonly occurs using processes under Section 7 and Section 10 of the ESA. Permanent removal of habitat or delays in reestablishing habitat can result in population declines and losses of species from the site that may not be regained. Native plants on roadsides like this sundial lupine (Lupinus perennis) showcase regional beauty while also providing pollinators with habitat. Photo Credit: Chris Staron, Ohio DOT

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-2 7.2 Considering Imperiled Pollinators in Revegetation  Enhancing habitat for imperiled pollinators, or for pollinators in general, can be a specific objective for revegetation projects. Even if it is not a specific objective, elements that increase the value of the revegetation project to pollinators can be incorporated into other project objectives. To meet objectives such as water quality protection and erosion control, quick-growing native wildflowers and grasses can be used, including species that also provide resources for pollinators. Deep-rooted shrubs or trees might be used for visual enhancement, stabilization, snow retention, or carbon sequestration; selecting species that provide larval food or pollen and nectar will also enhance the project’s value to pollinators. Consideration of the needs of pollinators when planning a revegetation project can have significant benefits for pollinators. Pollinators have complex life cycles, with different needs at different stages of their lives. Table 7-1 provides an overview of habitat needs of pollinators and how revegetation projects can meet those needs. Chapter 3 of this guide includes profiles of listed and imperiled pollinators within this region, with natural history information, such as specific habitat needs. Table 7-1. Roadside revegetation goals for enhancing habitat for different groups of pollinators. Pollinators  Food for Larval  Stage  Food for  Adult  Shelter,  Overwintering  General  Revegetation Goals  Bumble bees  Provisions of  nectar and  pollen within  the nest.  Nectar.  Nest in small  underground  cavities in  abandoned  rodent nests,  under clumps of  grass, or in  hollow trees, bird  nests, or walls.   Increase density and diversity of native flowering plants.  Include species with sequential bloom periods; early season blooms are particularly important.  Plant native bunch grasses for bumble bee nesting habitat. Ground‐ nesting bees  Provisions of  nectar and  pollen within  the nest.  Nectar.  Excavate nest  tunnels in bare or  partially  vegetated, well‐ drained soil.   Increase density and diversity of native flowering plants.  Retain areas with bare or partially vegetated, well‐ drained soil.

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-3 Pollinators  Food for Larval  Stage  Food for  Adult  Shelter,  Overwintering  General  Revegetation Goals  Tunnel‐ nesting bees  Provisions of  nectar and  pollen within  the nest.  Nectar.  Nest in narrow  tunnels in dead  standing trees, or  excavate nests in  hollow stems or  pith of twigs.  Some construct  domed nests of  mud, plant  resins, saps, or  gums on the  surface of rocks  or trees.   Increase density  and diversity of  native flowering  plants.   Retain or install  woody plants and  herbaceous plants  with hollow or  pithy stems.    Leave snags of  non‐hazard trees  outside of the  recovery zone.  Beetles  Some species  are herbivorous,  feeding on  plants; many are  carnivorous and  eat prey such as  aphids, slugs,  and insect eggs.  Pollen,  nectar, floral  parts; some  species are  also  carnivorous.  Overwinter in soil  or leaf litter,  under rocks, logs,  brush, or bark.   Increase density  and diversity of  native flowering  plants.   Retain  overwintering  sites when  feasible.  Butterflies  Vegetation of  host plants.  Nectar; some  males obtain  nutrients,  minerals, and  salt from  rotting fruit,  tree sap,  animal dung  and urine,  carrion, clay  deposits, and  mud puddles.  Protected site  such as a tree,  bush, tall grass,  or a pile of  leaves, sticks, or  rocks.   Increase density  and diversity of  native flowering  plants.   Include specific  host plants.   Maintain  vegetation  structure.  Flower‐ visiting  moths  Vegetation of  host plants.  Nectar.  Protected site  such as a tree,  bush, tall grass,  or a pile of  leaves, sticks, or  rocks.   Increase density  and diversity of  native flowering  plants.   Include specific  host plants.   Maintain  vegetation  structure. 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-4 Pollinators  Food for Larval  Stage  Food for  Adult  Shelter,  Overwintering  General  Revegetation Goals  Flies  Some species  are carnivorous,  consuming prey  such as aphids,  scales, or mites;  others are  decomposers in  the soil.  Nectar; some  species also  eat pollen.  Overwinter in soil  or leaf litter.   Increase density  and diversity of  native flowering  plants.   Retain  overwintering  sites when  feasible.  Wasps  Provisions of  insect prey such  as caterpillars,  aphids,  grasshoppers,  planthoppers,  true bugs, and  more.  Nectar.  Many nest in the  ground; others  nest in tunnel  nests in wood or  cavities in mud or  resin.   Increase density  and diversity of  native flowering  plants.   Retain areas with  partially vegetated  well‐drained soil.   Retain or install  woody plants and  herbaceous plants  with hollow or  pithy stems.  Roadsides can provide pollinators with their key habitat needs—food for larvae and adults, and shelter and overwintering habitat. In particular, native plants are important for pollinators. Roadsides with native wildflowers support a greater number of individuals and species of butterflies and bees compared with those dominated by non-native grass and flowers (Ries et al. 2001; Hopwood 2008). Native plants are more attractive as sources of pollen and nectar for pollinators than non-native plants and support more species and more individuals seeking pollen or nectar, even when both plant types are present on the same site (Williams et al. 2011; Morandin and Kremen 2013). Native plants also support more caterpillars than do non-native plants (Narango et al. 2017); native woody plants used as ornamentals in the eastern U.S. support fifteen times more native butterflies and moths than do introduced species of ornamental plants (Tallamy and Shropshire 2009). Adding non-native plants to landscapes does not increase butterfly and moth diversity or abundance (Burghardt et al. 2010), and non-native plants can reduce bird populations as a consequence of reduced insect availability (Narango et al. 2018). 7.2.1 Use of Native Plants in Revegetation Establishing native plant communities on roadsides provides economic benefits as well as ecological advantages (Berger 2005). Native plants can support safety objectives by reducing headlight glare, serving as crash barriers, reducing wind speed across roads, and reducing snow drifts across roads (Forman et al. 2003). Additionally, wildflowers and other flowering plants on the roadside improve driver performance by breaking up driver

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-5 monotony, contributing to clearer thinking, and reducing driver stress (Topp 1990; Cackowsky and Nasar 2003; Mok et al. 2006; Macdonald et al. 2008). Native grasses and flowers are best adapted to local growing conditions, require minimal inputs for establishment, and are able to tolerate drought or heat, which will become more common in many regions.  Some native species are particularly able to tolerate the poor growing conditions found on roadsides (Harper-Lore and Wilson 2000; O’Dell et al. 2007).  Under some conditions, native plants have a competitive advantage over non-natives (Tinsley et al. 2006).  An established diverse native plant community provides the most stable cover for reducing erosion and keeping out weeds (Quales 2003; Blumenthal et al. 2005; Falk et al. 2013).  Improved weed and erosion control can reduce the need to spray herbicides and to mow, thereby reducing long-term maintenance costs (Berger 2005; O’Dell et al. 2007; Harper-Lore et al. 2013).  The root systems of native plants can increase water infiltration, which reduces runoff and water pollution and helps to replenish groundwater (Cramer 1991; Bugg et al. 1997; Harrison 2014). Native plants are less likely to encroach on land bordering roadsides and rarely become weed issues (Harper-Lore and Wilson 2000). In contrast, a number of introduced species used for roadside revegetation have become weed problems elsewhere, including crown vetch (Securigera varia), sweet clover (Melilotus spp.), sericea lespedeza (Lespedeza cuneata), reed canary grass (Phalaris arundinacea), and smooth brome (Bromus inermis) (Harper-Lore and Wilson 2000). Finally, native revegetation plantings are aesthetically pleasing and can support tourism. The Texas Department of Transportation (DOT) has several designated wildflower routes, for example, that showcase native wildflowers; when bluebonnets (six species of Lupinus that are collectively considered the state flower of Texas) are in bloom, some towns along these routes hold bluebonnet festivals. Travelers form perceptions about regions based on their views of the highway landscape, and drivers prefer “natural-looking roadsides with native grasses, wildflowers, and butterflies,” to turf roadsides (Guyton et al. 2014). Roadsides with native plants can showcase a region’s natural beauty and provide a sense of place, natural heritage, and opportunities for education. Natural beauty may also align with driver preferences. One study conducted in Minnesota on driver perception of Native plants are species that  originated in or occur naturally in a  particular geographic area. Grasses,  wildflowers, shrubs, and trees that  existed before European settlement  of North America are native plants.  Native plants are best suited to local  conditions, generally require less  maintenance, and persist longer that  non‐local species. They can form plant  communities that are robust, self‐ sustaining, and resilient.   Native plants are central to healthy,  functional ecosystems. They support  soil health and water quality,  sequester carbon, and are habitat for  wildlife. Native plants are at the heart  of food webs, as they are food  sources for animals such as  caterpillars or grasshoppers that in  turn feed birds, frogs, and other  animals. Native plants also support  more pollinators and more wildlife  than do non‐native plants (Narango et  al. 2017; Williams et al. 2011).  Native plant root systems can be extensive and support resilience to drought, fires, and weeds. Photo Credit: Heidi Natura, Conservation Research Institute

