University Ecologists Studying Idaho’s Roadside Vegetation

Ecologists at Idaho State University are working with the Idaho Transportation Department to turn state roadsides into veritable “Swiss army knives” of vegetation so they are both more fire-resistant and more welcoming to pollinating insects.

[Above photo by Idaho State University]

Joshua Grinath, assistant professor of community and global change ecology at the school, and his students recently wrapped up the first growing season at three experimental sites along I-15 in Eastern Idaho.

They are working with three different types of ecosystems at those sites, figuring out how to make the land more hospitable to native plants and less so for invasive weeds. That research also includes increasing the habitat’s fire resistance, while becoming a more attractive habitat for pollinators like bees and butterflies.

[Editor’s note: In a July 2021 episode of the Environmental Technical Assistance Program or ETAP Podcast, Matthew Quirey – a  landscape design and research fellow with The Ray – explained how roadside landscapes, more often termed the “right-of-way,” are now being viewed as “habitat assets” instead of maintenance burdens among state departments of transportation.]

Grinath’s research team is testing how different combinations of mowing, herbicide treatments, and seed applications can improve native plant survival in those roadside locales.

This research received its primary funding via a grant from the Idaho Transportation Department, with additional funds supplied by ISU’s College of Science and Engineering, as well as the school’s Office for Research.

In September, the team received additional funding to test how adding certain types of bacteria, fungi, and micronutrients to the soil may improve restoration.

“Roadside management is most commonly focused on a single issue, such as erosion control, but other challenges may be able to be addressed simultaneously,” Grinath explained in a blog post. “Considering these issues simultaneously will help Idaho Transportation Department save taxpayers money and address urgent land management concerns.”

‘Canopy Clearing’ Helping Improve Roadway Safety

Since November, maintenance crews with the West Virginia Division of Highways – part of the West Virginia Department of Transportation – have cleared more than 170 acres of trees and branches overhanging more than 500 miles of state roadways: enough trees and branches to fill up about 170 football fields.

[Above photo by the West Virginia DOT]

Called “canopy clearing,” that process is critical to improving roadway safety. According to the “Vegetation Control for Safety” manual published by the Federal Highway Safety Administration, trees growing close to a roadway can present a “fixed object hazard” to travelers, including motorists, bicyclists, and others. Grass, weeds, brush, and tree limbs can also obscure or limit views of traffic control devices –such as signs or stoplights –as well as approaching vehicles, wildlife and livestock, pedestrians, and bicycles. Thus, controlling vegetation helps reduce crashes and injuries, FHWA noted.

“Canopy clearing” adds another element for improving roadway safety, the agency noted. When trees and shrubs – particularly evergreens – in the right-of-way cast shadows on the pavement, freeze-thaw cycles may create isolated ice patches on the pavement – easily causing loss-of-control crashes. Thus “canopy clearing” or “daylighting” by cutting taller vegetation lets the sun help with thawing and ice control, while also generally helping preserve pavements by preventing the buildup of moisture on roadways during warmer months.

In the past, the West Virginia Division of Highways noted in a statement it could only remove 140 acres of the canopy a year, or 14 acres for each of the state’s 10 highway districts. However, the state lifted that restriction in 2022, allowing districts to cut more trees in between winter snows.

The agency added that, by law, its crews can only clear canopy between November 15 and March 31; a restriction designed to protect endangered bat populations, which do not typically use trees during that time span.

State departments of transportation are also working to expand their knowledge base regarding the impact of trees and shrubbery on roadway safety and pavement longevity.

For example, a 95-page research paper compiled for the Ohio Department of Transportation five years ago by Ohio University suggested designs for a “decision-making tool or process” to assist the agency with tree canopy maintenance practices, assessing the impact of trees and tree species on pavement degradation, road condition, and road safety in climatic conditions typical of Ohio.

KYTC Prepares to do Battle with ‘Noxious Weeds’

The Kentucky Transportation Cabinet is gearing up to control the growth of noxious and nuisance weeds along roadsides throughout the state starting in April.

