1A GuideHabitat Restoration and Native Plantingfor Maine Solar Developmentphoto: Dan jaephoto: Dan jaephoto: Dan jaephoto: Dan jae
2This guide was written by sta from Maine Audubon with generous review and input from the following: Regina Leonard of RSLLA, Josh Bastion of ReVision Energy, Jake Pierson of Pierson’s Nurseries, and ecologist, Adam Kohl. Illustrations by Rebecca Hoskins.
3TABLE OF CONTENTSINTRODUCTIONSTEPS TO WILDLIFE FRIENDLY VEGETATION MANAGEMENT AT SOLAR ARRAYSSITE SELECTION AND PLANNING 1. Site Assessment and Planning 2. Panel Height 3. Other Planning and Design ConsiderationsSELECTING AND PLANTING NATIVE PLANTS 1. Selecting Plants 2. Sourcing Native Plants a) Buers and Screens b) Underneath and Adjacent to the Project c) Other Plants to Consider Within and Around a Solar Array 3. Seed Mixes 4. Site Preparation and Weed Management 5. Timing 6. Sowing SeedsCOSTMAINTENANCE 1. Mowing and Best Management Practices 2. Applied Ecology 3. Pest ManagementOTHER CONSIDERATIONS 1. Fencing 2. Community EngagementAPPENDIX A: SAMPLE LIST OF MAINE NATIVE PLANTS FOR UNDER SOLAR ARRAYSAPPENDIX B: REFERENCES AND RESOURCESAPPENDIX C: COMPARISON OF NATIVE RANGES OF THREE FAMILIAR PLANT SPECIES57810181821
4Butterﬂies such as the Harris Checkerspot (pictured above) feed on nectar produced by many ﬂowers, but they will only lay eggs on the leaves of their caterpillar host species, Doellingeria umbellata (Flat-topped Aster, pictured above). Species such as Red-eyed Vireo (pictured above) depend on diverse and abundant host plants and caterpillars for successful nesting. NATIVE PLANTS ARE CENTRAL TO WILDLIFE REPRODUCTION AND FOOD WEBSFlat-topped Aster: ©Espace pour la vieWHY NATIVE PLANTS?
5Table of ContentsSolar arrays, if sited, planned, and managed properly, can provide quality habitat for birds, mammals, and other wildlife. This guide is for solar developers, landscape architects, and other professionals and individuals who are interested in designing solar arrays that maximize co-beneﬁts to wildlife and wildlife habitat through native plantings and site-speciﬁc design and management considerations.Incorporating native plant species is crucial to designing solar arrays that support wildlife, particularly birds and insect species. Native plant species host hundreds of adult butterﬂies and moths, especially in their larval stage, because the species have co-adapted together over millennia. Those caterpillars and other insects that rely on these plants are the primary food source for many bird species, another co-adapted taxa. The vast majority of birds that breed in Maine do so in early summer and rely exclusively on caterpillars to feed their chicks. What’s more, the pollen and nectar produced by native plants are critical to pollinators, which other animals depend on for food. It’s a virtuous cycle. Solar developers can support this cycle by choosing native plants over non-native species, which may feed adult pollinators, but may not fully support native butterﬂy, moth, and other pollinator reproduc-tion. Exotic plants such as turf grasses and common shrubs like lilacs and forsythia lack these connections and host plant relationships, thus do not support the reproductive cycles of Lepidoptera (butter-ﬂies and moths) or birds.This guide compliments other work by Maine Audubon, including “Best Practices for Low Impact Solar Siting, Design, and Mainte-nance—Avoiding and Minimizing Impacts to Natural and Agricul-tural Resources,” “Model Site Plan Regulations and Conditional Use Permits to Support Solar Energy Systems in Maine Municipalities,” and a “Renewable Energy Siting Tool.” Each of these resources, including this guide, is based on the premise that choosing the location of a solar project is paramount to successfully co-existing with wildlife and wildlife habitat. No amount of native planting can overcome the impact of locating a solar project on high value natural resources. We encourage readers to review the “Best Practices” and Maine Audubon’s “Renewable Energy Siting Tool” to better under-stand what high value natural resources to avoid when planning a solar project.INTRODUCTIONNative plants are central and foundational to food webs, connecting species and taxa that have evolved and co-adapted together over millennia.
