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photo of a bee on flowering plants and roadside wildflowers

November 2016

U.S. Department of Transportation - Federal Highway Administration

Cover Photo
Photo credits: Jeff Norcini, Idaho DOT, Jennifer Hopwood/ The Xerces Society

Technical Report Documentation Page

1. Report No.

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Identifying the Current State of Practice for Vegetation Management Associated with Pollinator Health and Habitat: An Interview Report

5. Report Date

November 2016

6. Performing Organization Code

7. Author(s)

Jennifer Hopwood, Scott Black, and Scott Fleury

8. Performing Organization Report No.

9. Performing Organization Name and Address

ICF International
ICF Incorporated, L.L.C.
9300 Lee Highway
Fairfax, VA 22031

Xerces Society for Invertebrate Conservation
628 NE Broadway, Suite 200
Portland, OR 97232

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-11-00033/TO 5001

12. Sponsoring Agency Name and Address

Federal Highway Administration
1200 New Jersey Ave SE
Washington, DC 20590

13. Type of Report and Period Covered


14. Sponsoring Agency Code


15. Supplementary Notes

Contracting Officer's Representative: Deirdre Remley, FHWA, HEPE-20, 202-366-0524,

Pollinators are critical to our food supply as well as to the health of ecosystems. Wild pollinators such as the monarch butterfly and a number of bumble bee species are in decline, and beekeepers in the United States and Europe have reported significant losses of managed European honey bee colonies. Pollinator declines are attributed to loss of habitat, pesticide exposure, diseases, parasites, and effects of introduced species. Roadsides can benefit pollinators by providing foraging habitat, places to breed, nest, and overwinter, and may act as corridors, linking patches of fragmented habitat.

This report documents interviews with roadside vegetation managers and designers in nine State Departments of Transportation, conducted in 2014, to inform transportation managers about the state of the practice in protection and establishing pollinator habitat in roadsides.

17. Key Words

pollinators, integrated vegetation management, butterflies, bees, bats, moths, nectar, host plants, roadside habitat, reduced mowing, native plants, roadside landscape design, roadside maintenance

18. Distribution Statement

No restriction. This document is available to the public from the sponsoring agency at the website

19. Security Classif. (of this report)


20. Security Classif. (of this page)


21. No. of Pages


22. Price


List of Tables and Figures

Acronyms and Abbreviations


Summary of Interview Responses
Current Roadside Management Practices of State DOTs
Roadside Habitat for Pollinators – Current Practices that are Benefiting Pollinators
Constraints on Improving Roadside Habitat for Pollinators
Tools Needed for Change

Final Thoughts

Appendix A

Appendix B

Appendix C

Appendix D


  1. Roadside Vegetation Management Tools Used by State DOTs
  2. Frequency and Timing of Roadside Mowing by State DOTs Interviewed
  3. Examples of How State DOTs Incorporate Native Plants into New Roadside Plantings
  4. State DOTs that Currently Adjust Roadside Maintenance Practices to Reduce Impacts on Rare, Endemic, or Sensitive and Declining Pollinators

Acronyms and Abbreviations

DOTs Departments of Transportation
FHWA Federal Highway Administration
IRVM Integrated Roadside Vegetation Management
ROW Right-of-way, Rights-of-way
USFWS U.S. Fish and Wildlife Service


In February of 2015, the Xerces Society for Invertebrate Conservation and ICF International interviewed staff from State departments of transportation (DOTs ) and roadside restoration experts who work with DOTs to document existing roadside vegetation management practices and obtain feedback from those professionals about the feasibility of implementing roadside vegetation management strategies that can benefit pollinators. When selecting the interviewees, we sought out professionals from different geographical regions. This report describes information obtained from the interviews on the state of practice in roadside vegetation management as relates to pollinators, highlighting both successes and challenges in improving pollinator habitat.

We used several criteria to identify individuals to interview. The DOT representatives we interviewed were selected either from States where some pollinator-friendly roadside management practices are already being implemented, or from States that have expressed an interest in implementing pollinator-friendly practices. In our selection of restoration ecologists with expertise in roadside habitat, we focused on leaders in the field who understand the science, practice, politics, and economic issues that are related to roadside vegetation management as well as pollinator conservation.

Sets of questions were developed to distribute to the interviewees. Our questions were derived from the findings of a literature review of peer-reviewed and technical material on the topic of vegetation management to enhance pollinator habitat value (Hopwood et al. 2015). The literature review found that adjusting vegetation management techniques to accommodate pollinator resource needs, as well as enhancing and restoring native vegetation to roadsides, are key steps to improving the quality of roadside habitat for pollinators. Additionally, modifications to the frequency, timing, and scale of vegetation management practices and roadside native plant revegetation can help to mitigate some of the threats associated with roads that pollinators face.

Specific findings on how roadside vegetation management can improve the quality of roadsides as habitat for pollinators include:

  • It is ideal for pollinators if roadside vegetation is mown no more than twice during the growing season.
  • It is important to time mowing to minimize disruption to the life cycles of rare, endemic, or sensitive and declining species of pollinators.
  • Mowing in autumn or after first frost will benefit a variety of pollinators by allowing flowering plants to bloom uninterrupted throughout the growing season and will reduce the risk of mortality by mower to larval stages that reside on vegetation (e.g., butterfly caterpillars, larval flower flies).
  • Herbicide use, and subsequent impacts of herbicides on pollinators, can be reduced through the use of selective herbicides, spot-spray applications, and timing of applications to the plants during life stages when the weed is most vulnerable.
  • Training provided to roadside managers about the timing and selection of chemicals for particular weeds, weed identification, and native plant identification can also reduce the amount and frequency of herbicide use.
  • Integrated roadside vegetation management (IRVM ) can benefit pollinators by employing limited, judicious use of mowing and herbicides.
  • If cattle, sheep, or goats are used to graze invasive weeds on roadsides, consider the timing of the life cycles of rare, endemic, or sensitive and declining species of pollinators.
  • If fire is used, consider rotational burning of every 3 to 5 years, which allows time for pollinator populations to recover.
  • Native plants on roadsides sometimes face threats from pesticide drift from adjacent land, intentional herbicide use, or excessive mowing or haying from landowners living adjacent to roadside rights-of-way (ROW ).
  • Specific findings on the value of using native plants for revegetating or restoring roadsides include:
  • Native plants can be an effective roadside vegetation management tool.
  • Native plants can provide effective erosion control, buffer against invasive non-native weeds, are adapted to local conditions, require fewer inputs, reflect a region’s natural heritage, and support more wildlife, including pollinators.
  • Pollinators are more abundant and diverse on roadsides with native plants.
  • When designing revegetation projects, planners can select native species that are adapted for particular site conditions, which will establish more successfully than a general regional mix.
  • Plans that include a diversity of flowering plants with sequential and overlapping bloom times will provide resources for pollinators throughout the growing season.
  • Plants used for revegetation can include host plants for butterflies (e.g., milkweeds for monarch butterflies) and can provide pollen and nectar for a wide range of pollinator species.
  • Based on these findings, two sets of interview questions were created to distribute to our interviewees. The interviews for DOT personnel consisted of 31 questions, and the interviews for restoration experts consisted of 18 questions. Although some interview questions were asked of both DOT personnel and restoration experts, there were also unique questions posed to each group to reflect their varying expertise. Our questions fell into these categories:
  • General policies and procedures for roadside management,
  • Current practices that benefit pollinators,
  • Opportunities and constraints for pollinator-specific roadside management practices, and
  • Opportunities and constraints for increasing the value of new roadside plantings to pollinators.