[Above photo by the KYTC]

KYTC is targeting targets 11 noxious weeds with this effort: Johnson grass, giant foxtail, Canada thistle, nodding thistle, common teasel, multiflora rose, Amur honeysuckle, poison hemlock, marestail, Japanese knotweed, and kudzu.

KYTC added that local property owners may file a request that highway crews treat select nuisance weeds found on adjacent state-owned rights of way as well. To request weed treatment request submit a written application to the local KYTC highway district office, the agency added.

“Weeds are more than a nuisance-they pose safety concerns,” explained KYTC Secretary Jim Gray in a statement.

“Actively treating the weeds on state-maintained property enhances driver visibility near roadways, prevents damage to ditches and drains, and minimizes the presence of plants that attract deer near highways,” he said.

Noxious weeds often invade and destroy the roadside turf grass, leaving those areas vulnerable to erosion, KYTC added. They can also smother native plants through rapid reproduction and long-term persistence.

Twenty years ago, the Federal Highway Administration published a compendium of resources aimed at removing invasive species of plants that might take root along roadways nationwide. They can cause “significant changes” to local ecosystems, upsetting ecological balances and causing economic harm to the country’s agricultural and recreational sectors.

Connecticut DOT Helping Battle Spotted Lanternfly Invasion

The Connecticut Department of Transportation is working with the U.S. Department of Agriculture, the Connecticut Agricultural Experiment Station, and the Connecticut Department of Energy and Environmental Protection to battle an invasion of the “spotted lanternfly,” which could severely affect the state’s agricultural crops – particularly apples, grapes, and hops, and ornamental trees.

[Above photo via Wikimedia Commons]

The spotted lanternfly – formally known as Lycorma delicatul – is not actually a fly, but an exotic and invasive sap-feeding planthopper that feeds on more than 70 species of plants. The preferred “host” of the spotted lanternfly is a plant known as “tree-of-heaven” or “Ailanthus altissima,” which itself is highly invasive and abundant along highways, in urban areas, and along the edges of agricultural and industrial areas.

The agency said in a statement that the concern is that the feeding of spotted lanternfly nymphs and adults on sap from trees and vines weakens the entire plant, while the excretions from these leaf-hopping insects encourage the growth of black sooty mold, thereby reducing photosynthesis.

As a result, agricultural crops face reduced yields due to the lanternfly’s feeding on fruit and general weakening of plants, if not destroying them outright.

To help combat the spread of this invasive species, the Connecticut DOT is spreading the word via informational posters and flyers at its rest stops about the spotted lanternfly invasion and is helping place traps in highway right-of-ways to help gauge the spread of this invasive pest. The agency added that it is training Connecticut field personnel in identification, reporting, and proper precautions to halt the spread of the lanternfly.

The agency also noted that during the months of August through November the adults of this pest can attach themselves or “hitchhike” on vehicles and trailers, so it is asking travelers to check their vehicles the lanternfly, and – if found – to take a picture, destroy the insect, and report it to The Connecticut Agricultural Experiment Station.

State departments of transportation across the country are regularly engaged in a variety of efforts to beat back invasive insect and plant species.

For example, Kentucky Transportation Cabinet highway crews engage in an annual effort – usually at the beginning of March – to control the spread of invasive plant species that can damage transportation infrastructure as well as interfere with motorist “line-of-sight.”

Such efforts sometimes involve usual tactics, as well. For instance, the California Department of Transportation launched a pilot project in February 2020 that used 300 goats for nearly a month to help remove invasive non-native weeds such as bur clover, mustard, and thistle from a 20-acre site adjacent to Highway 1 just north of the Piedras Blancas Lighthouse. Instead of relying on herbicides, Caltrans said the goal of this project is to deploy a “more sustainable approach” to revitalizing the native coastal prairie adjacent to a highway realignment project originally completed in 2017.

KYTC Treating for ‘Noxious Weeds’ Along State Roadways

Kentucky Transportation Cabinet crews began treating for noxious and nuisance weeds along state roadways in March, with those treatments designed to help control the spread of “undesirable plants” along state highway rights of way to improve driver safety and ensure efficient maintenance operations.

