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Feature Article Sept/October 2001
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A look at current practices in roadside vegetation management. By Janis Keating Alabama:
Something Old, Something New
When you’re cruising down the interstate, you might notice colorful wildflowers or landscaping at the side of the road. Those beautiful little patches of nature don’t just appear naturally; every state employs hundreds of workers to manage roadside vegetation. Facing concerns over roadside appearance, driver safety, erosion control, and stormwater pollution, state departments of transportation operate a variety of programs to get the job done. In Erosion Control’s April 2000 article, "Integrated Roadside Vegetation Management: A Quick Glance Around the Country," state Department of Transportation (DOT) employees reported on various herbicide, mowing, and integrated weed-control practices. With rising concerns about chemical use, the further implementation of National Pollutant Discharge Elimination System (NPDES) regulations, and the rising cost of gasoline for mowing machines, have state DOTs changed their practices since then? The answers overall: not much, although some changes noted in the April 2000 article are currently under further implementation. One interesting trend: Some state DOTs are implementing biocontrols, using insects to help fight the weeds that bug them. Alabama: Something Old, Something New Ed Phillips, assistant state maintenance engineer and head of the Alabama DOT (ALDOT) Management and Training Section, reports that the state is continuing its wildflower plantings, and Bermuda grass and Bahia grass are still being planted in the appropriate climatic zones. "We’re having mixed success with the wildflowers," Phillips says. "We’re not getting as much as expected in median areas. One problem: some counties considered the crimson clover we planted an invasive weed and killed it!" Undaunted, ALDOT is making greater efforts to plant wildflowers. One candidate, Moss Verbena, is not readily commercially available, so ALDOT is trying to propagate the plant. Alabama is also implementing two new programs. "The governor established the ‘Star City’ program and ‘Gateway to the State’ enhancements," says Phillips. "Gateways are landscaped vegetation projects sited at interstate and state road entrances. We put in and maintain these sites, which include landscape plants and some wildflowers. They’re fairly manpower-intensive, but using drought-tolerant species helps cut down on some maintenance. Star City creates similar projects for our cities; they can get grant money for Star City sites. We’ll install the plantings, but then the cities maintain them." According to Phillips, rising gasoline prices won’t prompt Alabama to reduce mowing, as the state’s mowing practices have already decreased significantly in the few years. "Clear zones are managed," he says. "But past that, we’re letting the ground go fallow."
Mowing chores were once farmed out to contractors, but now because of
strict state guidelines, state crews do the honors. "New construction
is contracted out, but maintenance mowing and herbicide applications
are done by the state. The most important concern is safety; we maintain
the road’s recovery area. Aesthetics is secondary, although important,"
Phillips says, adding that leaving "natural" space in the
right of way is intended to generate a wildlife habitat.
Kudzu is a problem for Alabama, but not as much as for some other states. Cogon grass, Imperata cylindrica, is ALDOT’s biggest worry. This thick, dense grass eliminates any competition and becomes the only ground cover. It’s becoming a problem for Alabama’s timber industry because it chokes out replant seedlings. In addition, wildlife can’t eat it, and it’s susceptible to fire. Phillips notes that Auburn University is investigating cogon grass control. Does his department suffer budget crunches? "Yes, always," says Phillips. "I’d guess our vegetation management activities cost about $20 million yearly, and that includes litter pickup, although we do have an ‘Adopt a Mile’ program. What monies we’ve saved from changing mowing patterns has been shifted into other areas." What about "free" manual labor, as seen in the movie Cool Hand Luke? "There are no more chain-gang grass crews," Phillips laughs. "We do use them in some cases, around facilities, for some litter pickup and woody brush control. But for the most part, the gangs were more trouble than they were worth." Arkansas: Beauty Is As Beauty ... Doesn’t
Thanks to less frequent mowing and more wildflower plantings, motorists in Arkansas are learning a new aesthetic. "People aren’t used to thinking of a natural mixture of grasses and forbs as pretty, but more and more are recognizing it for its beauty," says Phillip Moore, a botanist with the Environmental Division of the Arkansas Highway and Transportation Department. As many states do, Arkansas maintains three distinct roadside zones: a high-maintenance zone adjacent to the roadway; a transition zone that’s less tended; and a woody zone, which extends to the right of way’s border. Medians usually receive "transition zone" care. Much of Arkansas’ mowing–not only near the interstates, but also along its 13,000 mi. of state routes–is contracted out. Moore can’t yet predict whether rising gas prices will have an impact on mowing schedules. "Our medians are mowed three times a year, and we time these mowings to allow wildflowers to take hold. We postpone mowing so crimson clover can seed itself, a practice which also helps Coreopsis tinctoria and C. lanceolata. Our wildflowers also include five different species of Echinacea. In the fall, we do a ‘cleanup’ mowing," he explains. "On slopes we plant native prairie-type grasses, little or big bluestem, or Indian grass. For some sites, around the Buffalo National Park, for example, we’d like to do native revegetation. We’d also like to find some Missouri ecotypes, but they’re not yet available, at least not in the quantity we’d like," Moore adds. Wildflowers are one thing, weeds another. "Johnson grass [Sorghum halepense] is the worst–a bane to agriculture as well," says Moore. "Although Nodding thistle is a problem, we’ve pretty much kept Canada thistle [Cirsium arvense] out of the state. However, we’re starting to have kudzu [Pueraria lobata] problems."