The specific interview questions that were distributed to State DOT personnel are included in Appendix A, and the questions that were distributed to roadside restoration experts are included in Appendix B. The surveys were distributed via email, and one-hour follow-up telephone interviews were scheduled. Most, but not all, of the individuals whom we interviewed returned written responses to the interview questions, in addition to the verbal responses provided during the telephone interviews.

We conducted one-hour telephone interviews with 27 individuals, including 20 individuals from nine State DOTs, as well as seven individuals with expertise in roadside restoration ecology. The nine State DOTs interviewed included Arizona, California, Florida, Idaho, Iowa, Ohio, Oregon, Minnesota, and New York. A list of the DOT representatives we interviewed can be found in Appendix C, and a list of the restoration experts we interviewed is included in Appendix D.

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Summary of Interview Responses

The information we obtained from the interviews fell into four main categories: 1) current roadside management practices used by State DOTs, 2) current practices that can benefit pollinators, 3) limitations to implementing additional practices to benefit pollinators, and 4) what is needed to overcome limitations and improve roadside habitat for pollinators.

Current Roadside Management Practices of State DOTs

Of the nine of the State DOTs we interviewed, five—California, Iowa, Idaho, Oregon, and New York—have formal IRVM programs that are supported by policy, training, and guidance documents. The four agencies interviewed without a formal IRVM program—Arizona, Florida, Ohio, and Minnesota—report using aspects of IRVM. Both Arizona and Minnesota mentioned that a lack of formal policy and centralized structure have led to uneven implementation of IRVM across their States. Training to support the use of IRVM ranged from the basics, such as Florida’s training on mechanical and chemical controls, to more extensive training that includes plant identification for maintenance staff and routine training for design staff, as in New York.

The roadside vegetation management tools that are most often employed by the State DOTs interviewed include, from most used to least: mowing, herbicide use, brush removal, native vegetation, biological control, fire, and grazing. All nine States used mowing, herbicides, brush removal, and native vegetation as roadside vegetation management tools (Table 1). Biological control is used by six States, prescribed burns are used by five States, and grazing is used by two States (Table 1).

Table 1. Roadside Vegetation Management Tools Used by State DOTs

State DOT


Herbicide Use

Brush Removal

Native Plants

Biological Control

Prescribed burns






















New York



Mowing was identified as the tool most frequently used by the State DOTs that we interviewed. All the States use mowing to maintain a clear zone. Mowing is also used by all States to varying degrees to maintain the roadside vegetation from the clear zone to the fence. The frequency and timing of mowing of the entire roadside right-of-way varies between States and also within some States (Table 2). Four States (Iowa, Ohio, Minnesota, and New York) limit mowing of the entire right-of-way to a maximum of once a year, with mowing typically taking place either in mid-summer or in the fall. Idaho and Oregon limit mowing of the entire roadside to a maximum of twice per year. Mowing in these States takes place in the late spring and early fall, or mid-summer and early fall. Mowing of the entire roadside can take place throughout the year in Arizona, California, and Florida. In Arizona and California, roadsides may be mown in certain regions for fuels reduction to avoid wildfires. In urban areas, roadsides are typically mown more frequently to accommodate the perceived aesthetic preferences of drivers. For example, in and around highly populated parts of Florida, the roadsides are mowed up to 20 times a year (i.e., as often as every 18 days).

Table 2. Frequency and Timing of Roadside Mowing by State DOTs Interviewed

State DOT

Frequency of Mowing of the Entire Roadside in One Year

Timing of Mowing


Exact number not provided

Throughout the year


Limit mowing when possible (some areas need to be mowed to reduce fire risk)

Spring and summer



Throughout the year



July 15 - September



Early July, late October






Late spring, early fall



Within the month of August

New York


At discretion of regional maintenance offices

Table 3. Examples of How State DOTs Incorporate Native Plants into New Roadside Plantings

State DOTs that Reported Prioritization of Use of Native Plants

Examples of Uses of Native Plants


New projects include 15–25 ecoregional native species (3–5 species are grasses, the rest are forbs and some shrubs).


Erosion control projects are 99% native species; landscape projects include 40–60% native species.


All plantings except shoulders, medians, and urban areas are entirely native.


Most new plantings include native species (and introduced). Some projects are entirely native species.


Plantings in rural areas are nearly entirely native, with an emphasis on ecoregional species of native forbs and grasses. In urban areas plantings may be more ornamental but still use some natives.

State DOTs that Reported No Prioritization of Use of Native Plants

Examples of Uses of Native Plants


Increasing the use of native plants.


Conducting several trials of prairie plantings in areas without high weed pressure.


30% of new plantings are native, 70% are planted with a pasture mix of nonnative species.

New York

Use natives when cost-effective and practical. About 50% of shrubs and trees used are natives, while seeded areas are usually planted with nonnative turf species.

Insecticides are rarely used in roadside management programs. Minnesota DOT and Oregon DOT only use insecticides to treat certain trees in the rights-of-way if the trees are at risk due to invasive pests. California DOT has used insecticides on roadsides for vector control or to limit the spread of invasive crop pests, for example, spraying roadsides near orchards or vineyards with insecticides to control the glassy-winged sharp shooter (Homalodisca vitripennis). Based on our interviews, the primary chemicals employed by State DOTs for road maintenance are road salts. All States interviewed excepting Florida DOT use road salts in winter months.

At the time of the 2015 interviews, none of the State DOTs were considering adjustments to roadside management to support pollinators in general. However, all noted that some of their current practices provided collateral benefits to pollinators (e.g., use of native plants). When we followed up with the interviewees in 2016, multiple DOTs had taken steps to trial or implement changes in vegetation management practices with the explicit purpose of increasing the value of roadside habitat to pollinators. For example, New York DOT began a pilot project to examine reduced mowing, while Ohio DOT started a voluntary once a year mowing program, and Florida DOT incorporated consideration of pollinators into their Wildflower Program Procedure.

Where federal or state listed endangered or threatened pollinator species are present, State DOTs must work with the United States Fish and Wildlife Service (USFWS ) and/or State departments of wildlife, which regulate listed species, to develop management plans and obtain permits for impacts. Six of the nine States have adjusted roadside vegetation management practices to reduce harm to pollinators protected by State or federal law (Table 4). For example, when beginning new construction projects, Arizona develops plans with specifications to salvage and relocate agave and saguaro, plants that are critical to the endangered lesser long-nosed bat. Oregon DOT maintains special management areas on its roadsides for three federally listed butterflies, Fender’s blue butterfly, Oregon silverspot butterfly, and Taylor’s checkerspot butterfly.

In 2015, no transportation agency personnel interviewed were aware of a State or local law that mandated pollinator habitat protection. However, Oregon DOT was aware of Oregon’s Pollinator Health Task Force, a directive of the governor. The Task Force recently published draft recommendations, one of which stated that “ODOT should develop a plan for using native plant material along transportation corridors to establish pollinator habitat on public land.” Following the governor’s 2016 executive order, Minnesota DOT began to pursue ways to improve roadside pollinator habitat, including increasing the use of native plants.