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-6 roadside landscapes found that prairie plantings were ranked as most attractive, and a mix of trees, shrubs, and prairie also ranked highly. Mown turf, along with brome grass with a mowed turf edge, were ranked the least attractive by drivers (Nassauer et al. 2006). Similarly, a majority of Iowa drivers preferred the appearance of managed roadside prairie plantings (Nemec et al. 2021). In a Georgia study of rest area plantings, the traveling public found block plantings of a single species most attractive but preferred overall a matrix of species due to the environmental benefits. Additionally, 87 percent of those surveyed preferred native plants over non-native for roadside plantings (Tania et al. 2020). Native Plants and Safety Concerns During roadside revegetation design, a roadside planting and maintenance plan can be used to contribute to the reduction of animal browsing within the right-of-way (ROW). If designated or safe crossing points (e.g., crossing structures) exist, native vegetation can be used to provide conditions that will attract wildlife to those points. In areas that have high wildlife–vehicle collision rates, it is important to focus on planting species that have low palatability close to the roadway (Huijser et al. 2008). Arizona DOT’s approach has been to exclude plant species from its seed mixes that “green up” early or are otherwise known to attract deer and other large wildlife species. It has worked with partners on some projects to plant palatable species in areas leading to designated bridged wildlife crossings or habitat adjacent to roadside ROWs (Brown et al. 1999). In areas with known high wildlife–vehicle collision rates, prioritizing shorter plant material (3 feet tall or less; this should not include flowers or seed head stalks) will provide less cover for large mammals and will allow drivers to potentially see and respond to animals in the ROW. When palatability is known, it is included in the plant lists in this chapter (Table 7-3). It is also important to consider the frequency and timing of cutting and mowing maintenance. Maintaining a regularly mown recovery zone can increase driver visibility and reduce deer–vehicle collisions (Mastro et al. 2008). However, cutting and mowing can attract browsing activity because large hoofed mammals (such as white-tailed deer or moose) prefer to browse on fresh growth. Consideration of nutritional value of key forage plants for large mammals as it relates to cutting is important in areas with high rates of wildlife–vehicle collisions (e.g., Rea 2003). Reduced mowing beyond the safety zone may decrease deer foraging because mowing can increase the palatability of some plants (Mastro et al. 2008). 7.3 Design Considerations for  Revegetation Projects  7.3.1 Roadside Plants as Food for Pollinators Flowering plants in roadsides are important sources of nectar and pollen for pollinators that reside within the roadside habitat (e.g., Blooming bluebonnets are colorful sight on Texas roadsides between March and May. Photo Credit: Texas DOT A green sweat bee collecting pollen. Photo Credit: Barbara Driscoll

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-7 Munguira and Thomas 1992), as well as those that use the roadside as a partial habitat for foraging but reproduce or overwinter elsewhere (e.g., Ouin et al. 2004). The availability of pollen and nectar influences the abundance and diversity of pollinators found on roadsides (Saarinen et al. 2005; Hopwood 2008). Different pollinators have different floral needs and preferences, so including a diversity of plant species with different flower shapes, sizes, colors, and growth habits helps support a variety of pollinators (Ghazoul 2006; Ponisio et al. 2015). It is important to have flowers available to pollinators throughout the growing season. While pulses of bloom can provide critical resources to pollinators, sustained resources without temporal gaps create functional habitat throughout the growing season to best support robust populations and communities. Bees that emerge early in the growing season can begin to forage in April in the Great Lakes region, with late-season bees foraging through October. Within that period, different species will be active at different times. Solitary bees have distinct flight seasons that last 4 to 6 weeks. Bumble bees are social, with an annual colony that expands gradually and requires forage throughout the growing season. Similarly, different species of butterflies and moths may have distinct emergence periods with one generation a year, or multiple generations a year. For an example of a phenology chart that illustrates overlapping bloom periods, see Table 7-2. Table 7-2. Bloom calendar for several wildflower species found in the Great Lakes region. Plant Species  March  April  May  June  July  Aug  Sept   Oct   Amelanchier laevis                  Salix humilis                  Geranium maculatum                  Penstemon gracilis                  Rosa blanda                  Penstemon hirsutus                  Lobelia siphilitica                  Euthamia graminifolia                  Symphyotrichum novae‐ angliae                 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-8 It can be helpful to emulate the species diversity found on reference sites in nearby natural plant communities. Diverse plantings that resemble natural communities are the most self- sustaining and longest lasting because they better resist weed invasions and pest outbreaks. When possible, prioritize the use of plant materials that are sourced from local ecotype providers. Plant materials that originated in geographic proximity to the project site are best adapted for local growing conditions and for pollinators. The bloom times of non-locally sourced plants have the potential to be out of sync with pollinators (Norcini et al. 2001), especially specialist bees that are reliant on the pollen from a small subset of plants and time their emergence annually with the bloom time of their host plants, or butterflies seeking to lay eggs on their host plants before the plants senesce. However, there is an emerging school of thought about the potential importance of including genetic diversity in plantings to increase the likelihood of adaptations to changes in the climate. Using multiple local sources within the region may be one way to address this concern. See Chapter 8 for discussion of strategies to address climate change through seed provenance. 7.3.2 Roadside Plants as Shelter for Pollinators Woody vegetation such as trees and shrubs can provide shelter for pollinators during the growing season, and can also provide niches for overwintering. Some pollinators will overwinter under bark or in the soil just under shallow roots, or in piles of brush. Grasses can provide shelter for a variety of pollinators, but notably for butterflies on roadsides (Saarinen et al. 2005). The root systems and grass thatch can also serve as overwintering habitat for a variety of pollinators. Nesting is a critical factor affecting the ability of bees to persist within a site (Winfree 2010; Menz et al. 2011; Morandin and Kremen 2013). Ground-nesting bees need access to soil surfaces between vegetation to excavate and access their nests (Michener 2007). Some species will nest in a variety of soils, while others have very specific requirements for the soil type, moisture, alkalinity, slope, and aspect (Cane 1991). Bunch grasses tend to provide better nesting habitat than sod-forming grasses. Roadsides with native bunch grasses have more nesting opportunities for ground-nesting bees and, consequently, a greater abundance of ground-nesting bees (Hopwood 2008). A number of aboveground nesting bees nest in hollow stems or excavate pithy stems (e.g., elderberry or cane fruits), while other native bees nest in tunnels in wood, such as abandoned beetle tunnels in logs, stumps, and snags (Michener 2007). Plant lists included in this chapter provide information about known plants that provide nesting resources for bees. Maintaining dead wood, snags, or wood with holes in it (e.g., fence posts) where safe and appropriate within the project site will also benefit tunnel-nesting bees. Bumble bee colonies require an insulated cavity in which to nest, such as underneath grass clumps (Svennson et al. 2000), under the thatch of bunch grasses, or under rocks (Hatfield et al. 2012). Some bee species create nests in plant stems. Roadside plants can provide shelter and nesting resources for bees and other pollinators. Photo Credit: Sara Morris