Everything Wants to Live in Florida Whether humans are escaping winter or invasive plants, "Everything wants to live in Florida," says Gary Henry of Florida DOT. Florida DOT (FDOT) doesn’t do widespread herbicide spraying because of the state’s high water table. "We use some contact herbicides, though," says Henry. Mowing is Florida’s main weapon against weeds. The frequency varies across the state; northern areas are mowed nine times a year; southern Florida is mowed twice as much. Vegetation is mowed down to 6 in., and all mowing and replanting is contracted out. Quite a few invasive weeds want to call Florida home. Kudzu, cogon grass, giant reed, and Spanish needle poke their way into much of the state, and southern Florida does battle with Brazilian pepper and Melaleuca. "Melaleuca outside of the right of way is a tremendous problem," Henry says. "University of Florida Gainesville is looking into importing bugs–biological controls–that will attack some of those weeds. "We’re the land of flowers, and we sure want to keep them here," Henry continues. "In our wildflowers program, we put down 20 tons of seed a year, some in our mulching operations. We don’t care if the wildflowers bloom right away, just as long as they root." Some of the seed FDOT puts down includes Gallardia pulchella, black-eyed Susan, Lanceleaf coreopsis, Coreopsis tinctora, and Phlox drummondii. "We try to plant as close to native as we can," Henry notes. "As we sometimes have trouble finding wildflower seed sources, we’re trying to ‘kick-start’ growing seed in the state." The 2000 election did not affect Maryland’s mowing practices; the governor, who likes the trimmed look, remained in office. "We still mow every three to four weeks in spring, a little less in the summer," says Don Cober, a technical resource specialist with the Landscape Operations Division of the State Highway Administration. "About 50% of our mowing is done by contractors. Sometimes in spring we mow every seven to 14 days."