7Step 1: Choose a site that avoids high value natural resources to the greatest extent practicable.Step 2: Assess the site and design the array to maintain existing habitats and habitat values, such as riparian habitat, high value soils, and native plants.Step 3: Work with a landscape architect to choose Maine native plants to revegetate and buer the site.Step 4: Plant the right native plants in the right places; use species that match the site’s growing conditions and size requirements.Step 5: Make sure habitat gains made through site selection, planning, and revegetation selection are not negated by subsequent maintenance (i.e., mowing and pest management).Step 6: Consider integrating additional bird and wildlife conservation measures into the array. These could include nest boxes, brush piles, and avoidance during nesting season.STEPS to WILDLIFE-FRIENDLY VEGETATION MANAGEMENT at SOLAR ARRAYS
81. Site Assessment and Planning Maine Audubon urges developers to prioritize avoiding wetlands and riparian areas, rare or exemplary natural communities, and unique habitats such as grasslands or rare plant habitat. We encourage solar developers to site panels and other project infra-structure in a manner that further avoids and minimizes impacts to natural features within the site.GIS, on-site evaluations, and other platforms can be used to identi-fy environmentally sensitive areas and other features. Conservation partners, such as the Maine Natural Areas Program, Maine De-partment of Inland Fisheries and Wildlife, Soil and Water Conser-vation Districts, Cooperative Extension, or local land trusts, can help developers identify priorities for particular projects. Maine Audubon recommends undertaking an assessment of invasive species at each site and implementing a management plan that addresses the reduction and elimination of these plants.In instances where high value soils are present at a site, eorts should be made to segregate and stockpile these soils for use after grading is completed. If rare or beneﬁcial native plants are present, care must be taken to conserve those populations, their local habitats, and their genetics. These sites must be developed more cautiously and conservatively and in collaboration with Maine Natural Areas Program.Many solar projects require grading throughout the project’s limits of work. Planning should include careful management of invasive plant species, topsoil conservation, and supporting native plant populations where possible. Soils brought into the site can also be a source of invasive plants and insects. SITE SELECTION AND PLANNINGphoto: Maine Natural Areas ProgramMaine is home to over 100 named natural community types, all of which serve as habitat for birds and other wildlife. Many of these natural communities are unique and therefore their beneﬁts are more specialized. In some cases, natural communities are classiﬁed as vulnerable, imperiled, or even extirpated. photo: Maine Natural Areas Program
9Revegetation and operational vegetation management at solar facilities are undertaken to meet a number of requirements. The selection of species, mowing regimen, invasive species management, stormwater permit requirements, and other aspects of vegetation management are all considered when determining the best vegeta-tion management regime.2. Panel HeightKeeping panels 4’ or higher will greatly expand the options for plant diversity. Roughly half of the 28 species listed in the table provided in Appendix A (page 24) are over 3’ in height. For an approximate one-time cost of around $3000 per megawatt per additional foot due to additional steel, having PV panels near waist-height allows for lower-cost seed mixtures and better vegetation establishment while reducing risk of mower-solar collisions. A panel height of 4’ or higher will also reduce potential shading from ﬁrst-year saplings, sprouts, and other advantageous vegetation. The amount of growth will vary depending on site characteristics and should be determined by an ecologist and considered in the plans. 3. Other Planning and Design ConsiderationsEnsure the general contractor uses an experienced partner hired for the vegetation design, installation, and management. The vendor should have demonstrated expertise in establishing and managing meadows.Place cables underground, if possible. Above-ground cables in a PV solar array block the rows, resulting in a signiﬁcant increase in string-trimming and mowing costs for the life of the asset.Include an adjustment/allowance for seed substitution at the time of permitting to avoid delays during construction and to provide ﬂexibility to reﬁne mixes in response to ﬁnal site conditions and seed availability.Each development site should be inspected by a qualiﬁed conserva-tion professional to document soil and other growing conditions. It is just as important to note invasive species pressure, what species might be expected to persist in the seed bank, other native species that might be valuable or return to the site, and the conditions of the edges of the project boundaries. This initial assessment will help to reﬁne the mixes as necessary. The approach to seeding should be zone speciﬁc and consider both the desired plant attributes as well as any regulatory requirements, such as coverage and maintenance standards.Plan for panel clearance heights of at least 3’ for native revegetation, while 4’ will enable signiﬁcantly more biodiversity and ease of maintenance.