Table 4. State DOTs that Currently Adjust Roadside Maintenance Practices to Reduce Impacts on Rare, Endemic, or Sensitive and Declining Pollinators

State DOT

Rare, Endemic, or Sensitive and Declining Pollinator

Conservation Status


Lesser long-nosed bat (Leptonycteris yerbabuenae)

Endangered (Federal listing)


Monarch butterfly (Danaus plexippus)

None at present


Frosted elfin butterfly (Callophyrus irus)

Endangered in DE, MD, NH, OH; Threatened in CT, MI, NJ, NY, WI; Species of concern in MA, RI


Poweshiek skipperling (Oarisma poweshiek)

Endangered (Federal listing)


Fender’s blue butterfly (Icaricia icarioides fenderi)
Oregon silverspot butterfly (Speryeria zerene hippolyta)
Taylor’s checkerspot butterfly (Euphydryas editha taylori)

Endangered (Federal listing)
Threatened (Federal listing)
Endangered (Federal listing)

New York

Karner blue butterfly (Lycaeides melissa samuelis)

Endangered (Federal listing)

When asked whether roadsides managed as pollinator habitat is compatible with driver safety, DOT personnel all indicated that it would be safe for drivers if certain considerations were met. For example, recommended safety measures include keeping vegetation within the clear zone mown regularly adjacent to roadside pollinator habitat, and maintaining low stature vegetation in high-crash zones. DOT personnel also recommended consideration of site-specific factors during the design stage when planning revegetation projects; for example, avoiding the use of tall vegetation within the lines of sight at intersections and around curves. Lastly, DOT personnel felt that the presence of managed honey bee colonies on roadside rights-of-way would likely be a safety concern for drivers who veer off the road as well as for maintenance crews, and suggested that beekeepers could locate their hives on land adjacent to but not on rights-of-way so their bees could forage on the roadside habitat without posing a risk to drivers or maintenance crews.

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Roadside Habitat for Pollinators – Current Practices that are Benefiting Pollinators

Identifying and Managing Existing Roadside Habitat

Remnant habitat is very valuable to pollinators. Inventories to identify intact existing roadside remnant habitat not only serve to protect existing habitat, they can save money that might be unnecessarily spent on excessive management. Several States have conducted inventories to identify remnant roadside habitat and recognize the value of that habitat by managing it with care. “The wildflowers are already there,” a State DOT representative told us. “We just need to stop mowing them down.” One of the restoration ecologists we spoke with observed that, “Sometimes [these roadside sites] just need a good burn or mowing to return as beautiful natives.” Florida, one of the most biologically diverse places in North America, has recently adopted a new procedure to focus on identifying naturally occurring wildflower areas and management approaches for those areas.

Reduced Mowing Frequency

Outside of urban areas, most States we interviewed mow the entire roadside from clear zone to fence line only once or twice per growing season (Table 2). State DOTs have various reasons for limiting mowing, including economic savings, reduced emissions, and benefits to nesting grassland birds. Mowing roadside vegetation no more than twice per growing season also helps to maintain the quality of roadside habitat for pollinators. Although in 2015 no State DOTs expressly limited mowing to benefit pollinators, in 2016 some States trialed reduced mowing for that purpose.  Several DOTs noted that increased value of roadsides to pollinators was an incidental advantage of reduced mowing, though not in their view the primary advantage.

Roadside mowing in some parts of Florida occurs frequently, which has caused controversy with some residents. Jeff Caster, State Transportation Landscape Architect with Florida DOT, describes the situation: “Environmentally conscious citizens called us to complain that we were mowing down wildflowers and butterfly habitat. There would be butterflies on the side of the road feasting on the native vegetation and we would come in and mow it all down and we would get people naturally upset with us.” A creative solution emerged over time: a public partnership. Florida DOT isn’t able to respond to a garden club or individual that wants less roadside mowing. Instead, if citizens in a certain county want less roadside mowing to preserve existing stands of wildflowers, they are asked to bring Florida DOT a “wildflower resolution” approved by that County’s board of commissioners. Then Florida DOT will develop a mowing plan to accommodate the resolution. A model resolution can be found on the Florida Wildflower Foundation’s website ( Now, 27 out of Florida’s 67 counties have moved to adopt wildflower resolutions. These counties “make a commitment to saying they want to enjoy the visibility of wildflowers for whatever reason, some do it to attract nature-based tourism, some doing it to help their farms, for whatever reason,” Castor says. “Some are very specific in their resolutions where they want to make a wildflower corridor. Others authorize their public works department to identify areas to convert because they are anxious to get this process going but haven’t had the time to actually identify places.” If successful, Florida’s unique grassroots approach to protecting wildflowers at the county level also has great potential for pollinator conservation.

Managing Noxious and Invasive Weeds

The prevalence of noxious weeds and invasive species on roadsides reduces pollinator abundance and diversity. Eradicating or reducing noxious and invasive weeds can improve the quality of habitat for pollinators. Managing noxious weeds is a priority for all of the State agencies interviewed. Additionally, some States also attempt to control invasive species that are not on their noxious weeds list, or make special efforts to eradicate weeds following disturbances caused by construction projects. For example, Minnesota DOT works to control Queen Anne’s lace (Daucus carota), a species that is invasive but is not yet considered noxious by State law. In its construction specifications, Arizona DOT stipulates control of noxious and invasive species prior to and following disturbance of sites during construction projects. This practice allows the newly planted desirable species to establish quickly and successfully.

Using Native Species

Native species of wildflowers, grasses, shrubs, and trees have been used successfully in roadside plantings, according to the people we interviewed. In some States, the use of native species is routine. Arizona, Iowa, and Oregon have been using native species extensively for several decades. These States have worked with plant material vendors to increase species availability and have partnered with local agencies and experts to increase the success of establishment. LeRoy Brady of Arizona DOT highlighted an approach that helped the DOT increase the availability of native species: work with seed suppliers to grow or collect seeds for certain species and pay 20-30 percent above market value on those species. Iowa has a requirement to use local ecotype seed in county and State roadside plantings. Dr. Laura Jacksonf the Tallgrass Prairie Center and Professor of Biology at the University of Northern Iowa, told us that that the commercial seed industry pays close attention to specifications, so when Iowa DOT specified local ecotype seed, it really helped to drive change within the industry. Oregon is currently redesigning its seed mixes to be ecoregionally specific, to accommodate the State’s varying hydrology and climate. The use of local ecotype plant material not only increases the chances that a planting will establish successfully, it also ensures that plant material is well-adapted to the site. Pollinators that depend on flowering resources at specific times will benefit greatly from roadside plantings that use local ecotype plant materials.

Ohio has very little roadside remnant habitat that remains intact. Most roadsides in Ohio are predominately planted with nonnative cool-season grasses, but Ohio has recently undertaken several roadside restoration projects using native plants. These pilot plantings, led by Ohio DOT’s Dianne Kahal-Berman in District 9, were undertaken expressly to provide pollinators with habitat. Kahal-Berman began the project after learning of pollinator declines. She told us that losing pollinators like bees was an unacceptable scenario, given the crucial role of pollinators to our food systems. Kahal-Berman felt that DOTs could play a key role in reversing declines by providing education to the public, generating excitement, and managing DOT land to support pollinators. Kahal-Berman began her project by locating sites for restoration that were not overtaken by invasive species and in areas that were very visible. She also sought out internal and external support, holding stakeholder meetings in the area to provide some education and engagement. Although the program is in beginning stages, she says that there has been great response, both internally at Ohio DOT and from the public. In 2016, Ohio DOT became a partner in the new Ohio Pollinator Habitat Initiative, an effort to create habitat and raise awareness. 

Several of the people we interviewed highlighted the multiple benefits of native species. Carmelita Nelson told us of a Minnesota DOT study that found that diversity in roadside vegetation helps to prevent driver drowsiness and safety. Bonnie Harper-Lore, a restoration ecologist now retired from the Federal Highway Administration (FHWA ), told us of a handwritten letter received from a truck driver that thanked FHWA for all of the wildflowers along the road, to which he credited with keeping him awake throughout his long drives. Aesthetics and state natural heritages were advantages of native plants that were highlighted by several transportation agency personnel. Other personnel interviewed brought up the importance of well-established native plantings in reducing invasions by noxious weeds, and providing habitat for pheasants and songbirds. Noting that erosion control is the primary reason for planting roadside vegetation, Harper-Lore highlighted native plant contributions to soil stabilization, and observed that plantings of native forbs and grasses form a matrix of vegetation that can hold even the steepest of slopes. Reduced runoff and improved water quality were other benefits of using native species that were brought up in the interviews.