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-9 7.3.3 Roadsides and Connectivity Landscape connectivity is increasingly important for the populations of many species, including pollinators (Haddad 1999; Haddad and Baum 1999). Roadsides have the potential to help pollinators move between habitat fragments by acting as corridors or stepping stones to connect to larger patches of habitat (Soderstrom and Hedblom 2007; Dániel-Ferreira et al. 2022). Pollinators may use roadsides as corridors to facilitate movement through the landscape in search of food or in pursuit of new habitat (Lövei et al. 1998; Ries et al. 2001; Valtonen and Saarinen 2005; Hopwood et al. 2010), or they may expand their ranges along roadsides (Dirig and Cryan 1991; Brunzel et al. 2004). Corridors like roadsides and other linear strips of vegetation such as utility ROWs may provide habitat resilience as changes in climate drive species range contractions or expansions. 7.3.4 Designs and Conservation Practices There are a number of conservation practices to consider when designing revegetation plans. The following revegetation design practices benefit pollinators broadly:  Prioritize native plants in designs. Roadsides with native plants support more species of pollinators and larger populations (Ries et al. 2001; Hopwood 2008). Native flowering trees, shrubs, and wildflowers provide nectar and pollen or are host plants. Native grasses are also host plants and provide shelter.  Prioritize sourcing native plants locally. Plant materials that are sourced locally or within the ecoregion are best for pollinators because the phenology (flowering period) can also differ with the provenance of the plant material (Norcini et al. 2001; Houseal and Smith 2000; Gustafson et al. 2005). Bloom times of non-locally sourced plants have the potential to be out of sync with pollinators. This may be particularly problematic for bee species that are pollen specialists (e.g., the thistle longhorn bee [Melissodes desponsa] is a pollen specialist on thistles) because they are reliant on the pollen from a small subset of plants and time their emergence from overwintering with the bloom time of their host plants. Locally sourced ecotypes are also adapted to local conditions.  Increase flowering plant diversity and abundance. High flowering plant diversity provides sustained resources throughout the growing season to best support robust pollinator populations and communities. Higher plant diversity can also reduce pollinator exposure to heavy metals and salts, as different plant species uptake pollutants at different rates. Floral abundance is also important. Sparse resources will not sustain pollinator populations, whereas high densities of blooms are more attractive and can support higher numbers of pollinators (Herrera 1989). A diverse combination of grasses and wildflowers can also effectively resist weed colonization and provide soil stabilization. Having 45 percent cover of flowering Highway overpasses with habitat plantings and structures—such as the I-90 Snoqualmie Pass East Restoration Project that connects habitat on either side of I-90—benefit large wildlife as well as small wildlife like pollinators. Photo Credit: Kelly Evans / Washington DOT A roadside in Arkansas with a variety of  flowering plants. Incorporating diversity into  revegetation projects has many benefits,  including supporting a larger number of  pollinators and increased climate resilience.  Photo Credit: Ray Moranz, The Xerces Society 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-10 plant vegetation across a growing season in seed mixes should be the goal in order to prevent grasses from outcompeting wildflowers. Flowering plant cover could be spread out throughout the growing season, with 15 percent cover of species that flower in spring, 15 percent in summer, and 15 percent in autumn.  Include species with overlapping and sequential bloom periods. Providing a diversity of flowering plants throughout the growing season supports species with multiple generations as well as those that time their emergence and flight period with the bloom of certain plant species. This approach also provides a more resilient plant community that can better support a diversity of pollinators. Early-season pollen and nectar sources are important for those species that have flight seasons in the late winter or spring, as well as those with season-long flights, and will lead to greater reproduction of those species. Increasing the diversity of flowering plants in seed mixes and planting plans can help to prevent gaps in bloom. Revegetation design practices for imperiled pollinator species include:  Include key host plants for target pollinator species. Imperiled butterflies and moths may rely on plants of a single species or genus as host plants for their caterpillars. Providing caterpillar host plants is a well-established way to sustain butterfly and moth populations (Croxton et al. 2005; Feber et al. 1996). Roadsides with host plants can support habitat generalist butterflies as well as habitat specialists and migrant species, such as the monarch butterfly (e.g., Ries et al. 2001). Many native plants commonly used in revegetation projects serve as butterfly and moth host plants (e.g., little bluestem [Schizachyrium scoparium]). However, it is necessary to include specific native host plant species matched to support the particular butterfly or moth species that are adapted to feeding on them. For example, planting milkweeds (Asclepias spp.) will contribute to the recovery of the monarch butterfly. Plant lists included in this guide include specific host plants for butterflies and moths that are imperiled (Table 7-3).  Consider the bloom time of flowering plants within the project area. Include a number of different species of flowering plants during the flight time of focal pollinators. Adults of butterflies and moths of most imperiled and listed species have limited flight times; therefore, make sure that in addition to host plants, a site has plenty of flowering plants during the flight time of the adults (see Chapter 3 or 6 for flight times of adults).  Include key nectar and/or pollen plants for target pollinator species. Some pollinator species have dietary restrictions and need the floral resources from certain flowering plants to survive. For example, bees that are pollen specialists can only rear their young on pollen from a certain species or groups of closely related plants. Bumble bee species have different tongue lengths that allow them to preferentially feed on certain flowers. Adult butterflies are often generalist foragers of nectar, but some species may exhibit preferences for nectar from certain plants. For example, grass skippers in the Midwest and Great Plains prefer to drink nectar from purple coneflowers (Echinacea spp.) and blazing stars (Liatris spp.) (Moranz 2010; Dana 1991). Plant lists included in this guide include known nectar plants for imperiled and listed species (Table 7-3). Many butterflies use specific plant species as  host plants for their caterpillars. Including  hostplants of butterflies that occur in the area  will contribute to pollinator conservation.  Photo Credit: Anne Stine, The Xerces Society 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-11  Consider additional specific habitat needs, such as nesting or overwintering habitat. Some imperiled species have very specific habitat needs. For instance, a bumble bee species may prefer nesting aboveground in a particular type of insulated cavity, and a tunnel-nesting yellow-faced bee needs a particular place to tunnel. Consult the profiles of listed and imperiled pollinators in Chapter 3 to learn more about any specific habitat needs. In general, including a diversity of types of plants in revegetation plans can help to ensure that vegetation structure that can act as shelter and overwintering habitat is present. Trees and shrubs may not be appropriate for every revegetation project; in those situations, including a diversity of grasses (both cool and warm season grasses) can increase vegetation structure.  Consider the connectivity of planned revegetation sites to existing habitat within the landscape. Developing a landscape connectivity map of the project area and adjacent lands—using information collected during the vegetation assessment that locates areas of high, medium, and low pollinator habitat qualities—can be a base for designing a revegetation plan that improves pollinator habitat within the context of larger landscape connectivity. Corridors with high-quality habitat support more butterfly species, including specialist species, and population persistence (Habel et al. 2020; Dániel-Ferreira et al. 2022a). It is also important to prioritize those projects that can increase the connectivity of existing roadside habitat. If remnant roadside habitat exists, for example, it would be very beneficial if revegetation projects with high plant diversity were installed adjacent to or nearby.  Consider timing of revegetation projects. While high quality revegetation is ultimately beneficial to pollinators, it can lead to a temporary decrease in the availability of food and nesting resources for pollinators. If a revegetation project is being conducted in an area with an imperiled pollinator, ideally the project should be timed to avoid adult flight times or other sensitive times in the species’ life cycle (Chapter 3). 7.3.5 Developing a Plant Species List To improve pollinator habitat as a revegetation objective, select a mix of plant species and site improvements that encourage foraging, breeding, nesting, and overwintering of a variety of pollinator species. Revegetation efforts for pollinators should use diverse, stable communities of plants that include key plant species that support local pollinators, including imperiled and state- or federally listed pollinator species. Plant diversity in a revegetation plan is important from several angles. Diverse plant communities are better able to prevent erosion and resist weed invasions, and they are more persistent over time and more resilient as climates shift (see Chapter 8 for more information). Roadsides are variable in soil type and moisture, fertility, land-use history, solar radiation, and more. With such a range of microsites, diverse plantings help ensure that there are a number of species that could fill in the various niches; if one or more species does not do well at the site, there are others that will, creating a resilient system. Diverse plantings also best support pollinators, providing flowers that have sequential bloom periods, host plants for breeding, nest sites, grasses that provide vegetative structure for shelter and overwintering, and more. Different plant groups provide different functional roles and benefits, and they can occupy different niches. Cool-season rhizomatous grasses green up early in the spring and can provide erosion control from late winter into early summer, while warm-season grasses