101. Selecting Plants Most solar arrays consist of three dierent vegetation zones— within the array underneath the panels, within the array and out-side the panels, and buers/screens. Plants are selected for these zones based on height, spread, and other landscape functions. Areas within and adjacent to arrays are typically revegetated by seeding, while buers and screens are often planted with nursery stock.Many commercial seed vendors oer pollinator/wildlife friendly seed mixes tailored to solar arrays. Maine Audubon recommends selecting only naturally occurring native plant species (wild types, no named cultivar varieties) of Maine, ideally local ecotypes sourced from growers that avoid systemic pesticides and propagate naturally. Dozens of native plant species may be found commer-cially and can be grown under solar arrays, around the perimeter and other buer areas within the array, and as vegetative screens and buers outside the array.We refer to Biota of North America Program (BONAP) and Flora Novae Angliae as the deﬁnitive sources for historic ranges of plants. Of the roughly 3,800 species of plants historically native to Maine, the wild types of perhaps 150 species are being produced com-mercially. These are species that have occurred throughout Maine for centuries, most perform well in developed landscapes, and are cost-eective for vendors to grow in their natural form. These plants also have rich historical records of directly beneﬁting native wildlife, much of which can be referenced by genus and county using the Native Plants Finder (nwf.org/nativeplantﬁnder) hosted by the National Wildlife Federation.Within array ﬁelds themselves, panel heights of at least 3’ are required for minimum native plant diversity, and 4’ provides the most potential for appropriate biodiversity. Disturbed areas in between rows and outside the array should be utilized for taller species and greater diversity of native grasses and forbs.SELECTING AND PLANTING NATIVE PLANTS
112. Sourcing Native PlantsNative species can be sourced from a number of wholesale nurs-eries. Maine Audubon generally recommends purchasing smaller sizes that are easier to transplant and start growing faster than most mature plants, which often need a year or two to recover from transplanting. In cases where height is needed more immediately, many native species of trees and shrubs can be sourced in large sizes, but will require more equipment, expertise, and ongoing care (watering) than smaller transplants. The costs for pollinator mixes are comparatively high, and the establishment is more challenging than for typical conservation mixes. However, once established the plants will better stabilize the site and support wildlife habitat, as well as reduce annual mainte-nance costs.As more developers seek to use native plants and seeds, we will have a better understanding of costs, best practices, and results. Given what we do know about the horticulture industry, current seed availability, existing maintenance regimes, and ongoing investments, Maine Audubon and others expect that using native plants in solar arrays will provide signiﬁcant and direct savings for the developers and owners. a. Buers and ScreensVegetative buers and screens can provide beneﬁts that are practical, ecological, and aesthetic. Several species can be combined to ﬁll the viewshed, recreate edge habitat for nesting birds, and to engage communities in helping choose native ornamentals and heritage trees.Viburnum spp. 5-7 species of Viburnum are native to Maine, including V. dentatum (Arrowwood), V. trilobum (Highbush Cranberry), and V. lentago (Nannyberry), all of which are hardy medium-sized shrubs. Their large white early summer blooms are magnets for pollinators, followed by fruit enjoyed by birds and mammals later in summer.Hamamelis virginiana (Common Witchhazel) is a stunning, large spreading native shrub with distinctive leaves, which serves as a historic larval host for over 60 species of butterﬂies and moths. This is also one of the latest bloomers, serving as one of the few sources of nectar for pollinators still ﬂying in late fall.photo: Dan jae
12Thuja occidentalis (American Arborvitae) is an ancient ever-green tree with beneﬁts to both wildlife and people. Its foliage and fruit feeds dozens of species of caterpillars, birds, and mammals throughout the year. This species and genus have been modiﬁed to many named cultivars, which may not have the same beneﬁt as the wild type.Several species of Amelanchier, also known as Serviceberry or Shadbush, occur throughout Maine. Their distinctive white blooms throughout Maine’s forests and forest edges were an annual sign to the Wabanaki that ﬁsh—ﬁrst alewives then salmon and elvers—would be running in rivers and streams now. In landscapes to our West, without the connection to diadromous ﬁsh, the tree is known as Juneberry for the edible fruit that comes along that month. Myrica pensylvanica (Northern Bayberry): Several Maine native shrubs already stand up to our toughest, most exposed settings, like those left on the edges of large development proj-ects. Natural habitat such as sandy shorelines, windy moun-tainsides, and open shrublands makes bayberry well suited for a sturdy, beautiful, and beneﬁcial low screen/natural hedge staple in places with sandy, well-drained soil.Planted screens around solar arrays can help engage and enamor communities with beautiful native ornamental shrubs and trees, while not growing to heights that will shade panels nearby. From left to right, Amelanchier spp. blooms in April; Cornus spp. blooms in June/July; Hamamelis virginiana blooms in October; Viburnum spp. blooms in June; Clethra alnifolia blooms July/August. photo: A. Hainesphoto: Dan jaephoto: A. Haines
13b. Underneath and Adjacent to the ProjectMany species are suitable for planting within an array area, i.e., underneath and adjacent to panels, and also have practical, ecological, and aesthetic attributes.Zizia aurea (Golden Alexander) is a long-blooming and beau-tiful Maine native. It is one of the only native hosts for the larvae of Black Swallowtail butterﬂies, and also hosts the pollen specialist bees Andrena vernalis and Andrena ziziae.Penstemon spp. Several species of native beardtongues are easy to establish, tolerant of diverse growing conditions, and broad-ly beneﬁcial to numerous wildlife taxa. Most species grow to a maximum of 3 feet, enabling their use both within and outside of arrays.Schizachyrium scoparium (Little Bluestem): Maine’s native grasses and sedges are beautiful and beneﬁcial. Schizachyrium scoparium is a grass used widely as an ornamental, so is al-ready being grown and propagated commercially. This should be a staple of Maine seed mixes for sunny, well-drained loca-tions where it can be allowed to grow to 4 feet and self-sow.Asclepias spp. Milkweeds and their beneﬁts to Monarchs and other wildlife are well known, and most solar arrays could allow extensive habitat restoration for Monarchs, as well as for the direct restoration of Asclepias tuberosa, a native species of milkweed listed as potentially extirpated in Maine. This and two other native species of milkweed are available commercial-ly in bulk seeds and plugs, and should be dispersed together to adapt and colonize independently. c. Other Plants to Consider Within and Around a Solar ArraySolidago spp. Goldenrods are the top herbaceous host plant for larval Lepidoptera. Most species colonize readily, and many don’t exceed 4-5 feet tall. Goldenrods have varied bloom times, and those that bloom in September are a critical late source of nectar for Monarchs and Painted Lady butterﬂies, which need fuel for fall migrations.photo: Dan jaephoto: Dan jaephoto: Dan Jaephoto: Dan Jaephoto: Dan Jae