Research demonstrates that pollinators are more abundant and diverse on roadsides with native plants. DOT staff and restoration experts view value to pollinators as one of many benefits of using native plants in revegetation efforts. Staff from several different State DOTs emphasized that the value to pollinators was an additional way to promote the use of native plants for roadside revegetation. One of the restoration specialists we spoke with told us, “The fact that for so long a lot of DOTs have planted monocultures that need to be mowed all the time has really cost them lots of time and money. If we can add native plants in rights-of-way, it will help every ecosystem.”

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Constraints on Improving Roadside Habitat for Pollinators

Funding Constraints

The State DOT personnel we interviewed consistently mentioned that a lack of funding was a constraint to providing both IRVM as well as adjusting roadside management to better support pollinators. All DOT personnel noted that DOTs are underfunded and that the money they do have first goes to roads and bridges. “There is no money for landscape budgets, so what would need to happen is specific funding dedicated to establishing native plants on the roadsides,” said one DOT representative. Another DOT representative told us that “the biggest overarching problem with this [IRVM] program is budget cuts and staff reductions, and the feeling that this is an optional program.” Additionally, few States have funding for roadside inventories. One DOT representative said that although they are certain that their State has remnant roadsides there are no resources to identify the remnant habitat.

Constraints to Reducing Mowing

In a few States we interviewed, intensive mowing is the primary method of managing most of their roadsides. Of the State transportation agencies we interviewed, Florida had the most intensified mowing program, with roadsides in some portions of the State that are mowed up to 20 times a year. Roadsides that are mown so frequently would not support pollinators. Jeff Caster of Florida DOT has been pushing for change within his agency: “We did a research project that looked at the ecosystem services provided by the unpaved portions of the highway system, and benefit to pollinators was just one of the ecosystem services the landscape provided. The study indicated that if we reduced mowing, the ecosystem services would be greatly enhanced and we could get more benefit from it.” The study also found that Florida could save significant amounts of money by reducing mowing. Despite these positive findings, Florida DOT was extremely wary of reducing mowing. After some internal negotiation, everyone agreed to trial a 10 percent reduction in mowing. Although a 10 percent reduction translates to mowing some sites every 20 days rather than every 18 days, Castor views this as a significant beginning.

Several of the transportation experts who were interviewed mentioned that some States are not open to simple changes like reduced mowing. The culture within the agency can play a role, based on the feedback we received from the DOT personnel that we interviewed. A DOT representative said of the mowing within their state, “in my opinion 50 percent of mowing is ineffective and is a cost that should not be incurred but it happens because of lack of knowledge and expertise.” In some States, recommendations for mowing may come from the turf management programs at State universities, which encourage the DOT to fertilize and mow often to maintain the roadside as turf. Several people interviewed voiced a need for guidance or directives from FHWA on reduced mowing, while others felt that directives were needed but would be most effective if they came from governors or local representatives.

Intensive mowing also occurs in urban areas within States that have reduced mowing in rural areas. Consistently, our interviewees mentioned that people in urban areas tend to tolerate wildflowers less than turf. Cathy Ford of Idaho Transportation Department told us that there was some pressure to maintain more manicured roadsides around cities, even in areas that received little rainfall. Wildflowers can be viewed acceptable as long as they are in bloom and kept tidy by a regularly maintained clear zone, according to some interviewees.

Another mowing-related issue in California, Iowa, and Minnesota is the mowing of roadsides for hay by citizens. Although Iowa and Minnesota have laws in place on when roadsides can be mowed to protect ground-nesting birds, citizens do not always conform to those State regulations or other restrictions set by roadside authorities. Haying might take place multiple times during a growing season or is cut so short that wildflowers cannot recover. Joy Williams of Iowa DOT, Tina Markeson of Minnesota DOT, and Carmelita Nelson of Minnesota Department of Natural Resources all noted that such haying practices can be very disruptive to pollinators as well as other wildlife.

Constraints on Timing of Mowing

Reducing mowing of the entire roadside (pavement to fence line) was identified by multiple States as one of the biggest opportunities for changes that could benefit pollinators (alongside the increased use of native wildflowers), as well as the biggest challenge. State DOT personnel were open to the idea of receiving guidance about the best time to mow to benefit pollinators, but emphasized the need to have some flexibility about when to mow. Many pollinators, including monarch butterflies that migrate south in the fall, would benefit from mowing that takes place after the first frost. From the perspectives of our interviewees, there are downsides to this timing. For example, delaying mowing until the fall allows any weeds present during the growing season to go to seed. Iowa, Minnesota, and New York also stressed that postponing mowing until the fall would be difficult because there is a need to shift maintenance staff from summer work to training and preparing equipment for snow and ice work as winter approaches. Joy Williams from Iowa DOT told us that equipment needs to be in “winter mode” by October 15. Tina Markeson from Minnesota DOT said that the State’s delayed-mowing law already creates a sense of urgency among maintenance staff to get as much mowing done as possible in August. Carmelita Nelson reiterated that point, noting that if staff were told that mowing would have to be later than August, they would feel more pressure from also needing to get ready for winter. Mike Shippey of Oregon DOT also mentioned weather constraints in the fall, noting that although it would be the best time to mow from a natural resources perspective, the agency’s limited staff could not mow all the roadsides in the short window of time that the weather would allow.

Several restoration experts pointed out that mowing during the growing season, although it can be harmful to some pollinators, can also benefit pollinators by rejuvenating wildflower populations. “The reality is that it [a roadside] has to be mowed sometime. If it remains unmown year after year, they [roadsides] will grow into trees,” according to one roadside restoration expert we interviewed. Another reiterated the point, saying, “There is some benefit to mowing on roadsides because flowers will rebloom. If you don’t do any mowing, there will be fewer pollinators because there will be fewer flowers out there. Cutting back actually helps. If you are aiming for herbaceous species, you have to mow at least once a year to keep the woodies out.”

However, our interviewees also highlighted the difficulty in finding a time during the growing season to mow. “It has to be a compromise between birds, bunnies, and butterflies, and something is going to get killed,” said one roadside restoration expert. New York, Minnesota, and Iowa DOTs all currently aim to time their mowing to reduce impacts on birds and bats. A DOT representative said, “Pollinators are important, but this needs to be looked at holistically with the other things we are tasked to do. Like avoid mowing during bird nesting season or avoid this and avoid that. It gets complicated fast.” Another DOT representative underscored this idea as well, mentioning that scheduling work can be very difficult with competing regulations: “State law says we must use the most cost-effective or ecological control strategy [to maintain roadsides]. Well, that means if you use herbicides, they must be used when most effective, but then the endangered species law trumps that and we need to use something else at the wrong time of the year to get around that.”
These interviewees emphasized that although there are benefits to mowing laws that restrict timing, there are also unintended consequences. A restoration expert said that ultimately, when it comes to timing mowing to benefit wildlife, “there really is no one right, good answer. You just have to do your best. It is a balancing act.”