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-12 provide erosion control as they grow through the summer months and into the fall. Legumes can fix nitrogen and improve soil health. Annual or biennial wildflowers can establish quickly and provide attractive vegetative cover, erosion control, and food for pollinators and birds while slower-growing, but deeper-rooted, perennial species establish. Shrubs and trees also play important roles in revegetation projects, where appropriate, and are ecologically valuable to pollinators as well. Guidelines for developing a species list that supports pollinators and other revegetation objectives are presented below:  Select species adapted for the sunlight and soil conditions present at the roadside site (e.g., use moisture-tolerant species for wet ditches). Projects that contain special microclimates or soils may require a unique mix of species. If seed mixes cannot be context-specific, include species adapted to a wide range of growing conditions.  Prioritize the use of native plants. Avoid using introduced (non-native) species in high- quality mixes, as these species may outcompete native plants during establishment, diminishing the quality of habitat over time and supporting fewer species of pollinators.  Include key plant species that support imperiled pollinators, such as host plants for caterpillars or plants that are known to provide nectar or pollen to adults.  Ensure that non-aggressive species are able to establish by limiting the abundance of aggressive species as needed.  Avoid temporal gaps in bloom periods. To ensure that there are always flowers in bloom, include multiple species that bloom in the spring, species that bloom in summer, and those that bloom in the fall. Some mixes fall short on spring blooms in particular (Havens and Vitt 2016).  Design plantings with plant communities in mind, and include species that will grow well together.  Include layers of plants. For example, include an understory of shrubs, wildflowers, grasses, or sedges with tree plantings. Layers help to shade out weeds, reduce moisture loss, provide layers of habitat for wildlife, and reduce maintenance requirements.  If installing vegetation via seeding, balance the proportion of grass seeds to wildflower seeds. If grass density is too high, grasses will outcompete wildflowers over time, reducing plant diversity. At minimum, 25 percent of the seed mix should be wildflowers, but a mix that is 50 percent wildflowers results in a considerably more diverse and stable planting (Dickson and Busby 2009). In highly visible areas, consider increasing the wildflower component to create more showy plantings, if that is an objective for the revegetation site.  Check erosion control mulches or straw, seed laboratory reports, and legal seed labels of the planting stock. Mulches, seed, and other planting stock should be free of noxious weeds, invasive or introduced species, and other crop components. This planting, made as part of a bridge  replacement and interchange reconfiguration,  includes layers of native trees like oaks and  hawthorn; shrubs such as viburnum,  chokeberry, and bayberry; and perennial  grasses.   Photo Credit: Tara Mitchell, Massachusetts DOT 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-13  Where available and economical, native plants and seed should be procured from local ecotype providers. Local ecotype plant materials are adapted to the local climatic conditions, will generally establish well, and will have bloom times in sync with the presence of monarchs and other pollinators. Some cultivars have been bred for a particular trait such as showiness and may have little to no pollen and nectar and therefore little value to pollinators.  Avoid taller herbaceous plants in areas where lines of sight could be blocked, such as intersections and other safety zones.  In areas with snow and ice, species to be planted close to the road should have some level of salt tolerance to reduce damage from road salt applications.  When possible, salvage native plants, particularly those that are more difficult to establish or are longer lived, from the site prior to construction and disturbance for use in the revegetation project. Enlist the help of other agencies or volunteers to temporarily relocate the salvaged vegetation for installation at the site after construction or for installation at another appropriate site. 7.3.6 Plants for Imperiled Pollinators in the Great Lakes Region This plant list includes wildflowers and flowering shrubs and trees that are sources for pollen and/or nectar for a diversity of pollinators, plants that serve as host plants for caterpillars of butterflies and moths, and grasses, sedges, and woody species that provide nesting or materials for nesting for bees and wasps.  All species in this list are native to this region. Many have been commercially available (White et al. 2018). Contact local or regional native plant producers to check on their current availability or to inquire about species that may require collecting plant materials for propagation.  Many of the species in this list are “workhorse” species that broadly support pollinators, are found in a number of ecological settings in abundance, and are relatively easy to propagate. Workhorse species also tend to survive well once they are installed.  This list also includes plant species that are important for imperiled pollinators listed in Chapter 3. Some of these plant species do not meet the workhorse criteria, and may be more challenging to establish. They may also be less widely available commercially or more expensive because they take more time to propagate.  This plant list is available as an Excel file on the National Academies Press website (https://nap.nationalacademies.org). These saguaro cacti, which are very slow  growing and long‐lived plants, are relocated  temporarily during a construction project.  Photo Credit: Arizona DOT 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-14 Table 7-3. Native Plants with value to pollinators for use on roadsides in the Great Lakes region. Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Agastache  scrophulariifolia  Purple giant  hyssop  Jul–Sep  Perennial  Shrub,  forb  Sun, part  shade,  shade  Dry      X      Agrostis spp.  Bentgrass  Mar–Aug  Perennial  Grass  Sun, part  shade,  shade  Wet,  moist, dry  X          Andropogon gerardii  Big bluestem  Jun–Sep  Perennial  Grass  Sun, part  shade  Wet,  moist, dry  X      X  X  Amelanchier laevis  Allegheny  serviceberry  Mar–Apr  Perennial  Tree,  shrub  Sun, part  shade,  shade  Moist, dry            Asclepias incarnata  Swamp  milkweed  Jun–Sep  Perennial  Forb  Sun, part  shade  Moist  X  X  X  Stems    Asclepias  purpurascens  Purple  milkweed  May–Jul  Perennial  Forb  Sun  Moist, dry  X  X  X  Stems  X  Asclepias sullivantii  Prairie  milkweed  Jun–Aug  Perennial  Forb  Sun  Moist  X  X  X    X  Asclepias syriaca  Common  milkweed  Jun–Aug  Perennial  Forb  Sun, part  shade  Moist, dry  X  X  X  Stems    Asclepias tuberosa  Butterfly  milkweed  Jun–Aug  Perennial  Forb  Sun, part  shade  Dry  X  X  X  Stems    Asclepias viridiflora  Green comet  milkweed  Jun–Sep  Perennial  Forb  Sun  Dry  X  X  X  Stems   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-15 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Baptisia spp.  Wild indigo  May–Aug  Perennial  Forb  Sun, part  shade  Moist, dry  X    X  Stems  X  Bouteloua  curtipendula  Sideoats grama    Perennial  Grass  Sun, part  shade  Dry  X      X    Bouteloua gracilis  Blue grama    Perennial  Grass  Sun  Dry  X      X  X  Bouteloua hirsuta  Hairy grama            X          Carex bebbii  Bebb’s sedge  May–Jun  Perennial  Sedge  Sun, part  shade,  shade  Wet            Carex bromoides  Brome‐like  sedge  Apr–Jun  Perennial  Sedge  Part shade,  shade  Wet,  moist  X          Carex scoparia  Broom sedge  May–Jun  Perennial  Sedge  Sun, part  shade,  shade  Wet,  moist            Carex stricta  Tussock sedge  Apr–May  Perennial  Sedge  Sun, part  shade,  shade  Wet  X          Carex vulpinoidea  Fox sedge  Apr–May  Perennial  Sedge  Sun, part  shade  Wet          X  Ceanothus  americanus  New Jersey tea  Jun–Jul  Perennial  Shrub  Sun, part  shade  Dry    X  X      Cirsium discolor  Field thistle  Aug–Oct  Biennial  or  perennial  Forb  Sun  Moist    X  X  Nests and  materials   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-16 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Coreopsis lanceolata  Lanceleaf  tickseed  Apr–Jun  Perennial  Forb  Sun  Moist, dry      X      Coreopsis palmata  Stiff tickseed  Jun–Aug  Perennial  Forb  Sun, part  shade  Moist, dry    X  X    X  Crataegus spp.  Hawthorn  Apr–May  Perennial  Tree,  shrub  Sun, part  shade  Wet,  moist, dry      X    X  Dalea purpurea  Purple prairie  clover  Jul–Aug  Perennial  Shrub,  forb  Sun  Dry    X  X    X  Dasiphora fruticosa  Shrubby  cinquefoil  May–Jul  Perennial  Shrub  Sun, part  shade  Wet,  moist  X    X      Desmodium  canadense  Showy  ticktrefoil  Jun–Sep  Perennial  Forb  Sun, part  shade  Moist, dry      X  Materials    Digitaria cagnota  Fall witchgrass  Jul–Sep  Perennial  Grass  Sun, part  shade  Dry  X        X  Echinacea  angustifolia  Narrowleaf  coneflower  May–Jul  Perennial  Forb  Sun, part  shade  Dry    X      X  Echinacea pallida  Pale purple  coneflower  May–Aug  Perennial  Forb  Sun  Moist, dry    X    Stems  X  Eleocharis elliptica  Elliptic  spikerush  May–Sep  Perennial  Sedge  Sun  Wet  X          Elymus canadensis  Canada wildrye  Jul–Aug  Perennial  Grass  Sun, part  shade  Moist, dry        Thatch  X  Eupatorium  perfoliatum  Common  boneset  Jun–Oct  Perennial  Forb  Sun, part  shade  Wet,  moist      X  Stems   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-17 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Euthamia graminifolia  Grass‐leaved  goldenrod  Jul–Sep  Perennial  Forb  Sun, part  shade  Wet,  moist      X      Eutrochium  maculatum  Spotted Joe Pye  weed  Jul–Sep  Perennial  Forb  Sun, part  shade  Wet      X  Stems    Gentiana andrewsii  Closed bottle  gentian  Aug–Oct  Perennial  Forb  Sun  Moist      X      Geranium maculatum  Spotted  geranium  Apr–May  Perennial  Forb  Sun, part  shade  Moist, dry    X  X      Helenium autumnale  Common  sneezeweed  Sep–Nov  Perennial  Forb  Sun, part  shade  Wet,  moist      X      Helianthus spp.  Sunflower  Jun–Sep  Annual or  perennial  Forb  Sun, part  shade  Wet,  moist, dry    X  X  Stems  X  Heliopsis  helianthoides  Smooth oxeye  Jun–Aug  Perennial  Forb  Sun  Moist, dry    X  X  Stems  X  Koeleria macrantha  Prairie  junegrass  May–Jun  Perennial  Grass  Sun, part  shade,  shade  Dry        Thatch  X  Liatris aspera  Rough blazing  star  Jul–Oct  Perennial  Forb  Sun, part  shade  Wet,  moist, dry    X  X  Stems    Liatris ligulistylis  Meadow  blazing star  Jul–Sep  Perennial  Forb  Sun  Moist    X  X  X  X  Liatris pycnostachya  Prairie blazing  star  Jul–Sep  Perennial  Forb  Sun  Wet,  moist, dry    X  X  X    Lobelia siphilitica  Great blue  lobelia  Jun–Aug  Perennial  Forb  Sun  Wet,  moist    X  X     