14Aster spp. Several genera make up the aster family, and Maine has dozens of native species. A number of species have been cultivated, and wild types have performed and germinated well enough to be grown commercially. New England Aster, Smooth Blue Aster, and Blue Wood Aster share the genus Sym-phyotrichum, and are tall plants that are common in native New England meadows. While some asters grow taller than 6 feet, they are an ideal native species for sites where invasive plants are being cut back in early summer before going to seed—the asters will still bloom, but will be 2–3 feet tall. Asters bloom late, making them critical sources of fall pollen and nec-tar followed by seeds.Ceanothus americanus (New Jersey Tea) is threatened in Maine, yet appears to be well adapted to landscapes that are becoming warmer and drier. This is a beneﬁcial shrub and only reaches 2-3 feet in height. It has a very deep and complex root system, which stabilizes soil well and has enabled the plant to survive ﬁres historically and, similarly, periodic mowing pres-ently. Seeds and plugs are available commercially, but perhaps not at the scale of seed mixes. Vaccinium angustifolium (Lowbush Blueberry), Myrica gale (Sweetgale), Comptonia peregrina (Sweetfern), and Spiraea spp. are other examples of low-growing woody plants with tremendous wildlife beneﬁts.3. Seed MixesSeeds are the most economical, and often the most sustainable, way to restore native plants to a site with exposed earth. Maine Audubon and several regional vendors are developing and reﬁning commercial-scale seed mixes comprised of native grasses and forbs for high pollinator and wildlife value. Seeds can be procured in bulk as either individual species or in mixes of several species combined by growing condition or to ac-commodate widely varied conditions. Most native species require cold stratiﬁcation due to a chemical inhibitor found outside the seed. A full winter of freezing and thawing is required for these seeds to germinate. An example of dierent mix types for dierent areas of a solar project:Mix #1. A native Maine mix of grasses and forbs for use beyond the array ﬁelds.photo: Dan Jaephoto: Dan Jaephoto: Dan Jae
15Mix #2. A native Maine mix of grasses and forbs for areas in and under the array.Mix #3. An alternative mix for use within array ﬁelds using natural-ized species. The lower cost mix includes cool season species to provide quick cover to meet permitting requirements as well as legume species for its pollinator value and site stabi-lization characteristics. This mix can also be supplemented with strategically located pockets of Mix #1 to enhance the diversity of native pollinator species.Sourcing wild varieties of native seeds and plants which are propagat-ed naturally at the scale required by most projects can be a challenge. Increasing numbers of reputable conservation vendors have emerged in New England and beyond, and some are working speciﬁcally to accommodate this relatively new demand. Maine Audubon recom-mends the following large-scale seed suppliers:• New England Wetland Plants• Ernst Conservation Seeds• Prairie Moon• Prairie NurseryWithin the array, variations in sunlight and moisture enable diverse low-growing native plants to thrive. Herbaceous species such as Aquilegia canadensis (Eastern Columbine), Zizia aurea (Golden Alexander), Rudbeckia hirta (Black-eyed Susan), and Echinacea purpureum (Purple Coneﬂower), as well as woodies such as Myrica gale (Sweetgale) and Ceanothus americanus (New Jersey Tea), all grow in varied soil and light conditions and grow to a maximum height of three feet or less.
164. Site Preparation and Weed ManagementBecause the usual revegetation objective is to change the species composition, particularly when invasive and/or weed species are present, control of the existing vegetation and seed bank well in advance of the seeding is often required. Suppressing weed compe-tition is particularly important. If weed pressure is high, then more than one strategy and/or more than one growing season may be needed. High weed pressure conditions include the following: 1) Persistent, year-round cover of undesirable plants; 2) Sites where weeds have been actively growing for multiple years; and 3) Sites dominated by introduced sod-forming grasses. (Previously cropped lands or regularly mown ﬁelds generally have lower dormant weed seed pressure.) Proper weed management and seed bed preparation prior to seeding will yield higher success rates in establishing the targeted plant community.Manage weed growth and prepare the site based on the conditions prior to seeding using one of the following methods:• Non-persistent herbicide. Control through non-persistent herbicide application is most common for larger solar sites; however there may be cases where organic site preparation methods are more appropriate.• Organic controls. Of the alternative methods for organic site preparation, repeated shallow tillage or soil inversion are the most appropriate techniques for larger solar sites. Techniques such as solarization and licensed application of herbi-cide combined with a targeted mowing regime can be employed to remove invasive and aggressive non-native vegetation and encour-age growth of desirable species.5. TimingSeeding should occur after the installation of the solar panels is completed. Seeding after grading and before post and panel in-stallation will result in poor soil to seed contact due to displaced soil from equipment movement. Plan for the least amount of time between project completion and seeding, so as not to enable other seeding in. Solar site development permits require a high thresh-old of 90% cover prior to agency sign-o. This standard can be challenging considering the slower establishment period for most warm grass and forb (wildﬂower) seedlings. The use of nurse and companion plants should help address this standard.Native plants can be naturally propagated from seed onsite, primarily via seeding in late fall or early winter. Many sites will require management of exotic weeds, which often outcompete native plants, particularly while they are being reestablished.