[Photo by the KYTC.]

In particular, KYTC crews are targeting Johnson grass, giant foxtail, Canada thistle, nodding thistle, common teasel, multiflora rose, Amur honeysuckle, poison hemlock, marestail, Japanese knotweed and kudzu.

The agency added that those noxious weeds often invade and destroy the roadside turf grass, leaving these areas vulnerable to erosion. They can also smother native plants through rapid reproduction and long-term persistence.

“Left uncontrolled, noxious weeds can grow so large that they interfere with a driver’s line of vision on highways,” Jim Gray, explained Jim Gray, KYTC secretary, in a statement.

“Weed maintenance is important in preventing potential damage to pavement and embankments, as well as clogged ditches and drainage problems,” he said.

State departments of transportation are also experimenting with other forms of weed control as well.

For example, the California Department of Transportation – known as Caltrans – began using goats in early 2020 as part of a pilot project to control weeds within a 20-acre site adjacent to Highway 1 just north of the Piedras Blancas Lighthouse.

Instead of relying on herbicides, Caltrans is taking what it calls a “more sustainable approach” to revitalizing the native coastal prairie adjacent to a highway realignment project originally completed in 2017.

According to an agency statement, the project brought in 300 goats for nearly a month to help remove invasive non-native weeds such as bur clover, mustard, and thistle.

Arizona DOT Works to Protect Plant Species in Highway Construction Zone

As an 11-mile reconstruction project along Interstate 10 between Interstate 17 and the Loop 202 gets ready to start, biologists with the Arizona Department of Transportation are preparing to relocate native plants out of the way.

[Photo courtesy of the Arizona Department of Transportation.]

The agency said its crews are identifying state-protected plants in the planned construction zone – such as ocotillo and saguaro and barrel cactus – and studying roughly 2,500 trees to identify native species, including palo verde, mesquite and ironwood.  

The Arizona DOT plans to relocate most of them into temporary nurseries during construction, transplanting them back to their roadside habitats when construction work is complete. 

“Protecting the natural Arizona environment is an important part of our work,” said Robert Samour, senior deputy state engineer and leader of Arizona DOT’s major projects group, in a statement.

Photo courtesy of the Arizona DOT

“There were more than 1,000 plants along the South Mountain Freeway that we maintained for more than three years and replanted after construction to preserve the plants and the beautiful landscape,” he said. 

[The Arizona DOT conducted a similar relocation effort in 2018 for native cactus plants located near a bridge replacement project on U.S. 60 where that highway crosses Pinto Creek six miles from the town of Miami, which is a little more than 81 miles due west of Phoenix.] 

The Arizona DOT anticipates starting the I-10 reconstruction project this summer, relocating native plants and utility lines. The agency anticipates construction will be complete by late 2024, with the project ultimately improving travel time and safety, as well as easing access to Phoenix Sky Harbor International Airport and supporting local, regional, and state economic growth. 

Video: Caltrans Using Special Saws for Safer Tree Removal

The California Department of Transportation and its contractors are deploying a new tool to safely speed up the removal of dead, dying, and diseased trees throughout the state: Telescoping grappling saws.

[Photo courtesy of the California Department of Transportation.]

The agency said in a statement that such saws allow its crews and contractors to take trees down at a faster pace than traditional tree removal processes; completing that process with greater safety from the ground via remote control, well outside the fall zone for trees being removed.

Ohio DOT Plant Relocations: Rare, Yet Necessary

Relocating a drove of rare plants from an environmentally sensitive transportation construction site is a meticulous operation – and often state departments of transportation are running the show.

[Photos courtesy of Ohio DOT]

Take Ohio, for example, home to 400 species of rare plants accompanied by a spate of state laws designed to protect rare, endangered species at certain hotspots, like one in the Oak Openings Region of Toledo – an area known for its sandy soil, where only certain varieties of rare plant life thrive.

So when transportation construction beckons in such locations, biologists within the Ohio Department of Transportation suit up for action.

“The Ohio Department of Natural Resources (ODNR) tells us where to move the rare species,” said Matt Raymond, ecological program manager for the Ohio DOT, who stressed that the federal National Environmental Policy Act as well as state laws help guide such plant relocation endeavors.