Constraints on Modified Herbicide Use

Efficient and effective herbicide use, along with avoiding damage to nontarget plants and reducing exposure to pollinators, can reduce the impacts of herbicides to pollinators. However, DOT personnel noted a number of constraints. For example, limited staff time was frequently cited as a constraint to fine-tuning herbicide applications to maximize herbicide effectiveness and reduce ecological impacts. While some States work to time applications of herbicides to be most effective, limited staff and resources mean that not all weeds are treated at the optimal time. Additionally, keeping applications on target can sometimes be a challenge. Many DOTs use booms to apply herbicides. Some booms are designed to provide a highly targeted spray pattern and dispense large droplets, which limits the likelihood of drift, while other equipment can increase the likelihood that nontarget vegetation (and as a consequence, pollinators) is impacted by applications. One DOT described hose reels used for spray applications from trucks, observing that definition of spot spraying was different than most: “We do spot spraying, but the spots are larger than if you are using a backpack. Our definition of a spot is 400sq ft.”

Very few of the States we interviewed provide their maintenance staff with training to identify native vegetation. Although some States recognize the value of such training, funding and time to develop and deliver the training is not available.  A roadside restoration expert pointed out that as a consequence, “Road authorities can’t always tell what is what. If they see purple, they see noxious thistle. They don’t know that it is a blazing star or some other good plant.” A DOT representative noted that native thistles, highly beneficial to pollinators, are often mistaken for invasive thistle species. Finding time, expertise, and resources for training were all mentioned as constraints to reducing herbicide use through the identification of native vegetation.

Constraints on Use of Native Plants

When asked to name management changes that they think would benefit pollinators the most, the people we interviewed most often cited increasing the use of native plants, as well as modifying mowing regimes. However, eight of nine State DOTs also identified the cost of native plant material as an obstacle. For example, Cathy Ford, Idaho DOT, told us that there are many native species that she cannot purchase because costs of some wildflowers reach over $100 per pound. With budget limitations, Ford is only able to purchase a small amount of wildflower seed. Firecracker penstemon and western prairie clover, wildflower species Ford mentioned that she’d like to use because they establish easily and are great for pollinators, are too expensive for most projects. Availability of species is also an issue. For example, there is only one native seed vendor in Ohio, which limits the locally sourced plant species available to Ohio DOT. In Idaho, Ford emphasized that there are many wildflowers she’d like to be able to use, such as native asters and milkweeds that are not available in sufficient quantities. As a consequence, Ford has access to a limited subset of native wildflowers with a limited range in bloom times.

But even in States such as Minnesota where there are multiple seed vendors that can supply large quantities of many native species, cost appears to be restricting the use of native species in roadside plantings. According to Tina Markeson of Minnesota DOT, the expense of native seed is one of the reasons why only 30 percent of new Minnesota DOT plantings use native vegetation. Designers and builders within the department feel the cost is too expensive to justify. If cost was not a factor, there would be more wildflowers, Markeson told us.

Bonnie Harper-Lore reiterated the constraints surrounding seed availability and costs. She mentioned two efforts she undertook while working at FHWA to attempt to increase seed supplies, including a legislative proposal to give no-interest loans to seed growers that ultimately did not pass, and a national conference to encourage seed growers to share workable strategies for increasing seed availability.

Additionally, the process of establishing native plants can be a barrier. New York DOT has little experience with the establishment of native wildflowers, although they are comfortable establishing native trees and shrubs. Their limited experience makes them hesitant to use native wildflowers in erosion projects or revegetation efforts. Similarly, Ohio has interest in establishing more roadside plantings using native plants, but does not yet feel comfortable with the establishment and maintenance processes.

Another limitation to increasing the use of native plants is the perception of native plants by the public. For example, one roadside restoration expert noted that “One of the limitations I see is many of these county roadsides are by farmland and you find roadside managers going through all the effort to get forbs out there. The farmers see the flowers as a threat so they go out and spray with herbicides.” A DOT representative echoed that thought: “One of our biggest problems is selling the idea of using native plants on the roadsides to farmers.” In contrast, another roadside restoration expert felt that farmers were more likely to be receptive to wildflowers in roadsides than people in urban areas, because they could see the direct value of having pollinator and beneficial insect habitat near their crops. In their experience, noted a restoration expert, “You have to make the financial and functional case as best you can, and some people will be receptive to that and others not.”

Lack of Expertise

Six agencies highlighted knowledge gaps within their agencies as examples of a lack of expertise to manage roadsides as a natural resource. Florida, for example, mentioned that Florida DOT does not employ any biologists, and in order to conduct roadside inventories, they must hire contractors. Though New York DOT has great experience with planting trees and shrubs, they do not have expertise when it comes to wildflower establishment. In Minnesota, there is a fairly large knowledge gap in the ability of maintenance personnel to recognize the weed versus a beneficial wildflower, according to Carmelita Nelson. One DOT representative told us, “Our guys know how to mow but don’t have the knowledge of plant ID or cultivation. We don’t have landscape architects, horticulturists or botanists on staff.” According to Bonnie Harper-Lore, Ohio had trialed a project to plant native wildflowers about 15 years ago, but weren’t familiar enough with restoration and native species to recognize that they had purchased a species mix primarily composed of annual flowers with origins outside of Ohio, including species from Europe. As a result, the planting only lasted a single year, and the failure set back attempts to plant wildflowers in the State for some time.

In Florida, Dr. Jeff Norcini and Jeff Caster of Florida DOT provided another example of the impact a lack of expertise can have on roadside habitat and pollinators. The frosted elfin butterfly, an imperiled species, uses host plants in the bean family, and particularly prefers sundial lupines. In a right-of-way adjacent to Florida Forest Service land where both lupines and frosted elfin butterflies were present, the DOT agreed to suspend mowing until after the lupines present bloomed and dispersed seed, which usually occurs by June 1. After June 1, mowing resumed on a 30-day cycle, and as a result, the mowing caused severe soil compaction and suppressed other native plants. Although the frosted elfin had habitat during its flight period, the habitat quality for pollinators and other wildlife was highly diminished for the rest of the growing season. A natural resources contractor visited the site and recommended that the site could be restored by mowing the roadside only as necessary to prevent encroachment of woody vegetation and through regular monitoring and spot treatment of invasive species.

“I think there is a lack of expertise especially because there is a perception that this [roadside revegetation with native plants] is easy - just pull seed off the shelf and throw it on the ground. In reality, it is just like being an engineer, with training needed,” said a roadside restoration expert.

Overspray/Drift of Herbicides from Adjacent Land

Off-target herbicide applications can damage roadside plantings, which can reduce the habitat quality for pollinators and other wildlife and also increases opportunities for weeds to invade the planting, further decreasing its quality. Joy Williams of Iowa DOT explained that this type of damage can occur in roadsides adjacent to private land when boom sprayers are not turned off as sprayers turn around at the edges of fields in the process of applying herbicides to herbicide-resistant crops. One roadside restoration expert said, “I would say we need to focus on areas either adjacent to landowners yards where they will take care of it and not spray it, an organic farm, park or public area or even a church where the site will not be regularly sprayed.” Several restoration experts as well as DOT personnel noted that communication with adjacent landowners and education around the value of native plants can decrease intentional spraying or mowing of native plants by private landowners.    

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Tools Needed for Change

Increased Support within State Agencies, Support from FHWA, and Support from the Public

Transportation agency personnel universally mentioned their need for increased support from within their agency and State, as well as from FHWA (“buy-in from top to bottom,” as one person said) to make roadsides more pollinator-friendly. All interviewed were interested in improving roadside habitat for pollinators, but were also thinking more broadly about the stewardship role of DOTs and managing roadsides as conservation lands. For example, several of the people we interviewed felt that environmental stewardship belonged in the mission statements of their agencies, as well as in FHWA’s mission statement.

Currently, natural resources are not a priority for State DOT agencies, according to the people we interviewed. The focus on safety and efficiency overshadows the natural resource value of roadsides, which receive little thought and few resources. One DOT representative said, “The main interest is pavement and getting people from here to there. Other things are incidental.” Other DOT representatives also expressed concern that ecological roadside management can be difficult to implement when crews are tied up with other priorities. Better coordination and communication between functional units is also necessary, said another DOT representative. “Environmental and Landscape Architecture divisions may implement a great planting, but if Maintenance is uninformed, the benefits may be lost.”