17In the Northeast, there are two seeding periods: • Spring. Spring planting should not occur until soil tempera-tures are above 65°F but should be completed before the end of June.• Dormant Fall Seeding. Seed should be broadcast in the fall when soil temperatures are below 55°F to avoid risk of germination, generally beginning in November, but before soils freeze. Seeding rates may need to be increased by 25% for dormant seeding due to lower germination rates and loss of seed consumed by wildlife over the winter months. However, dormant seeding may improve the establishment of many wildﬂower species the following spring due to exposure to cold conditions breaking dormancy.Warm season native bunch grasses germinate in midsummer when soil temperatures are between 65-70 degrees—much later than most broadleaf weed species and cool season grasses, and many wildﬂowers need several seasons to ﬂower and establish. Sowing in late fall is ideal for most native species to germinate the following spring, so projects that conclude their work in the fall are ideal. Consider temporary seeding/mulching as necessary so that per-manent seeding can be conducted during the appropriate seeding periods. Provide quick, temporary cover with nurse crops and com-panion plants during wildﬂower and warm season grass establish-ment to help reduce weed competition.• Nurse crops. Nurse crops include small grains like oats and cereal rye which are applied at 1/3 the typical rate. The cover crop will need to be mowed TO 3-4” height at milk stage with a ﬂail type mower.• Companion plants. Integrate fast growing, very small-seeded grasses like red top, wild ryes, and hard fescues into the mix in small quantities as companion plantings. For pollinator mixes, add Schizachyrium scoparium (Little Bluestem) for well-drained sites or wild rye for moist sites.6. Sowing SeedsSowing native wildﬂower and grass seed is similar in technique and equipment to other large-scale sowing/broadcasting and drill-seeding. Care should be given to roughen the surface, water in the seeds, and/or lightly cover (over-covering inhibits germination) with straw or spray mulch to protect from birds and other grani-vores. Choosing species that are already well-adapted to your site and dispersing them naturally should go a long way toward rees-tablishing those species after installation is complete. Fertilization is not recommended because it favors exotic species; most native species are adapted to low nutrients.
18The costs for pollinator mixes are comparatively high, and the establishment is more challenging than for typical conservation mixes. However, once established the plants will better stabilize the site and support wildlife habitat, as well as reduce annual mainte-nance costs.As more developers seek to use native plants and seeds, we will have a better understanding of costs, best practices, and results. Given what we do know about the horticulture industry, current seed availability, existing maintenance regimes, and ongoing investments, Maine Audubon and others expect that using native plants in solar arrays will provide signiﬁcant and direct savings for the developers and owners. These plants do not entail royalty payments for horticultural geneticists, are produced economically, and require less water and fertilization to adapt to local conditions than species developed via and in interdependence with the large turf technology industry. Habitat gains made during development must not be negated by subsequent maintenance choices. A vegetation management plan should be developed and implemented on a site-by-site basis and may depend on equipment and funding available. The following are guidelines for maintenance visits and timelines:• Season One. There will be little to no ﬂowering in the ﬁrst season. The goal is to control weed density, height, and seed setting during establishment and in future years, not to elim-inate weeds. Initial mow of cover crop during the milk stage to 3-4” height. Following this, mow when the vegetation reaches 12-18” tall to a height of 6-8”.• Season Two. Conduct a complete site mowing when the vegetation reaches 12-18” height, typically mid-June to early July. This mow will cut down competition from annuals, cool season grasses, and broadleaf weeds. Inspect the site during subsequent visits and spot mow and selectively apply herbi-cide or seed as needed.• Seasons Three and Beyond. As the meadow reaches matu-rity, initiate adaptive management: inspect the site and spot treat as needed. Mow one third to one half of the site annu-ally, rotating thirds or halves every year. Phase mowing will allow varying stages of development to increase plant diversi-ty and structure.MAINTENANCECOST