The agency started the relocation at the Oak Openings site by excavating the plants, which included Bowles’ golden sedge (Carex aurea), Baltic Rush (Juncus balticus), hairy pinweed (Lechea villosa), Scaly blazing star (Liatris squarrosa), prairie thimbleweed (Anemone cylindrica) and wild lupine (Lupinus perennis).

“We moved them to a park that’s located several miles from of the excavation and then helped get them planted,” Raymond said.

Given the delicacy of such operations, he explained that intermittent follow-up on the progress of the plants in their new home occurs at various intervals.

“Just how many plants are moved depends on what’s growing on the site,” Raymond noted. For instance, he pointed to the 2014 Portsmouth Bypass project, a 16-mile, four-lane highway that built to connect U.S. 52 near Wheelersburg to U.S. 23, just north of Lucasville. That job called for the removal of 150 Southern Monkshood (Aconitum uncinatum) and 800 Primrose-leaved Violet (Viola primulifolia) to nature preserves.

“So we moved 950 endangered plants,” said Raymond. “We sent our biologists to oversee the excavation, because the crew needed direction as to what to look for and where to dig. We also received help from ODNR employees of the preserves that receive the plants, too.”

Lastly, Raymond offered the example from 2012, where ODOT relocated the threatened Drummond’s aster (Symphyotrichum drummondii) from the construction limits of a federally sponsored bike/towpath project along the historic Ohio and Erie Canal, in Stark and Tuscarawas counties. During the ecological survey, the agency’s team also documented in detail about 500 of the plants living throughout the project area before relocating them elsewhere along the towpath site.

Relocating sensitive plants is only been required in Ohio “every three or four years,” Raymond explained said, “but it’s easy to know when it’s the right move to make. It’s basically the same thing we’ve done in other efforts with ODNR to support the environment with various animals and insects, like the Monarch Butterfly, the bee population, animals, etc.”

It all comes down to common sense and having the laws in place to take appropriate action, he pointed out.

“Right-of-ways are typically not the best places for plants, due to road salts, [vehicle] exhaust, mowing, and other disruptive activity,” Raymond emphasized. “So we re-plant in areas where new pollinator programs reduce the frequency of mowing and heighten the effectiveness of the native habitat.”

Other state DOTs are also engaged in similar efforts.

For example, biologists from the Arizona Department of Transportation conducted a multi-day mission in 2018 to protect native hedgehog cactus from a bridge replacement project on U.S. 60 – carefully relocating them to local greenhouses for two-year stay well away from the bridge construction site.

The biology team at the California Department of Transportation also performs another key duty: overseeing the removal of invasive plant species, ones that that threaten California’s sensitive natural areas and complete with native plants. To do that, Caltrans coordinates with various state and federal agencies including the California Invasive Plant Council, the California Department of Food and Agriculture, and the U. S. Department of Agriculture.

At the Texas Department of Transportation, another key role performed by its biologists is the planting and nurturing of more than 5,000 species of wildflowers along with native grasses that flourish along the state’s roadsides. “TxDOT’s wildflower program not only helps our highways look good but also reduces the cost of maintenance and labor by encouraging the growth of native species that need less mowing and care,” the agency noted.

Maine DOT Shares Insight into Roadside Vegetation Management Program

The Maine Department of Transportation recently provided a behind-the-scenes look at its ongoing efforts to control brush along selected state roads via an “integrated” strategy that marries the use of herbicides with mowing and the hand-removal of young saplings growing too close to the pavement.

“Roadside trees are much easier to control when they are small,” the agency said in a statement. “Trees allowed to grow close to roads prevent proper water drainage and may obscure drivers’ views of large animals such as moose and deer. Controlling roadside vegetation is a key safety and road maintenance activity requiring yearly effort.”

In various locations, the Maine DOT noted it may also extend its vegetation control efforts to areas surrounding guardrails. “Reducing vegetation near guardrails increases safety because it protects our workers from tripping hazards and ticks,” the department pointed out. “Guardrails free of vegetation also function properly and are easier to maintain.”