Because maintenance staff personnel perform a wide range of duties, several people interviewed suggested that specific staff be dedicated to the purpose of managing roadside vegetation. “For DOTs to do anything significant on their roadsides will require some way to empower them, and to separate [vegetation management] from their maintenance crews. The work is [currently] done by the same people that patch holes and fix cracks and everything else,” said a DOT representative. “In the priority of things, vegetation falls low on the priority list and it is hard to get the time and resources to do it well.”

Regarding the process of revegetating roadsides, a roadside restoration expert told us, “I think you need to have people with biological backgrounds involved. It took us 10 years to get really comfortable with doing this work. I think if they have the biological sciences background, they can catch up pretty quickly.” Another roadside restoration expert agreed, saying “Having people dedicated to restoration on a permanent basis would be a tremendous advantage. This is a highly specialized field, and a lot of agencies don’t have the time or resources to do it successfully.” Personnel from DOTs agreed but one added, “If a transportation agency cannot dedicate staff to vegetation work, there still needs to be means to provide as much training and support as possible to the maintenance staff performing revegetation.”   

Some ideas proposed to increase support within DOTs include targeting and prioritizing plantings to improve success of restorations, increasing public support, and presenting data demonstrating the economic and ecological value of reduced mowing, judicious herbicide use, and use of native plants. Restoration experts we spoke with were very interested in encouraging the DOTs they work with to seek out remnant roadsides that through reduced mowing and simple management could become spectacular roadsides, visually and as habitat for pollinators. A roadside restoration expert told us, “It would take expertise to go out there and find remnant areas with a high probability of success, but it is easier to teach ground staff how to manage those areas than go in and plant a new area. Any Federal initiative around that has the probability for success.”

Additionally, restoration experts recommended that revegetation projects with native plants should be prioritized in areas with low to moderate weed pressure. Knowing that DOT staff typically have limited experience with restoration, they recommended deprioritizing work on sites that have high weed pressure, because these sites may take more time and expense to convert back to native vegetation. Restoration experts also suggested focusing efforts on the widest rights-of-way possible to maximize potential habitat. Experts also highlighted the value of locating restorations in areas highly visible to the public, in order to increase awareness. “You need to use both the economic and ecological approach to make selling this program palatable to the public,” said one roadside restoration expert. “But there also have to be areas with showy plants to wow the people driving at 60-70 miles an hour for a program like this to be successful. The best PR is having the showy stuff: color sells!” Jeff Caster of Florida DOT mentioned that some of the counties in Florida adopting wildflower resolutions were doing so because it supported tourism. Positive feedback from the public can also increase support within DOTs. Chris Jannusch from California DOT suggested that having a system to prioritize the placement of plantings would be very useful. For example, placing new native plantings next to almond orchards might receive higher priority because of ecosystem service benefits than using native plants in a cloverleaf embedded in a densely populated urban area.

LeRoy Brady from Arizona DOT, John Rowen from New York DOT, and Scott Lucas from Ohio DOT advised that internal support for pollinator conservation can be gained by highlighting the multiple benefits of using native plants. For example, an established stand of native grasses and wildflowers can resist weed colonization, which reduces the work and resources needed to control weeds. One DOT representative felt that proposing management changes based on benefits to pollinators was not enough: “Plants [to support pollinators] are a real benefit but are a component of an overall revegetation program to stabilize slopes to prevent erosion and reduce long term maintenance. You need to approach it from a point of how it benefits all aspects, and one of the important aspects is plants for pollinators.”

In addition to support from the public and from within their agencies, the people we spoke with wanted directives from government. Scott Lucas from Ohio DOT thought that in order to move forward in a meaningful way with making changes, the governor of the State would need to be engaged. Dianne Kahal-Bermen from Ohio DOT agreed but added that she thought that protecting pollinators through roadside habitat should be a non-partisan effort. Several people mentioned that guidance from FHWA would be helpful to the States. “Their leadership will have a huge impact on the States. If FHWA really starts pushing forward the whole idea of biological corridors, all the sand and gravel guys will get in line,” one DOT representative told us. “If FHWA and USFWS would start sending some strong messages to the DOTs around this, they would have a dramatic effect.” Another DOT representative said, “If FHWA issued a mandate or developed policy around pollinators and roadside pollinator habitat, it would really help us improve coordination between the design and environmental stages and maintenance.” Multiple DOT representatives mentioned that current Federal funding was too low to support the planting of wildflowers. A roadside restoration expert elaborated, saying, “There is a requirement that they [DOTs] plant native wildflowers [when using Federal funds] but it is such a small percentage of their budget [at a minimum 0.25 percent of the funds expended for landscaping] that it is almost meaningless. If they had to plant half of their erosion control landscaping control budget with native plants that would get their attention. Suddenly, they would have to find the expertise to make it happen.”

More Education and Training

Education and training were also universally mentioned as indispensable by transportation agency personnel and roadside restoration experts. The people we interviewed expressed a need for information in five areas:

  1. Native plant identification,
  2. Native plant establishment and management,
  3. Affordable, ecoregional species lists of plants that support pollinators,
  4. Importance of pollinators and their habitat needs, and
  5. Examples of targeted management changes to benefit pollinators.

Native plant identification
Native plant identification training was identified as a need for DOT design and maintenance staff, alongside noxious and invasive species identification.  Continuing education credits, which are required for herbicide applicators and their supervisors, could be an opportunity to incorporate education about plant identification and other pollinator-related training. If trainers obtain approvals from accreditation agencies to offer credits, this gives people an added incentive to attend training. In addition to formal training, materials and tools to aid with identification were requested from staff. Carmelita Nelson suggested that posters that can be hung in maintenance shops and Troy Seifert noted that pocket guides that can be stowed in trucks or tractors can be effective tools. Dr. Laura Jackson proposed using YouTube videos for education, but thought that ultimately, hands-on experience in the field is the most important. Dr. Jeff Norcini also proposed signage in wildflower areas to remind mowers to be careful.

Native plant establishment and management
DOT personnel also acknowledged that they were in need of information about native plant establishment and management. Scott Lucas of Ohio DOT admitted that they don’t have the internal expertise to establish and maintain native plantings on large scales. Lucas suggested that they might look into partnering with another organization that has experience (e.g., Pheasants Forever), so that his staff could work alongside their experts to learn and use it as a training period. Restoration ecologists underscored the value of training. One roadside restoration expert said, “Just because these are wildflowers does not mean they don’t need work until well-established. Training is critical to the success of revegetation.” Another roadside restoration expert told us, “You really need to understand what you’re working with. You need to understand the climate, the soils, and the vegetation. It does take time and money to figure it out but is doable. We have a process that we follow.” Another roadside restoration expert concurred, offering insights and tips for successful projects: “One of the things our team does is get involved with these projects two to three years before they are implemented. This allows us to collect seed, propagate, do soil surveys, look at the climate and work with the engineers to change plans. A lot of times when we do our initial study of a site, we often go back to the engineers and let them know what we foresee as challenges so we can try and approach it from a different angle. Time frame is really important. You need to have a minimum of a year to plan how to develop the site for it to be successful. One of the reasons for our success is having support top-to-bottom internally and from our funding sources that give us the ability to successfully implement projects we are involved with. The other thing that helps our success is one of us from the team being at the site during installation to ensure guidelines are followed. There is a lot of labor and love that goes into this.”