Past the mowed area, however, Maryland is putting in wildflowers and some grasses. "Last fall we put out some mixes; we’re getting some color from them. Dame’s rocket and Shasta daisy bloomed in May; citizens seem to like the color of plants that aren’t native. Depending on the area, wildflowers could be planted within 5 feet of the lane, or up to 30 to 50 feet away. But if the area is not available to the public, we don’t plant it," Cober notes. The University of Maryland and the Natural Resources Conservation Service (NRCS) are developing both a tall (4- to 6-ft.) and a short (about 3-ft.) roadside mix for the state’s use. The mixes consist of mostly native grasses and wildflowers; Cober’s crews will sow some of these mixes this fall. "The tall mix will include switchgrass and Indian grass," Cober says. "For some areas, some fescues do a better job at stopping erosion. They’re better adapted for soil and weather conditions." Other grasses in the Maryland mixes include fescue, Kentucky bluegrass, perennial rye, purple top, bluestem, and big bluestem. Wildflowers include ox-eye sunflower, Heliopsis helianthoides, brown-eyed sunflower, New England aster, spiked gay feather, New York ironweed, blue vervane, beard tongue, joe-pye weed, wild bergamot (Monarda fistulosa L.), and boneset. Despite the mowing and planting, Maryland still has to contend with weeds, and noxious-weed laws are enforced. "Our Department of Agriculture investigates weed complaints," Cober reports. "If a landowner ignores the problem, after a few infractions, they can be taken to court." Cober lumps weeds into two basic categories. "Nuisance weeds are a problem, but not yet out of control, such as phragmites and rose multiflora. Noxious weeds, such as Johnson grass and thistles, are highly invasive and have to be dealt with right away." Each year, Maryland’s enhancement program involves several-hundred-thousand dollars’ worth of landscaping. "We use a lot of native shrubs," Cober says, "including Indian coralberry, Indigo bush, red and black chokeberry, silky dogwood, fragrant smooth and staghorn sumacs, common ninebark, arrow-wood, black haw, and nannyberry viburnum. "Our major responsibility is to deal with the environment," he notes, "to preserve and enhance Maryland’s roadsides. Through wetland creation and protection we get involved in stormwater management. We’re also involved with erosion and sediment control, stream restoration, wildlife protection, and restoration. We also get involved in historic preservation and the highway sound-barriers program, and in partnership with civic groups we work with the Streetscapes program, revitalizing area streets. Our mission is to provide customers with a safe and well-maintained, attractive highway system that offers mobility and supports Maryland communities, the economy, and the environment." He adds, "We’re on a statewide crusade to keep roads clean, safe, and litter-free, so we also have a recycling program for all the stuff we pick up: tires, batteries, motor oil, et cetera." Michigan: No-Mow Is for the Birds
Darwin Heme, a resource analyst for Michigan DOT, reports that the state is still mowing a 12-ft. strip along most roadsides. "We do some brush control past the strip, but not much. It’s part of our reduced mowing program, which saves money and creates more habitat for nesting birds." Michigan’s mowing program is designed for the safety of motorists and animals. "With that mowed strip, drivers should be able to see animals when they come out of the brush, before they dart out into the road," Heme says. Mowing frequency depends on the area. The Upper Peninsula is mowed once per season, the north Lower Peninsula might get two mowings, and its southern area might get three. "We try to cut them before Memorial Day and then sometime in the summer," Heme adds, "although there’s talk of eliminating one mowing because of budget overruns from this past winter’s snow removal." Currently, medians are mowed depending on their width. "If they’re 70 feet wide or less, we mow it all," Heme says. "More than 70 feet, we mow 12 feet on each side. However, in 2002 that ‘full-mow’ guideline will change to ‘if 50 feet or less.’" Unmowed medians, especially those containing tall, hard-to-kill weeds such as phragmites, can cause problems for lead-footed drivers. "I’ve seen state troopers hiding in there," Heme chuckles. Although the state isn’t mass-planting native grasses, Heme reports that it plants "a little bit here and there. We have planted some bluestem and some wildflowers. We maintain wildflowers their first three to four years, until they sustain themselves." He notes that the department is trying to use more hardy fescues for lower growth. For other weed controls, Michigan has "a fairly decent—size spray program–about every 18 months–usually only where needed, such as guardrail areas. If there are complaints, we might go in and kill certain noxious weeds, but the state has no formal noxious-weed program," he says. "Our most important goal is safety," Heme says. "But through less mowing we’re trying to create more natural habitats, because what’s out there is what we have in some (urbanized) areas." Montana: Flora’s Roadside Victory
The year 2001 brought a small victory to Montana’s roadsides.