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-18 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Lobelia spicata  Palespike  lobelia  Jun–Aug  Perennial  Forb  Sun, part  shade  Wet,  moist    X  X    X  Lupinus perennis  Wild lupine  Apr–Jun  Perennial  Forb  Sun  Dry  X  X  X      Monarda fistulosa  Wild bergamot  May–Sep  Perennial  Shrub,  forb  Sun, part  shade  Moist, dry    X  X  Stems  X  Muhlenbergia  richardsonis  Mat muhly  Jun–Jul  Perennial  Grass  Sun, part  shade  Wet,  moist  X          Oligoneuron rigidum  Rigid goldenrod  Aug–Oct  Perennial  Forb  Sun, part  shade  Dry    X  X  X  X  Panicum virgatum  Switchgrass  Jul–Aug  Perennial  Grass  Sun, part  shade  Wet,  moist, dry        Thatch  X  Panicum wilcoxianum  Fall rosette  grass  May–Sep  Perennial  Grass  Sun  Dry  X          Penstemon gracilis  Slender beard  tongue  May–Jun  Perennial  Forb  Part shade  Moist, dry    X        Penstemon hirsutus  Hairy  beardtongue  Jun–Jul  Perennial  Forb  Sun, part  shade  Moist, dry    X  X      Physocarpus  opulifolius  Common  ninebark  Apr–Jun  Perennial  Shrub  Sun, part  shade  Moist      X      Prunus virginiana  Black  chokecherry  Apr–May  Perennial  Tree,  shrub  Sun, part  shade  Moist, dry      X    X  Pycnanthemum  virginianum  Virginia  mountainmint  Jun–Aug  Perennial  Forb  Sun  Moist    X  X  Stems   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-19 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Ratibida pinnata  Pinnate prairie  coneflower  Jun–Aug  Perennial  Forb  Sun  Moist, dry      X  Stems  X  Rosa blanda  Smooth wild  rose  May–Jun  Perennial  Shrub  Sun, part  shade  Moist, dry      X  Nests and  materials    Rubus spp.  Blackberries  Apr–Aug  Perennial  Shrub  Sun, part  shade,  shade  Wet,  moist, dry    X  X  X    Rudbeckia hirta  Black‐eyed  Susan  Jun–Sep  Biennial  Forb  Sun, part  shade  Moist, dry    X  X    X  Sagittaria latifolia  Broadleaf  arrowhead  May–Sep  Perennial  Forb  Sun, part  shade  Wet    X  X      Salix humilis  Prairie willow  Mar–May  Perennial  Shrub  Sun, part  shade  Moist, dry      X    X  Schizachyrium  scoparium  Little bluestem  Aug–Sep  Perennial  Grass  Sun, part  shade  Moist, dry  X      Thatch  X  Scirpus expansus  Woodland  bulrush  Jul–Aug  Perennial  Sedge  Part shade,  shade  Wet  X          Silphium laciniatum  Compass plant  Jul–Sep  Perennial  Forb  Sun  Moist, dry    X  X    X  Solidago nemoralis  Gray goldenrod  Jul–Oct  Perennial  Forb  Sun, part  shade  Dry    X  X    X  Solidago speciosa  Showy  goldenrod  Aug–Sep  Perennial  Forb  Sun, part  shade  Dry    X  X  Stems    Sorghastrum nutans  Indiangrass  Jul–Sep  Perennial  Graminoid  Sun  Moist, dry        Thatch  X 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-20 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Spiraea alba  White  meadowsweet  May–Jun  Perennial  Shrub  Sun, part  shade  Wet,  moist      X  Materials    Sporobolus  heterolepis  Prairie  dropseed  Jun–Sep  Perennial  Grass  Sun  Moist, dry  X X  X  Sporobolus neglectus  Puffsheath  dropseed  Aug–Oct  Perennial  Grass  Sun  Dry  X Symphyotrichum  lateriflorum  Calico aster  Aug–Oct  Perennial  Forb  Sun  Wet,  moist  X  X  Stems  Symphyotrichum  novae‐angliae  New England  aster  Aug–Oct  Perennial  Forb  Sun  Wet,  moist  X  X  X  Stems  Tilia americana  American  basswood  May–Jun  Perennial  Tree  Sun, part  shade  Moist, dry  X  X  Tradescantia ohiensis  Ohio  spiderwort*  Apr–Jun  Perennial  Forb  Sun, part  shade  Wet,  moist, dry  X  X  Vaccinium spp.  Blueberries  Apr–Sep  Perennial  Shrub  Sun, part  shade,  shade  Wet,  moist, dry  X  X Verbena stricta  Hoary verbena  Jun–Sep  Annual or  perennial  Forb  Sun  Dry  X  X  Veronicastrum  virginicum  Culver's root  Jun–Aug  Perennial  Forb  Sun  Wet,  moist, dry  X  X  Stems  Viburnum spp.  Viburnum  May–Jul  Perennial  Tree,  shrub  Sun, part  shade,  shade  Wet,  moist, dry  X  X  Stems 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-21 Scientific Name  Common Name  Bloom  Period  Life Cycle  Form  (Forb,  Shrub,  Tree,  Sedge,  Grass)  Sun  Soil (Dry,  Moist,  Wet)  Imperiled  Butterfly  and Moth  Larval  Host  Nectar/  Pollen for  Imperiled  Pollinators  Bumble  Bee  Plant  Nest Site  or Nest  Materials  Deer  Resistant  Viola pedata  Birdfoot violet  Apr–May  Perennial  Forb  Sun, part  shade  Dry  X  X  X      Viola pedatifida  Prairie violet  Apr–Jun  Perennial  Forb  Sun  Dry  X  X        Viola sororia  Violet  Apr–Jun  Perennial  Forb  Sun, part  shade  Wet,  moist, dry  X  X  X    X  Zizia aurea  Golden  alexanders  Apr–Aug  Perennial  Forb  Sun, part  shade  Wet,  moist, dry  X    X  Stems   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-22 To identify additional species appropriate to this region and valuable to pollinators, use the Ecoregional Revegetation Assistant Tool, a map-based online tool to aid practitioners when selecting native plants for restoration and pollinator habitat enhancement. The map can be used to find a state or US Environmental Protection Agency Level III Ecoregion, and the tool will produce a list of plants and plant attributes suitable for that area. The database includes plant attributes such as soil type, moisture needs, palatability, salt tolerance, value to pollinators, and workhorse plant species. Data can be downloaded by county, state, or ecoregion, and plant species can be filtered by attributes. The tool is available at http://www.nativerevegetation.org/era. When designing revegetation projects, it is important to consult with the site’s maintenance department. Maintenance departments have processes and practices in place for reasons that may not be known to habitat designers, and coordination with maintenance can improve revegetation outcomes. Discussions with maintenance departments can help to build willingness to adapt maintenance practices to facilitate pollinator habitat establishment and persistence. Consider if the agency could create a staff position that focuses on ecological roadside revegetation and is shared by both the maintenance and design teams. This role could ensure that what is designed gets implemented across the state and can be maintained effectively by maintenance crews. Box 7‐1. Rest areas, welcome centers, and pollinator habitat  Welcome centers and rest areas are places  where the traveling public can relax and take  a break. DOTs also provide learning  opportunities at these stopping points,  where signs and brochures are frequently  used to inform the public. DOTs can also use  these spaces to create demonstration  gardens or plantings, including pollinator  habitat. These plantings help DOTs inform  the public about pollinators and habitat that  support them, and showcase conservation  efforts.   Signage for this Ohio DOT planting describes  why pollinators are important and plants that  support them.   Photo Credit: Joel Thrash, Ohio DOT 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-23 Plantings for pollinators at rest areas or welcome centers can also be opportunities for  experimentation, places where DOTs can trial particular seed mixes or planting methods on a  smaller scale before implementing them on a larger area. Wisconsin DOT, for example, is  currently restoring prairie at two of its busiest rest areas, removing invasive species and  interseeding additional prairie species. There  are also opportunities for collaborations and  partnerships in these spaces. Georgia DOT is  in the process of installing pollinator habitats  at some of rest areas and welcome centers,  in partnership with the Georgia Association  of Conservation Districts. Kansas DOT worked  with partners to trial prescribed burning to  manage plantings at several of their rest  areas.    7.4 Installation Considerations for Revegetation   7.4.1 Sourcing Plant Materials Obtaining locally or regionally sourced native plant materials in sufficient quality and quantities for a project involves advance planning. Coordination with native plant providers early in the planning process is important. If a special plant species is needed for a site, the agency or plant vendors can collect wild plant material and amplify seeds, cuttings, or plants with enough lead time. Guidance for collecting and propagating wild-type plant materials can be found in Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat (FHWA 2017): http://www.nativerevegetation.org/learn/manual_2017/chpt5_implementation/5_3_obta in_plant_mat.aspx. If there are not enough abundance and diversity of locally sourced species available for a project, prioritize regionally sourced native plant materials. These might include species that do not naturally occur in the local ecosystem but are present within the region. If regional plant materials cannot be found, consult restoration experts and seed producers to determine if cultivars may be appropriate to use for the site. Commercial cultivars are less preferable because some do not provide sufficient pollen or nectar to support pollinators, and some may either not establish effectively in the area or may become too aggressive at the expense of other valuable plants. However, cultivars might be appropriate in some locations for certain revegetation objectives (e.g., landscape planting in an urban setting). When obtaining seed, it is recommended to require vendors to provide a seed testing certificate for each species in the seed mix. Commercially procured seed is certified to guarantee a number of quality standards, including proper species, germination rate, and Invasive brush and a dead tree are removed  from a prairie restoration at a Wisconsin rest  area before additional wildflower seeds are  added.   Photo Credit: Wisconsin DOT 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-24 any amount of weed seed or inert material. Review the certificate before purchase of the seed lot and reject seed lots that contain undesirable species as contaminants that might pose a risk to the planting. Native Plants and Costs of Revegetation Although the initial costs of establishing native plant material may be more significant than using widely available introduced species, particularly for projects that include a higher density and diversity of flowering plants or specialized species, native plants are often more cost effective in the long term. Once established, the native plants persist well over time and often require less mowing, herbicides, and other weed control measures, decreasing long-term maintenance efforts and cost (Berger 2005). For more information about costs and benefits of native plants, see Chapter 10. Legislation Supporting Native Plants on Roadsides Federal Legislation In 2014, the White House issued a Presidential Memorandum, “Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators.” This memo directed the U.S. Department of Transportation to evaluate guidance and identify opportunities to increase pollinator habitat along roadways, and to work with state DOTs and transportation associations to promote practices that support pollinators, including increasing native plantings. In 2015, the Fixing America’s Surface Transportation (FAST) Act was signed into law and included language on efforts to support pollinators. Section 1415 of the FAST Act authorizes that activities to establish and improve pollinator habitat may be eligible for federal funding if they are related to transportation projects funded under Title 23, U.S.C. Additionally, Section 1415 of the FAST Act directs the Federal Highway Administration (FHWA), in conjunction with willing states, to encourage: 1. Integrated vegetation management practices on roadsides and other transportation rights-of-way, including reduced mowing; and 2. The development of habitat and forage for Monarch butterflies, other native pollinators, and honey bees through plantings of native forbs and grasses, including noninvasive, native milkweed species that can serve as migratory way stations for butterflies and facilitate migrations of other pollinators. In 2021, the Infrastructure Investment and Jobs Act included language to establish two funding programs that could be used to support pollinator habitat for agencies that manage roadsides. Section 11522 established the Invasive Plant Elimination Program to provide grants to states to control invasive species, up to $50 million per year (for fiscal years 2022– 2026). Priority is given to projects that utilize revegetation with native plants that support pollinators. Section 11528 established the Pollinator-Friendly Practices on Roadsides and Highway Rights-of-Way grant program to provide grants of up to $150,000 for use in the development, implementation, or improvement of a pollinator-friendly practices plan, with up to $2 million available per year ((for fiscal years 2022–2026). Examples of pollinator- friendly practices include:  mowing strategies that limit disturbance during periods of highest use by target species;