Affordable, ecoregional species lists of plants that support pollinators
Guides to affordable, ecoregional species lists of plants that support pollinators were highlighted as tools that would be useful. Cathy Ford of Idaho Transportation Department requested plant lists of commercially available species that include plant attributes, functional roles, and value to pollinators. Ecoregional lists of plants that could be used by DOTs would also be useful for farmers, gardeners, and restoration practitioners.

Importance of pollinators and their habitat needs
In order to understand the changes they are implementing, and justification for those changes, DOT representatives requested more information about the importance of pollinators and their habitat needs. They wanted to know more about the benefits of pollinators to agriculture for their own knowledge, and also to help sell their vegetation management programs. Joy Williams of Iowa DOT added that information about imperiled or listed pollinator species that might be present on roadsides would be useful, including their flight times and habitat needs. Oregon DOT’s Mike Shippey went a step further and suggested that if imperiled pollinators are utilizing roadside habitat, staff need proper training on managing those areas where the pollinators reside.

Examples of targeted management changes to benefit pollinators
Finally, people were interested in having concrete examples of targeted management changes that could benefit pollinators. Sample mowing regimes were one example put forth. Another person requested that this current project’s findings be incorporated into a webinar for transportation agencies.

Interviewees recommended that training and education on these topics should be available for the maintenance staff, design staff, engineers, and middle management of State transportation agencies. Many of the interviewees proposed that trainings should include other experts and state and federal land managing agencies that could share their knowledge and expertise. “We are interested in looking at the land management practices that other State agencies and private land owners are using. We feel doing so would be beneficial to the department and everybody,” one DOT representative told us. Additionally, everyone we spoke with was eager to connect with other peers. For example, another DOT representative said, “It would be very helpful to hear what nearby States have to say about these and the issues they are facing. Understanding what they are doing helps us in dealing with what we are up against.” Another DOT representative mentioned that at one point in their career, FHWA paid for travel for peer reviews of vegetation management programs, and they felt that exposure to the “tremendous amount of experience” of peers in nearby States was highly beneficial. Similarly, another DOT representative noted interest in learning from others: “I’m very interested in seeing what other States are doing and what is working for them in regards to pollinator habitat.”

Expanding Seed Markets

When asked if there were any additional thoughts they’d like to share about managing roadsides for pollinators, several of the people we spoke with mentioned concerns about native seed availability. Specifically, they were concerned about matching native seed to ecoregions. Before the State of Iowa put in place local ecotype seed specifications, Dr. Laura Jackson said there were “Wild West” conditions, where seed was procured without regard to its origin. Jackson is concerned that as the use of native wildflowers in roadside plantings increases in other States, the benefits of acquiring local ecotype seed will be overlooked in favor of cost savings. It would be a tragedy to miss out on the opportunity to capture local genetic variability, Jackson told us, and that opportunity shouldn’t be overlooked even if seed from other regions can be obtained much more cheaply. Bonnie Harper-Lore used the example of milkweed seeds being shipped around the country to illustrate her concern. She noted that species of milkweeds are being planted outside of their regions, with two possible undesirable outcomes. Some plants won’t be able to successfully establish and those plantings will fail, but others might succeed to such an extent that they become invasive and problematic. Planting ecoregional seed sources is critical to creating successful plantings and avoiding unintended consequences. One DOT representative proposed that Operation Wildflowers, a cooperative program between Garden Clubs, State agencies, and FHWA, might be a creative way to gain ecoregional foundation seed that could be used by DOTs or private partners to amplify seed. The use of ecoregional seed improves establishment success and is more beneficial to pollinators.

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Final Thoughts

All of the individuals we spoke with are passionate about their jobs and about the value of roadsides in the landscape. They have an interest in pollinators and in managing roadsides with pollinators in mind, but require certain tools to implement positive changes. These last two quotes highlight the key findings from our interviews:

“Growing native plants on roadsides needs to be routine.”
-- Carmelita Nelson, Minnesota Department of Natural Resources

“Roadsides have historically been managed as a utility rather than as a natural resource. We maintained roadsides to keep nature from encroaching, thinking that roadsides are incompatible with functioning habitat and corridors for wildlife. But we know now that it can be done.”
-- Jeff Castor, Florida Department of Transportation

Appendix A - Survey Questions Distributed to the State Department of Transportation Personnel Interviewed for this Project

General policies and procedures for right-of-way (ROW) management
1. Is an integrated roadside vegetation management program (IRVM) used in your transportation agency?

If the answer is yes:
1a. Is the IRVM program mandated by policy?
1b. Is there an organized training program to support IRVM?
1c. Is roadside vegetation management site-specific? (i.e., are different management techniques used in different areas to address site-specific problems?)
1d. Has your agency developed best management practices for your IRVM program?

If the answer is no:
1a. Has your agency developed best management practices for roadside vegetation management?
1b. Has there been any discussion or actions taken towards the development of an IRVM program?

2. What roadside management tools does your agency use most? Please rank the following roadside management tools in order from most used to least, and estimate the percent of ROW that the tools are practiced on:

____ Mowing: ___%
____ Herbicide use: ___%

____ Grazing: _____%
____ Fire: _____%
____ Hand cutting or removal of brush: ___%
____ Biological control: ___%

____ Native vegetation: ___%
____ Other: ____%

3. In areas where mowing may be required are the entire roadside ROW mowed (as opposed to regular mowing of the shoulder and/or intersection for visibility)?
If the answer is yes:
3a. How often does mowing take place and when does mowing take place during the year?
3b. Do you have any existing mowing exceptions to protect sensitive native plants or to avoid spreading invasive species?

4. How frequently are herbicides used, and under what circumstances are they used?
4a. Are broad-spectrum herbicides typically used?
4b. Are herbicides primarily applied through using a boom, by aerial spraying or via spot treatment?
4c. Are applications timed for optimal control of specific target weeds?

5. Do you ever use insecticides as part of your roadside management program?

6. Are there any chemicals used for road maintenance (e.g., road salts) used by your agency that could harm pollinators?

7. What is the average cost of maintenance per acre of roadside in your state?
7a. Do you calculate cost per method? If so, please estimate the average costs for the methods below.
Mowing: ___
Herbicide use: ___

Grazing: _____
Fire: _____
Hand cutting or removal of brush: ___
Biological control: ___

Native vegetation: ___
Other: ____

8. When revegetating a roadside, is it a priority to use native plant species rather than introduced plant species?
If the answer is yes:
What percentage of new roadside plantings incorporate native plant species?
If the answer is no:
Would your agency consider increasing the use of native plant material in roadside revegetations? Why or why not?

9. Is grazing used by your agency? If so, how often, on average, are roadsides grazed during a year, and in what season/s does the grazing typically occur?
If grazing is used:
9a. What species of grazer are you using for roadside grazing?
9b. Is grazing used for invasive plant control, and if so, which invasive species?

10. Is prescribed burning used by your agency? If so, how often, on average, are roadsides burned during a year, and in what season/s are burn/s undertaken?
If burning is used:
10a. As part of your burning procedures, what method do you use to contain a fire?
10b. If your agency uses a fire break, what is the average size of the fire break?

Current management practices that can benefit pollinators
11. Does your agency make any adjustments to manage roadsides for pollinators in general?

12. Does your agency adjust management practices to avoid impacting imperiled invertebrate species (listed or unlisted species) such as the monarch butterfly, the Karner blue butterfly, or the rusty patched bumble bee?

Opportunities and constraints for pollinator-specific roadside management practices
13. Are you aware of any state or local laws that mandate pollinator habitat protection? If so, please elaborate.

14. Reducing the frequency of mowing per year is generally beneficial for invertebrate pollinators. Would it be practical for your agency to consider limiting mowing to one to two cuts per year? Why or why not?