19Maintain the site using appropriate equipment that minimizes compaction, such as mid-sized tractors with harrows, ﬂail mowers, broadcast seeders, and chisel plow/box blades.A successful mowing plan will both cut invasive species before they produce seeds and allow for the intended native species to go to seed for their ongoing persistence. In sites where there are invasive spe-cies of plants, early mowing may be employed to prevent ﬂowering and seeding of those plants.For sites with less pressure from undesired plants, mowing can be limited to one third to one half of the site annually, rotating thirds or halves every year. Phased mowing will allow varying stages of devel-opment to increase plant diversity and structure. Timing of mowing and other maintenance is important to avoid dis-turbance to grassland birds and other wildlife. Spring and summer are primary nesting and brood rearing seasons, and maintenance should ideally be avoided at these times. Fall mowing avoids nesting season and can help with seed dispersal.1. Mowing and Best Management PracticesLimiting mowing to one to two times per year can both provide the safest habitat for birds, insects, and other wildlife and can help the project meet the Maine Department of Environmental Protection’s stormwater rules. Mowing is needed to manage unwanted plants, such as invasive species and woody successional plants which may throw shade on, or come in contact and interfere with, the panels, and can often be employed as needed, rather than regularly/annual-ly. The timing and scope of these regimes can vary site to site. Mow one third to one half of the site annually, rotating thirds or halves every year. Phase mowing will allow varying stages of devel-opment to increase plant diversity and structure. The following best management practices are recommended for mowing: • Once established, timing of maintenance is important to avoid disturbance to grassland birds and other wildlife. April 1 through August 1 are primary nesting and brood rearing seasons, and it is recommended that maintenance is limited at these times. In the Northeast, Maine Audubon recommends mowing between September and October.• Once established, rotate mowing as speciﬁed to increase plant diversity and structure. If possible, leave 10-15% of the area undisturbed as refugia, which are important for insect conservation.Annuals and some short-lived exotic plants can be used as nurse or cover crops to supplement fall seedings of Maine native plants. For example, Chamaecrista fasciculata (Partridge Pea) is a North American native that beneﬁts pollinators and builds soil nutrients, and can be sown in warm months.
20• Spot mowing to control noxious weeds can be done any year to ensure planting health, even during establishment years. It focuses on speciﬁc problem areas distinct from mowing the entire site during establishment.• Use a ﬂail type mower rather than a sickle mower, which tends to lay over plants and smother germinating wildﬂowers. Projects will undoubtedly have intrusion from exotic species and un-desirable native trees such as sumac, birch, and ash that lead forest succession. Spot pruning or periodic mowing of intruding woodies may be necessary throughout the life of the array, while certain areas should be identiﬁed to use the two mowings as part of the manage-ment plan speciﬁcally.2. Applied EcologySolar arrays can be developed in ways that restore habitat, but the landscape will have to be actively managed to meet the varied goals. Practices that align with plant life cycles will be most eective and may eliminate other maintenance. For example, an array with an area where knotweed is intruding in an otherwise healthy wildﬂower meadow should be mowed low twice before the plants bloom, while the rest of the array may not need any mowing in some years. Simi-larly, fall mowing might also be supplemented with seeding to native perennials and spring mowing might be employed to aid dispersal of native wildﬂowers whose seeds have remained over winter. These are cases where the maintenance/mowing is aiding the ecology.3. Pest ManagementWe recommend avoiding the use of systemic pesticides, such as ne-onicotinoids, which kill insects indiscriminately. The use of defoli-ants in wetlands and other sensitive areas should be avoided to allow for the development of the highest quality habitat and least nega-tive impacts. Avoid systemic, regimented applications of fertilizers or pesticides and instead focus direct spot treatments on critically impacted areas. Traditional pest management practices applied to a site to which insects and other wildlife have been attracted will increase the collateral damage compared to a site where insects and wildlife are not as prevalent.If exotic weeds and invasive species cannot be managed eective-ly mechanically, Maine Audubon recommends an Integrated Pest Management approach. Application of non-persistent herbicide is most common for larger solar sites, however there may be cas-es where organic site preparation methods are more appropriate. Of the alternative methods for organic site preparation, repeated shallow tillage or soil inversion are most appropriate techniques for larger solar sites. Organic site preparation can take several years to implement.Most solar arrays will require longterm vegetation management, at least to prevent woody succession. Healthy populations of native plants that grow to 3-4 feet or less can improve ecological beneﬁts and help reduce maintenance costs.