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-25  an integrated vegetation management plan to address weed issues;  the planting of native species to enhance pollinator habitat;  removal of non-native species from species mixes; and  obtaining expert training or assistance on pollinators-friendly practices. Funding was not appropriated by Congress as part of the FY 2022 budget for either the Invasive Plant Elimination Program or the Pollinator-Friendly Practices grant program but will hopefully be included in future budgets. Beyond FHWA, many other land management agencies in the United States have policies mandating the prioritization of native plants in revegetation projects, including the U.S. Forest Service and the Bureau of Land Management. State Legislation At the state level, there have been several approaches to encouraging native plants as the first choice in revegetation efforts. In Iowa, the state legislature passed Integrated Roadside Vegetation Management (IRVM) legislation in 1987 to promote an ecologically integrated approach to roadside management, while maintaining a safe travel environment (Code of Iowa, Section 314, available here: https://www.legis.iowa.gov/docs/ico/code/314.pdf). The legislation emphasized the establishment and protection of native vegetation as well as judicious use of herbicides, mowing, prescribed burning, and other management tools. The bill also established the Living Roadway Trust Fund, an annual competitive grant program administered by the Iowa DOT that provides funding for school, city, county, and state projects, as well as research projects involving IRVM. Iowa’s road use tax, along with several other sources, funds the Living Roadway Trust Fund. County roadside managers can submit applications to obtain resources to help them implement IRVM, including vegetation inventories, native seeds, equipment for burns or plant establishment, GPS units, signage, workshops, and more. Roadsides are seeded with mixes of species that are appropriate for a particular site, including many wildflowers that are attractive to pollinators. Seed mixes also contain species that bloom at different times throughout the growing season, which helps support pollinators all season long. Research projects have also been supported by the Living Roadway Trust Fund, including studies of restoration techniques. Since the bill passed, more than 100,000 acres of Iowa’s nearly 600,000 acres of state and county roadsides have been planted with native vegetation (Brandt et al. 2011). In the process, Iowa has fostered the development of experienced roadside managers who are equipped to collaborate with other land managers around the state and bring habitat, and wildlife such as pollinators, back to Iowa’s much-altered landscape. In 2017, New Jersey passed a bill that requires New Jersey DOT, New Jersey Turnpike Authority, and the South Jersey Transportation Authority to use only native vegetation for landscaping, land management, reforestation, or habitat restoration. The legislation also directed the Department of Environmental Protection and Department of Agriculture to identify plants native to the state in hardiness zones within the state. Proponents of the bill pointed to saving taxpayers expenses due to replanting, and to benefits for wildlife and clean water. The text of the bill can be found here:

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-26 https://legiscan.com/NJ/text/S227/2016. North Carolina passed an act to prioritize the use of native plants on roadsides in 2019. Recognizing that native plants are part of North Carolina’s natural heritage and are well adapted to North Carolina’s landscapes, the bill directs North Carolina to give precedence to the use of native trees, shrubs, vines, grasses, and wildflowers in erosion control and landscaping projects, as well as in roadside parks, scenic overlooks, and picnic areas. The bill can be found here: https://webservices.ncleg.gov/ViewBillDocument/2019/2522/0/DRS35248-MW-38. 7.4.2 Prioritizing Sites for Revegetation Efforts to Benefit Imperiled Pollinators It can be helpful to prioritize sites for roadside revegetation projects that support imperiled pollinators in order to maximize conservation value and use resources effectively. Considerations to guide decisions about prioritization of sites to improve pollinator habitat include:  Presence of target pollinator species. Prioritize locations where a listed or imperiled pollinator species is known to be in the vicinity or was previously found at the site.  Landscape connectivity. Prioritize sites that improve connectivity of existing habitat within the landscape.  Landscape diversity. Prioritize sites that exist in an area important to the target pollinator species and is in a landscape in which habitat is scarce, and therefore roadside habitat would be particularly valuable to pollinators.  Roadside width. Prioritize wider sites because they appear to support greater numbers and diversity of pollinator species. Medians are lower priorities because they are often narrow and, due to their placement between roads, may pose a higher risk from vehicle mortality to pollinators.  Traffic density. Prioritize sites with lower roadway traffic density.  Road density. Prioritize sites that are not isolated within areas of high road density in which there are multiple barriers to pollinator movement (e.g., cloverleaf median off an interstate interchange in an urban area).  Visibility to the public. Consider prioritizing sites that are more visible to the public if public awareness and education is a goal. Use the scorecard in Box 7-2 to determine a site’s attributes and its relative suitability for prioritizing enhancement for pollinators.

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-27 Box 7‐2. Scorecard for prioritizing sites for revegetation to support imperiled pollinators  Resources  to  install  high  quality,  diverse  native  plant  material  may  be  limited.  Limited  resources can be leveraged by prioritizing some roadside sites for revegetation that involves  habitat restoration for imperiled or at‐risk pollinators. Use this tool to help determine a score  for a site that can be helpful in site prioritization. Select all the options that apply to the site:  ⌧  Presence of focal pollinator species. A listed or imperiled pollinator species is known to be  in the vicinity or was previously found at the site. (2pts)  ⌧  Landscape  connectivity.  The  site  improves  connectivity  of  existing  habitat within  the  landscape. For example, the site  is near or connected to a natural area (e.g., state park,  national  forest,  nature  preserve)  or  connects  with  existing  high  quality  roadside  vegetation. (2pts)  ⌧  Landscape diversity. The site exists in an area important to the focal pollinator species and  is  in  a  landscape  in  which  habitat  is  scarce;  therefore,  roadside  habitat  would  be  particularly valuable to pollinators. (2pts)  ⌧  Project scale. The planned project is large in scale; the size of a habitat patch influences  the number of individuals and species that use it. (1pt)  ⌧  Roadside  width.  Wider  sites  are  preferred  because  they  appear  to  support  greater  numbers and diversity of pollinator species. (1pt)  ⌧  Traffic density. Sites with higher traffic density (more than four lanes of traffic) on adjacent  roads may be less desirable for pollinators. (1pt)  ⌧  Road density. Site  is not  isolated within areas of high  road density  in which  there are  multiple  barriers  to  pollinator  movement  (e.g.,  cloverleaf  median  off  an  interstate  interchange in an urban area). (1pt)  ⌧  Visibility to the public. Sites that are more visible to the public may be important for DOT  goals, including public awareness and education. (1pt)  ⌧  Weed pressure: The site has low weed pressure from noxious and invasive weeds. (1pt)  ⌧ Benefits to adjacent land. The existing or future road network is in lands largely dominated  by agricultural activities that could benefit from pollinators. (1pt)  Final score: ______________   Scale:   Scores of 7 or more points: This site is a high priority for revegetation with pollinators in mind.  Scores of 4–6 points: This site is a medium priority for revegetation with pollinators in mind.  Scores of 3 and lower: This site is a lower priority for revegetation with pollinators in mind.   