15. If your agency were to mow only once or twice per year, what time of the year would the mowing take place and why?

16. If your agency already has a reduced mowing policy (e.g., a policy to delay mowing to accommodate nesting birds), do you think timing could be adjusted to also benefit pollinators (e.g., delayed until after first frost)?

17. Does your agency currently offer training on native and invasive plant identification alongside herbicide application training?

18. If prescribed fire is a tool you or your agency uses, would you/your agency consider the use of rotational burning on portions of roadsides, leaving unburned refuges?

19. If grazing is a tool used by you or your agency to manage roadside vegetation, would you/your agency consider implementing the following grazing practices: limiting the stocking density of grazers, leaving long rest periods, and timing grazing to avoid damage to imperiled pollinators? Why or why not?

Increasing the value of new roadside plantings to pollinators: opportunities and constraints
20. If native wildflowers are currently included in new seed mixes, do the mixes contain species that overlap in bloom time so that there are floral resources available to pollinators throughout the growing season?

21. In addition to native wildflowers, there are many native flowering shrubs that support pollinators. How frequently are native flowering shrubs planted or included in the seed mix in ROWs?
21a. If flowering shrubs are included in new plantings, how are motorist safety concerns addressed?

22. What percentage or proportion of grasses are typically used in seed mixes for new roadside seed mixes, compared to wildflowers?

23. Are regionally sourced native plant materials readily available to your DOT?

If the answer is no:
23a. If seeds of native plants are limited in your state or region, what steps might be taken to increase availability?
23b. Do you think working with private nurseries and volunteers to obtain locally sourced seeds has potential in your state?

24. Is the cost of native plant material an obstacle at your DOT?

General questions
25. What roadside management changes do you think will benefit pollinators the most?

26. What do you see as potential limitations to implementing pollinator-friendly management practices on roadsides?

27. Do you think that pollinator conservation measures along roadsides are compatible with driver safety? If not, what steps could be taken to improve driver safety?

28. What types of training do you believe might be useful for roadside managers to aid in the implementation of pollinator-friendly roadside management?

29. If there are studies or documents that you consider to be useful guides or BMPs for IRVM programs, please identify them for us.

30. If you are aware of case studies or examples of successful roadside vegetation management approaches that benefit pollinators, please describe them for us.

31. Is there any additional information that relates to roadside management for pollinators that you would like to share with us?

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Appendix B - Survey Questions Distributed to Roadside Restoration Experts Interviewed for this Project

1. What roadside management changes do you think will benefit pollinators the most?

2. What do you see as potential benefits to implementing pollinator-friendly management practices on roadsides?

3. What do you see as potential limitations to implementing pollinator-friendly management practices on roadsides?

4. How might the limitations you describe be overcome?

5. Are there agency partnerships, either state or federal, that would increase the success of pollinator friendly roadside management efforts?

6. In your opinion, does your state transportation agency currently have an interest in protecting pollinators by increasing the habitat quality of roadsides for pollinators?

If the answer is yes:
What measures are you aware of that your state transportation agency has taken, or is planning on taking, to increase the value of roadside habitat for pollinators?

If the answer is no:
6a. What would it take to increase their interest and encourage them to implement changes?

6b. Please rank the following from 1-4 (1 highest, 4 lowest) in terms of information that you believe would be most likely to encourage implementation of pollinator-friendly practices:
_____ Evidence of the value of roadside habitat to pollinators
_____Evidence of the value of pollinators to agriculture,
_____Evidence of the value of pollinators to ecosystem health
_____Evidence of the economic value of pollinator-friendly roadside management

7. Do you think the general public would support pollinator friendly roadside management (e.g., roadside plantings that take several years to establish; reduced mowing/turfgrass appearance)? Why or why not?

8. What types of training do you see as beneficial to roadside managers or transportation agency staff to aid in the implementation of pollinator-friendly roadside management?

9. Please rank the following management strategies that can benefit pollinators according to feasibility (in your opinion) of implementation in your state, and include a brief explanation about your selection.



High / Medium / Low

Limiting mowing (one to two cuts per growing season)

High / Medium / Low

Spot herbicide treatment

High / Medium / Low

Plant identification training for roadside managers

High / Medium / Low

Increased communication with local experts about imperiled pollinators and their habitat needs

High / Medium / Low

Rotational prescribed fire, with refuges

High / Medium / Low

Limited, site-specific grazing

High / Medium / Low

Increased use of native plants

High / Medium / Low

Increased density of wildflowers in seed mixes

High / Medium / Low

Signage indicating pollinator-friendly roadsides (or other public education efforts)

High / Medium / Low


10. Do you think that the use of native plant material in roadside revegetations can be increased in your state? Why or why not?

11. Are regionally sourced native plant materials available to your state transportation agency? Is the cost of native plant material an obstacle?

12. If seeds of native plants are limited in your state or region, what steps might be taken to increase availability?

13. Do you think that pollinator conservation measures along roadsides are compatible with driver safety?

If the answer is yes:
Do you think that there is a perception that reduced mowing of entire ROWs leads to a decrease in driver safety?
If the answer is no:
What steps could be taken to improve driver safety while also improving roadside habitat for pollinators?

14. Are there studies or documents that you consider to be useful guides or BMPs for integrated roadside vegetation management programs? If so, please identify them for us.

15. Have you been involved with, or are aware of case studies or examples of successful roadside vegetation management approaches that protect pollinators? If so, please describe them for us.

16. Do you think there are opportunities within your state to improve roadside habitat for pollinators? If so, please describe these opportunities.

17. Do you think there are opportunities on a national level to improve roadside habitat for pollinators? If so, please describe these opportunities.

18. Is there any additional information that relates to roadside management for pollinators that you would like to share with us?

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Appendix C - State Department of Transportation Staff Interviewed for this Project

State DOT

Interview Participants



E. LeRoy Brady

Manager/Chief Landscape Architect

Justin White

Roadsides Resources Manager


Jack Broadbent

Division of Design, HQ Landscape Architecture Program

Christopher Jannusch

Biologist, Associate Environmental Planner

Kenneth Murray

Senior Landscape Architect


Jeff Caster

State Transportation Landscape Architect

Ashley Binder

Landscape Architect


Cathy Ford

Roadside Program Administrator


Mark Masteller

Chief Landscape Architect, Office of Design

Troy Siefert

Living Roadway Trust Fund Coordinator, IRVM Program Coordinator

Joy Williams

Agronomist, Office of Design


Dianne Kahal-Berman

District 9 Project Manager

Scott Lucas

Head of Operations Maintenance


Michael Shippey

Landscape Architect, Statewide Roadside Development and Botany Program Coordinator


Ken Graeve

Roadside Vegetation Management Unit

Tina Markeson

Roadside Vegetation Management Unit Supervisor

New York

Peter Dunleavy

Associate Landscape Architect

John Rowen

Vegetation and Environmental Program Manager for Office of Transportation Maintenance

Kyle Williams

Operations Environmental Coordinator

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Appendix D - Roadside Restoration Experts Interviewed for this Project



Kelly Evans

Botanist, United States Forest Service

Bonnie Harper-Lore

Retired, Restoration Ecologist, Federal Highway Administration

Dr. Laura Jackson

Director, Tallgrass Prairie Center, Professor of Biology at University of Northern Iowa

Carmelita Nelson

Former Roadsides for Wildlife Coordinator, Minnesota Department of Natural Resources

Dr. Jeff Norcini

Extension Specialist, University of Florida; Ecological and Horticultural Consultant

Scott Riley

Botanist and Regional Restoration Specialist, United States Forest Service

David Steinfeld

Retired, Revegetation Specialist, United States Forest Service

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