Photo by Maine DOT

Integrated roadside vegetation management or IRVM is a strategy with a long history within the state DOT community, dating back to the 1970s. Iowa, for example, was one of the first states to establish IRVM programs at the city, county, and state levels with a goal of providing an alternative to “conventional” procedures that relied on the extensive use of mowing and herbicides, which provided often too costly to implement on a regular basis and increased the potential for surface water contamination.

That’s why in Maine DOT’s case, all herbicide treatments for brush, weeds, or invasive plants are selected to minimize impact to surrounding vegetation – deployed at the lowest application rates to protect workers and the environment.

[Selecting the correct herbicide is critical; a lesson the Oregon Department of Transportation learned the hard way as it just wrapped up a five-year effort to remove 2,300 Ponderosa pine trees poisoned by the use of herbicide aminocyclopyrachlor – also known as Perspective – sprayed along a 12-mile stretch of U.S. 20 to kill vegetation that posed a fire hazard.]

Starting in 2004, the department also began an “every-other-year” herbicide application program to help further reduce use of such chemicals, while encouraging municipalities and private citizens living adjacent to state roads to enter into a Cooperative Vegetation Management agreement if they are concerned about herbicide use.

Such agreements outline the municipal or landowner responsibilities for maintaining roadside vegetation; because when roadsides are properly maintained under such pacts, there is no need to use herbicides, the Maine DOT said.

Pine Tree Poisoning Provides Lessons for Oregon DOT

The Oregon Department of Transportation is approaching the end of a multi-year environmental and public relations ordeal in which a seemingly routine herbicide-spraying project in a national forest poisoned 2,300 towering Ponderosa pine trees that eventually had to be cut down.

By June, the agency should be grinding down the last of the stumps left by its massive 2019 logging of herbicide-poisoned trees along U.S. 20 in the Deschutes National Forest in Central Oregon.

Photo courtesy Oregon DOT

Aside from the wood chips, what will remain are valuable environmental lessons the Oregon DOT is taking to heart.

The problem began when the Oregon DOT contracted with Jefferson County Public Works in 2013 to spray the herbicide aminocyclopyrachlor – also known as Perspective – along a 12-mile stretch of U.S. 20 to kill vegetation that could pose a fire hazard.

In 2014, U.S. Forest Service rangers noticed some trees were stressed, but no one linked it to the herbicide until the spraying was completed in 2015. By then, the damage was done and the Oregon DOT determined the trees – some of which were 36 inches in diameter – were safety hazards and had to be removed.

Environmental groups and residents criticized the agency, its contractor and the U.S. Forest Service for using the herbicide. Although a review of the decision-making process did not fully put the blame on the Oregon DOT, “at best, it wasn’t clear,” explained Joel McCarroll, Oregon DOT’s District 10 manager.

“We took full responsibility. It was not a comfortable decision, but I felt it was an easy decision,” he emphasized. “It just didn’t make sense to lay the blame off on someone else. It was just easier to go forward and get this done.”

Photo courtesy Oregon DOT

To that end, the agency held open houses for public discussion of its remediation plan because “we needed to be transparent with the public – we had more than 2,000 trees that had to come down,” McCarroll noted. “We were very clear about the criteria and the process we were using. And, people were fine. I’ve had people come unglued on me for other things at public meetings, but these crowds were respectful.”

Although Perspective was legal to use, a warning label about its use around pine trees was added before the project ended, but no one caught the change. “We overlooked a warning label, and that’s one of the process-improvement changes we’ve made,” McCarroll said.

In response to the tree killing, Oregon became the first state to prohibit the use of aminocyclopyrachlor in numerous applications on May 9, including along rights-of-way. Additionally, each Oregon DOT district now has an integrated vegetation program, and personnel within the district are cross trained to prevent a loss of institutional knowledge, McCarroll noted.

“Learn from our experience – you still have to have the expertise internally, even if you’re contracting out spraying,” he explained. “If you’re dealing with highways that are on federal lands, make sure the decision-making is clear. And it’s important to be public about your process.”