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-28 Chapter 9 includes a tool to help evaluate sites for their conservation value to pollinators: the Pollinator Habitat Assessment Guide for Roadsides. The tool includes a rapid assessment and a comprehensive assessment of roadside pollinator habitat. The comprehensive assessment includes 1) a category to determine the priority of the roadside site within the context of the larger landscape and 2) a category that evaluates possible threats to pollinators from the adjacent road and surrounding land. The scores from those categories can help to guide choices about prioritizing projects that emphasize an objective to improve habitat for imperiled pollinators. The Roadside Pollinator Habitat Assessment Guide is available on the National Academies Press website (https://nationalacademies.org). 7.4.3 Plant Establishment After disturbance or construction, roadside sites may be in poor condition for plant growth. Mitigation measures may be needed, such as reconstructing soils (note: if new soils are brought to a location, they should be free of invasive seeds, to the extent possible) or making amendments through composts or fertilizers or the introduction of beneficial microorganisms that play crucial roles in soil and plant health. Topographic enhancements to improve the plant establishment can also be made. These include modifying topography to capture runoff water for use by plants or creating terraces on slopes to support seedling establishment. Installing Plant Materials Installing diverse native plant materials, including diverse seed mixes, requires consideration of timing of installation and matching installation method to the site characteristics. Generally, diverse seed mixes have the best establishment when planted in the fall or during the dormant season, allowing the many species that require cycles of cold moisture to germinate. Transplants generally do best when installed in winter or early spring when soil moisture is high, or sometimes in the fall for dormant plants. In this region, the optimal timing to install native plant materials is presented in Table 7-4. Table 7-4. Timing windows for installing native plants in the Great Lakes region. When to Seed  When to Install Container  Plants  When to Install Bare Roots  Dormant season  Early fall or spring  Mar–May  Although these time windows are optimal for plant establishment, it may be especially difficult to time seeding accordingly because of time constraints from construction schedules. Seeding should take place as needed for erosion control after repairs or construction, as long as the seed is protected in place (e.g., under a layer of hydrostraw tackifier or compost blanket) until the conditions for germination occur. The Monarch Joint Venture and  partners (funded through the  National Academy of Sciences  Transportation Research Board’s  National Cooperative Highway  Research Program) developed a  habitat prioritization model for  roadsides as monarch butterfly  habitat for DOTs. The model can  help managers assess potential  areas of habitat along roads in their  state or identify where habitat  could be developed. More  information about the model can be  found here:  https://nationalacademies.org/.  

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-29 When installing seeds, select the method of seeding that is most appropriate for the site. See Table 7-5 for an overview of the advantages, disadvantages, and tips on seeding techniques, using the three main seeding methods used in roadside revegetation. General guidance on installing native seeds to achieve optimal establishment includes:  Place seed in direct contact with soil, and do not bury the seed more than ¼ inch deep, which will affect establishment. If broadcasting seed, tamp or press down the seed lightly into the soil using a tractor or cultipacker after planting. If hydroseeding, apply the seed, mixed with fertilizer and a small amount of fiber or straw and tackifier first, then follow up with a second pass of hydromulch mixed with tackifier to hold it in place. This ensures seeds are covered by the hydromulch.  If the site requires rapid plant establishment, include nurse or cover crops in seed mixes to help hold the soil while native species establish. Suitable nurse crops include sterile hybrids or annuals such as oats (Avena sativa), winter wheat (Triticum aestivum), or rye (Lolium multiflorum).  Coordinate with maintenance staff about conducting weed control during the establishment phase. Weed control to reduce weed competition while allowing native seedlings to grow is critical in the first and second years after planting. Weeds should also be prevented from going to seed. Use spot-sprays of herbicides as needed or mowing where appropriate. (See “Short-Term Management: Before and During Establishment” below.)  Because roadsides planted with seed can take time to establish, it may be helpful to install a sign to indicate the site is a planting that is underway. Table 7-5. Seeding methods for planting seed and the techniques involved. Seeding  Method  Where to Use  Site  Preparation  Needed  Seeding  Techniques  Following  Seeding  Broadcast  seeders or  hand  broadcasting   (Throwing  seed)   This method is  inexpensive and  easy to use. It is  particularly  useful for sites  that cannot be  reached by  mechanical  equipment.   Spreading seed  evenly over site is  difficult, and the  seed bed must be  smooth.   Greater  quantities of  seed (up to 50%   Remove as  much  stubble as  possible  prior to  planting,  creating a  smooth  lightly  packed  seedbed.   Seed before  a rain.   Bulk up seed  using an  inert carrier,  such as sand  or clay‐based  cat litter.   Make  multiple  passes,  scattering  seed over  the site.   Pack the  seed into the  soil using a  tractor or  cultipacker. 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-30 Seeding  Method  Where to Use  Site  Preparation  Needed  Seeding  Techniques  Following  Seeding  more) are  required.   Additional step of  pressing seed  into soil after  seeding to help  germination is  required.  Drill seeding  (Using a  native seed  drill)   Drill seeding is  convenient for  planting large,  level areas, but it  does not work  well on slopes.   Seed can be  planted into  areas with light  stubble and seed  does not need to  be pressed into  the soil.   Depth at which  seeds are planted  can be  controlled.   An experienced  operator is  required.   Seed can be  planted into  stubble.   Plant when  the soil is dry  enough to  prevent  sticking to  the parts of  the drill.   Set depth  controls to  plant no  deeper than  1/4 inch.   Make  multiple  passes with  the drill to  pack the  seed in well.  Hydroseeding  (Spraying the  area with a  mix of water,  mulch, and  seed)   Hydroseeding is  useful for slopes,  culverts, bridge  approaches, and  wet areas  because it  reduces soil  erosion.   The project can  be seeded from  the shoulder.   Hydroseeding is  good for visible  sites; hydromulch  can hold the seed   Bare ground  is needed,  but the  seedbed  does not  need to be  smooth.   Seed after a  rain if  possible.   Apply the  seed first,  mixed with  fertilizer and  a small  amount of  fiber or  straw and  tackifier.  Then follow  up with a  second pass  of  hydromulch  mixed with  tackifier to  hold the   No action is  required  following  seeding. 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-31 Seeding  Method  Where to Use  Site  Preparation  Needed  Seeding  Techniques  Following  Seeding  in place until  there is enough  moisture for  germination and  protect it from  seed predators.   Hydromulch can  be expensive,  and the seeding  rate is harder to  control; well‐ trained  applicators are  needed.  seed in  place.   Seed the  area furthest  from the  road first.  General installation guidelines for optimizing establishment of transplants include the following:  Determine the equipment needed for the installation of transplants. Shovels are often adequate for excavating holes for many transplants, but power augers are a particularly efficient way to create a hole for large container stock. Steep or rocky slopes may require specialized planting equipment such as expandable stingers.  Stage the planting before digging holes. The objectives of the project will determine the planting patterns, whether transplants will be spaced out evenly, in clumps, or at random. Remember to consider the size of each species at maturity when spacing out plants. For example, most woody shrubs should be spaced on 4- to 10-foot centers to give them ample room to grow.  In areas where soil is compacted or degraded, add compost to holes prior to planting. Use clean compost (no manure or biosolids) to reduce the introduction of unwanted weeds during planting. The use of sphagnum peat moss should be avoided because of the impact on wetlands and the associated release of greenhouse gases.  Spread weed-free straw, bark, or wood chip mulch around the plants to reduce weed competition and to hold in moisture.  Irrigate the transplants thoroughly immediately after planting. Depending on weather, region, and site conditions, regular follow-up irrigation may be needed in the first year or two after planting but can be discontinued after establishment. Some non-native plants may require longer periods of irrigation.  Install netting or other plant guards where needed to protect transplants from browsing animals that can cause significant damage. Detailed guidelines for installing plant materials are found in Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat (FHWA 2017). If plant installation is conducted by contractors, it can be useful to include language in