211. FencingThe National Electric Code requires fencing for certain sized, ground-mounted solar energy systems. To maximize wildlife’s ability to permeate fencing, Maine Audubon recommends using ‘Solid Lock Game Fences’. Such fencing would start with 8- by 12-inch openings at the bottom (ground) with progressively smaller openings at the top of the fence. This type of fencing meets the National Electric Code for human safety. To allow for wildlife passage, fences should be elevated by a minimum of 5 inches. Additionally, we recommend placing ﬁve-inch or larger diameter wooden escape poles in two or more corners of the perimeter fence as an alternative means for wildlife to escape the enclosed area. Fencelines should be monitored regularly for wildlife that may be trapped inside the array, and to conﬁrm the fence is allowing wildlife to pass while keeping people out.Standard best practices for wildlife-friendly fencing at solar arrays are still in development through ongoing discussions among state and federal natural resource agencies. We recommend contacting Maine Audubon, the U.S. Fish & Wildlife Service, or Maine Depart-ment of Inland Fisheries & Wildlife for the most up-to-date recom-mendations.Fencing can provide structure for climbing species of beneﬁcial na-tive plants like Clematis virginiana (Virgin’s Bower), Parthenocissus quinquefolia (Virginia Creeper), and Vitis labrusca (Fox Grape), as well as for upright perennials to lean on. Tall species such as Sym-phyotrichum novae-angliae (New England Aster) and Eutrochium maculatum (Joe Pye Weed) planted under a fence will grow tall clumps on both sides, proving an eye-catching and ecological way to enclose a project. 2. Community Engagement While safety is of paramount importance, some sites may be condu-cive to individuals and small groups performing periodic community science and/or other maintenance and monitoring activities which may in turn garner additional community involvement and support. Some examples of community engagement around wildlife and habitat include: • Community science opportunities, such as those related to breeding birds, insect decline, Monarch Butterﬂy conservation, and migrationOTHER CONSIDERATIONS
22• Including conservation technology within the project, such as radio telemetry, which is used to track migrating birds, bats, and insects• Seasonal surveys, such as “Bio Blitzes”, of speciﬁc taxa led by botanists and/or ecologists, which can inform subsequent planting, seeding, and maintenance • Nesting boxes for bees and birds, though additional care must be taken to manage for invasive species like House Sparrows, which exploit these resources
23ReferencesCenters for Pollinators in Energy, Fresh Energy. 2021. Best Practices and Training. Retrieved from https://fresh-energy.org/beeslovesolar/best-practices-and-trainingKalland, S., Andeck, Pollinator-friendly Solar and G., Davis, R., Meinschein, G., Simenson, M. Part II: Pollinator-friendly Solar: A Technical Practi-cum (2017, October 24). [Webinar]. NC Clean Energy Technology Center. https://youtu.be/jdLgh9Kdayw?t=4146Michiana Area Council of Governments, North-ern Indiana. January 2020. Technical Guide: Establishment and Maintenance of Pollina-tor-Friendly Solar Projects. Retrieved from http://macog.com/docs/sustainability/ solar_energy/Pollinator-Friendly- Solar-Guide-Version-1-1.17.2020.pdfUMass Clean Energy Extension, University of Massachusetts Center for Agricultural, Food, & the Environment. 2019. Best Management Practices for Pollinator-Friendly Solar Arrays. Retrieved from https://ag.umass.edu/sites/ag.umass.edu/ﬁles/pdf-doc-ppt/pollinator_friendly_bmps_for_solar_arrays.pdfUS Department of Agriculture (Maine). 2018. Pollinator Habitat Development, Maine Job Sheet for Herbaceous Plantings for Conservation Cover (327) or Field Border (code 386). Retrieved from https://efotg.sc.egov.usda.gov/api/CPS-File/14272/386_ME_IR_Field_Border- Pollinator_Habitat_2015APPENDIX A: REFERENCES AND RESOURCESResources for “Bringing Nature Home” in MaineBiota of North America Program’s North American Plant Atlas (for reference on native ranges) http://bonap.net/NAPA/Genus/ Traditional/CountyGo Botany: Native Plant Trust (for species ID and speciﬁc/current range information)https://gobotany.nativeplanttrust.org/Maine Audubon “Bringing Nature Home” Projecthttps://www.maineaudubon.org/plantsMaine Audubon Native Plant Finderhttps://mainenativeplants.org Maine Natural Areas Program (for Rare Plants in Maine, Natural Communities and Ecosystems, Invasive Plants in Maine) https://www.maine.gov/dacf/mnap/features/ National Wildlife Federation Native Plant Finder (featuring historic record of host plants by zip code) https://www.nwf.org/ NativePlantFinder/PlantsPollinator Partnership and North American Pollinator Protection Campaign (NAPPC). Selecting Plants for Pollinators: A Regional Guide for Farmers, and Gardeners in the Eastern Broad-leaf Forest Oceanic Province Bioregion. Retrieved from https://www.pollinator.org/PDFs/ EasternBroadleaf.Oceanic.rx18.pdf