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-32 contracts that outlines specifications for best practices. Arizona has an example of language for seeding specifications for contractors available at: https://apps.azdot.gov/files/roadway-engineering/roadside-dev/sample-class-ii-seeding- special-provisions_reference-only_adot-ido-roadway-roadside-development.pdf, and their best practices are outlined here: https://azdot.gov/node/5372. 7.4.4 Short-Term Management: Before and During Establishment Before installing plants, reduce competition with invasive, noxious, or undesirable plants that would otherwise pose a threat to the establishment of desired vegetation. Some DOTs, for example, include noxious and invasive species control in construction specifications so that those weeds are controlled before, during, and after construction. Remove weeds through herbicide applications or by repeated mowing. Focus on removing perennial weeds, which are harder to control after planting. Following planting, the site may require some management to keep annual weeds from seeding or to control any perennial weeds that were not eliminated before construction or planting. Additionally, in the first year of establishment, new seedlings require light and are greatly affected by weed canopies that stunt their growth. In this region, mowing to 8 inches high multiple times (2–4 times) in a growing season is often used to suppress annual weeds and help sunlight reach emerging wildflowers and grasses. Establishment mowing allows wildflower seedlings to better establish, survive, and flower in subsequent years (Williams et al. 2007; Meissen et al. 2019). For long-term success, weeds should be prevented from going to seed in the first 2 or 3 years. Care should be taken to properly identify weeds before removal; some young wildflower seedlings and weed seedlings may look alike. Common weed management strategies include:  targeted herbicide applications (e.g., spot-spraying or rope-wick treatments),  use of selective herbicides (e.g., grass-selective herbicides for grass weeds), and  strategic mowing (e.g., using a carefully timed high mow to target weeds). 7.4.5 Long-Term Management: After Establishment Plant communities need management over time to maintain species diversity and reduce encroachment by weeds or woody plants that may shade out plants in their understory. Practitioners generally follow these best practices in long-term management of plantings: 1. Assess the conditions on the ground. 2. Implement maintenance practices that help maintain wildflower diversity. 3. Consider flight and breeding periods of the listed and imperiled pollinators that are in the area when planning timing of maintenance activities. (See Chapter 6 for table of activity windows.) Weeds can limit native plant establishment by  limiting the light that reaches the new  seedlings, which grow more slowly than the  weeds in the first year after planting.  Photo Credit: Dave Williams 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-33 4. Evaluate the effects of maintenance activities in order to adapt and modify future activities based on experience. Within the framework of these practices, a combination of maintenance strategies can be used to maintain wildflower diversity. Practitioners agree that varying management activities is critical to encouraging wildflower diversity, but there is little agreement on how to vary practices, even within a region. Some managers are strong proponents of mowing mid-season to suppress warm-season grasses and stimulate wildflowers, while others suggest limiting mowing during the growing season so that wildflowers can reseed. This discordance underscores the value of adaptive management approaches that are tailored to address the conditions of a particular revegetation project. Table 7-6 provides an overview of common issues related to managing a diverse plant community, along with options that can be used to address these issues. (Note that more than one of these management options can be relevant to any site.) Table 7-6. Common long-term management issues for maintaining plant diversity. Issues / Concerns  Management Options  Cool‐season grasses  dominate in planting  Grass‐selective herbicide, mowing, or haying (or less commonly,  prescribed burning or grazing) at vulnerable grass growth stage (boot  stage, when the shoot is elongating and the seed head is developing  inside the shoot).  Warm‐season grasses  dominate over  wildflowers  Mid‐ to late‐summer grass‐selective herbicide or haying (or less  commonly, prescribed burning or grazing) at vulnerable grass growth  stage (boot stage).  Woody encroachment  Spot mow or cut brush in the spring or fall, apply an appropriate  herbicide to the cut stump, and follow up with prescribed fire if  woody plants resprout or sucker.   Maintaining  wildflower abundance  and diversity  Periodically hay or mow (at different times of growing season) or use  grass‐selective herbicides. (Less commonly, use prescribed fire in the  dormant season or graze rotationally, targeting active growth periods  of dominant grasses.)  Invasive weed  management  Use mowing or herbicides (or less commonly, prescribed burning or  grazing) to control invasives, timing management for when target  species are most vulnerable. 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-34 7.5 Case Studies  7.5.1 Adapting Design and Management in Washington Washington DOT is working to restore corridors of ROWs to design roadsides so that they look seamless with the surrounding landscape, as if no construction has taken place. To learn more about restoration of grasslands, Washington DOT is using the Scatter Creek Rest Area as a testing ground. Experiments are being conducted at the rest area to help inform seed mix designs and installation practices. By experimenting with drilling seed, broadcasting seed, and broadcasting with a furrow, Washington DOT is learning more about installation techniques that lead to the most successful native plant establishment. Washington DOT is also experimenting with timing of management to control invasive species that are present, such as scotch broom (Cytisus scoparius). Scotch broom is an introduced shrub that forms dense stands that can crowd out native plants and wildlife and is a difficult weed to control. In fact, scotch broom management can take decades because of the long-lived seeds that can germinate many years after falling from the plant. Washington DOT has also experimented with different management techniques, such as timing targeted herbicide sprays to scotch broom stems after mowing, or using prescribed burning to flush out the scotch broom seed bank. By monitoring pollinators and counting bumble bees, beetles, and other species, Washington DOT is gathering data that informs their design and maintenance practices regularly over time. 7.5.2 Roadside Plantings in New York for Monarchs along Their Migration Route As monarch butterflies in the Northeast fly thousands of miles south to their overwintering grounds in Mexico each fall, they often travel along the coastlines. In New York State, monarchs are frequently seen along the Ocean Parkway in autumn. As part of a coastal greenway project to develop a 10-mile shared use path along the shore between Captree State Park and Tobay Beach, New York DOT installed plants to support monarch butterflies in the median of the Ocean Parkway. In wide, open center medians, a layered planting system of native plant materials was developed. The interior section of the median was planted with a seed mix of wildflowers and grasses appropriate for the coastal region. The mix included species known to provide nectar for monarchs, including purple coneflower (Echinacea purpurea), smooth aster (Symphyotrichum laeve), and seaside goldenrod (Solidago sempervirens). Bayberry shrubs were planted around the perimeter of the planting. Landscape designers worked with New York DOT’s maintenance staff to determine when and where mowing should be avoided. Additionally, vertical mowing Camas (Camassia quamash) and other native  plants are filling in as invasive scotch broom  plants grow fewer with yearly treatments.  Photo Credit: Washington DOT  This layered planting along Ocean Parkway in  New York was designed to support monarch  butterflies, and it includes special mowing  markers to help maintenance know when to  mow.  Photo Credit: Crystal Peritz, New York DOT 

Chapter 7. Revegetation and Pollinators: Design and Implementation  7-35 markers were placed along the edge of the plantings, with words clearly marked, “Wildflower Area – Only Mow after 2nd Week of October.” 7.5.3 Revegetation focusing on Layers, Density, and Diversity Aesthetics is an important component of revegetation designs, but is secondary to creating a functional planting and healthy ecosystem. Massachusetts DOT Landscape Designer Tara Mitchell recommends focusing on ecological factors in order to create long- term, self-sustaining vegetation. Tara designs her plantings for resilience. For example, by selecting a diversity of species and plant types (ever-green, deciduous, herbaceous), plantings are more resilient to plant loss – both ecologically and visually. Tara selects species that are rapid colonizers so there is early plant cover, species like evergreens that provide winter habitat and aesthetic interest, and shrubs and understory trees to create layers. Layers of plant species of different heights and different rates of growth provide an attractive visual effect and more habitat. Tara also spaces plants relatively close together to create dense cover once established and to maintain coverage if some plants or species die. Along with layers, dense plantings provide better soil protection and helps shade out undesirable weeds. Tara has found that such plantings require less water and mulch during establishment, and that the survival rate of plants is very high, much higher than in trees or shrubs planted individually. 7.6 Resources   Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat: http://www.nativerevegetation.org/learn/manual_2017/  Ecoregional revegetation application tool: http://www.nativerevegetation.org/era/  Revegetation resource library: http://resources.nativerevegetation.org/  Plant lists for pollinators: https://xerces.org/publications/plant-lists In its fourth year of growth here, that same  planting has filled out so that plants are layered  effectively.   Photo Credit: Tara Mitchell, Massachusetts DOT  This planting, located between a main corridor  and a ramp, is in its second year of growth.  Photo Credit: Tara Mitchell, Massachusetts DOT 

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Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes Get This Book
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Transportation agencies can make a difference for imperiled pollinators by managing existing roadside vegetation and designing new revegetation plantings with habitat needs in mind. This can generate public support for agencies and help to mitigate the negative ecological effects of roads.

NCHRP Web-Only Document 362: Pollinator Habitat Conservation Along Roadways, Volume 5: Great Lakes, from TRB's National Cooperative Highway Research Program, is a 16-volume series. Each volume focuses on a specific region of the United States and is intended to provide relevant guidance to rights-of-way owners and operators for roadside vegetation management practices that support pollinators, as well as strategies that are compliant with the federal Endangered Species Act.

Supplemental to the document are a Dataset of Great Lakes Accessory Materials, a Communications Toolbox, a Conduct of Research Report, and a Video.

All the other volumes are available on the webpage for NCHRP Web-Only Document 362: Pollinator Habitat Conservation Along Roadways, Volume 1: Alaska.

The other volumes are:

Volume 1: Alaska

Volume 2: California

Volume 3: Florida

Volume 4: Great Basin

Volume 6: Hawaii

Volume 7: Inland Northwest

Volume 8: Maritime Northwest

Volume 9: Mid-Atlantic

Volume 10: Midwest

Volume 11: Northeast

Volume 12: Northern Plains

Volume 13: Rocky Mountains

Volume 14: Southeast

Volume 15: Southern Plains

Volume 16: Southwest

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