24APPENDIX B: SAMPLE LIST OF MAINE NATIVE PLANTS FOR UNDER SOLAR ARRAYS SCIENTIFIC NAME COMMON NAME NATIVITY BLOOM MAX SHADE MOISTURE (nearest states if not ME) TIME HEIGHT TOLERANT? REQUIRED Aquilegia canadensis Red Columbine ME Spring 2’ yes medium Asclepias syriaca Common Milkweed ME Summer 4-5’ no medium Asclepias tuberosa * Butterﬂy Weed ME?, MA, NH Summer 3’ no dry Baptisia tinctoria ** Wild Yellow Indigo ME?, MA, NH Summer 4’ no dry Carex spp. *** Sedges ME Spring 4’ or less variable variable Chamaecrista fasciculata Partridge Sensitive pea MA Summer/Fall 3’ no dry Eurybia divaricata White Wood Aster ME Fall 3’ yes dry Eragrostis spectabilis Purple Lovegrass ME Fall 2’ no dry Geum canadense White Avens ME Spring 4’ yes medium Ionactis linariifolia Sti Aster ME Fall 5’ no dry Juncus tenuis Path Rush ME Summer 1’ yes dry Lespedeza capitata Round-Headed Bush Clover ME Summer 4’ no dry Lobelia siphilitica * Blue Lobelia ME?, MA, NH Fall 3’ yes medium Lupinus perennis Sundial Lupine ME?, MA, NH Spring 3’ no dry Penstemon digitalis Foxglove Beardtounge ME Spring 5’ no dry Penstemon hirsutus Northeastern Beardtounge ME Spring 2’ no dry Pycnanthemum tenuifolium Narrow-leaved Mountain Mint ME Summer 4’ no dry Schizachyrium scoparium Little Bluestem ME Summer 4’ no dry Rudbeckia hirta var. hirta Black-Eyed Susan MA Summer 4’ no dry Sisyrinchium angustifolium Narrow-leaf Blue-eyed Grass ME Spring 2’ no dry Solidago bicolor White Goldenrod ME Fall 3’ no dry Solidago juncea Early Goldenrod ME Summer 4’ no dry Solidago nemoralis Gray Goldenrod ME Fall 3’ no dry Solidago puberula Downy Goldenrod ME Fall 4’ no dry Sorghastrum nutans **** Golden Grass ME Summer 5’ no dry Symphyotrichum laeve Smooth Aster ME Fall 5’ no dry Symphyotrichum lateriﬂorum Calico Aster ME Fall 3’ some dry Zizia aurea Golden Alexanders ME Spring 3’ some medium
25SCIENTIFIC NAME COMMON NAME NATIVITY BLOOM MAX SHADE MOISTURE (nearest states if not ME) TIME HEIGHT TOLERANT? REQUIRED Aquilegia canadensis Red Columbine ME Spring 2’ yes medium Asclepias syriaca Common Milkweed ME Summer 4-5’ no medium Asclepias tuberosa * Butterﬂy Weed ME?, MA, NH Summer 3’ no dry Baptisia tinctoria ** Wild Yellow Indigo ME?, MA, NH Summer 4’ no dry Carex spp. *** Sedges ME Spring 4’ or less variable variable Chamaecrista fasciculata Partridge Sensitive pea MA Summer/Fall 3’ no dry Eurybia divaricata White Wood Aster ME Fall 3’ yes dry Eragrostis spectabilis Purple Lovegrass ME Fall 2’ no dry Geum canadense White Avens ME Spring 4’ yes medium Ionactis linariifolia Sti Aster ME Fall 5’ no dry Juncus tenuis Path Rush ME Summer 1’ yes dry Lespedeza capitata Round-Headed Bush Clover ME Summer 4’ no dry Lobelia siphilitica * Blue Lobelia ME?, MA, NH Fall 3’ yes medium Lupinus perennis Sundial Lupine ME?, MA, NH Spring 3’ no dry Penstemon digitalis Foxglove Beardtounge ME Spring 5’ no dry Penstemon hirsutus Northeastern Beardtounge ME Spring 2’ no dry Pycnanthemum tenuifolium Narrow-leaved Mountain Mint ME Summer 4’ no dry Schizachyrium scoparium Little Bluestem ME Summer 4’ no dry Rudbeckia hirta var. hirta Black-Eyed Susan MA Summer 4’ no dry Sisyrinchium angustifolium Narrow-leaf Blue-eyed Grass ME Spring 2’ no dry Solidago bicolor White Goldenrod ME Fall 3’ no dry Solidago juncea Early Goldenrod ME Summer 4’ no dry Solidago nemoralis Gray Goldenrod ME Fall 3’ no dry Solidago puberula Downy Goldenrod ME Fall 4’ no dry Sorghastrum nutans **** Golden Grass ME Summer 5’ no dry Symphyotrichum laeve Smooth Aster ME Fall 5’ no dry Symphyotrichum lateriﬂorum Calico Aster ME Fall 3’ some dry Zizia aurea Golden Alexanders ME Spring 3’ some medium * Extirpated (S-rank: SX), potentially extirpated (code: PE) in Maine** Historical (S-rank: SH), potentially extirpated (code: PE) in Maine*** Choose species that work best for the site**** Extremely rare (S-rank: S1), endangered (code: E)NOTES
26Acer pensylvanicum (Striped Maple): This Maine native forest understory tree also makes a striking small ornamental tree in diverse growing conditions.Acer circinatum (Vine Maple): This species is also commercially available as an ornamental tree for cold hardiness zones like Maine, but its native range is on the West Coast.Acer ginnala (Amur Maple): This popular and widely available ornamental tree is exotic to North America and becoming invasive.Species present in state and nativeSpecies present and not rareSpecies present and rareSpecies not present in stateSpecies present in state and exoticSpecies exotic and presentSpecies noxious (includes noxious weed seeds)MAP COLOR KEYphoto: Gail Hampshirephoto: Dan jae* From Biota of North America ProgramAPPENDIX C: COMPARISON OF NATIVE RANGES OF THREE FAMILIAR PLANT SPECIES*photo: ThayneTuason
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