"Now, in reconstruction projects, crews must add topsoil and reseed
up to the pavement," says Phil Johnson of Montana Department of
Transportation’s (MDT) Environmental Services. "Finally,
a commitment to do this! It’s a means of suppressing noxious weeds
on the roadside, and it also helps eliminate erosion. Montana almost exclusively contracts noxious-weed control out to county weed boards. The counties apply for funding, and MDT administers the funds, which are doled out by the state legislature. "Our maintenance crews do very little [weed control] except around guardrails," Johnson says. Texas: Everything’s Better With Bluebonnets on It
Fifteen-foot mow lanes are the norm alongside Texas highways, with one caveat: "We try to coincide mowing with the wildflower season. We mow after the bluebonnets [Texas’ state flower] have set seed," explains Paul Northcutt, former Texas DOT director of vegetation management. (The recently retired Northcutt is now executive director of the National Roadside Vegetation Management Association.) "Each district looks at its roadsides and makes a trimming judgement," Northcutt says, "taking into account the percentage of urbanization. Urban areas get a trimmer look. As mowing is a ‘money issue,’ often the first question asked is, ‘Is this an area I need to mow at all?’" Usually roadsides are mowed to the minimum "safe" amount; the "recovery lane" adjacent to the pavement is mowed most often. Full-width mowing is done no more than twice a year. More than 95% of mowing is contracted out, and the full cost of 2000’s statewide roadside management reached $45 million. "Almost 2 million acres are being mowed," Northcutt points out. Because of the state’s vast size, Texas’ weed problems vary with its soil/climate zones. "In west Texas, there are more problems with brush species in the right of way," Northcutt reports. "East Texas has more problems with herbaceous plants. We design and manufacture our own spraying equipment, and 99% of our spraying is done by state crews." Even before NDPES guidelines, Texas DOT was careful with chemicals. "We use a narrow list of chemicals," Northcutt explains. "We won’t even look at ones that volatize, are restricted, or that are known to harm water. Around Austin, within aquifer zones, we tailor spraying. We do our own herbicide research in test plots for two to three years before we’ll use them in the field." Texas does not have a noxious-weed law, but noxious-weed control districts exist within the state. Johnson grass, the bane of many a state DOT, is sometimes used for cattle forage in Texas, but the persistent, invasive weed is still not welcome on roadsides. "When the end of the world comes, there’ll be two things left alive on earth," Northcutt jokes. "Cockroaches and Johnson grass." Even with 7,000 mi. of roadsides to manage, Wyoming’s job is a little easier than in some other states. "Most of Wyoming is high desert," says John Samson, state agronomist. "Our average rainfall is only 10 to 12 inches, so growth is not a huge problem." Wind erosion is the main worry. "We’re using vegetation, native species, with low-to-moderate growth to control erosion. In some areas we use commercial erosion blankets because they don’t require maintenance, and they last two to three growing seasons out here," Samson reports. Nearly 100% of Wyoming’s roadside management is done by state workers. Samson expresses concern that rising costs, Wyoming’s fairly low tax rate, and the rising cost of gas will hurt roadside management budgets, even though the programs are not extensive. "For weed control, we mow to 6 inches about once a year on road shoulders but not ditch bottoms or slopes," Samson explains. "In urban corridors we mow twice or even four times a year, depending on what the public wants. We do some spot treatment with herbicides–spotted knapweed is our worst weed–and sometimes, because we go through a national forest, we hand-pull weeds." Wyoming is especially careful to keep herbicides out of the water table. "Seven of the West’s major headwaters are here," Samson says proudly.
Herbicide use becomes more regulated each year, and even reduced mowing programs are increasing in price; what can states do to fight weed problems? Some are looking toward biocontrol, the process of using plant diseases or plant-eating insects to combat weeds. In Stillwater County, MT, Weed District Supervisor Wayne Pearson has been "bugging weeds" for nearly 20 years. "Obera, the horned beetle we used to combat leafy spurge [Euphorbia esula], comes from Europe, where leafy spurge originates. In 1983, I was able to get a bottle of them, about 80 insects, and I released them in a field. It’s a slow process. It takes a long time for them to do the job, but now they’re established pretty well here in the county," he says. About a dozen years ago, the local Columbus High School became interested in the project, and Pearson’s department made a deal with the classes to collect insects. "They collect bugs from the areas where we’ve established them, then we transport the bugs to another area with a spurge problem. It’s actually the beetle’s larvae that eat the spurge’s 20-foot taproot, which effectively kills the plant," he explains. "In parts of the county, we’ve eliminated leafy spurge with the beetles’ help." Three to five years after release, one can start to see the damage the beetles are doing to the weeds. "Sometimes we can see damage after the second year," Pearson says. "Once the beetles are established, we get nearly 100% results. July’s their prime reproduction period. They lay eggs in the plants’ stems, then the larvae get down into the roots and overwinter." Thus far, he hasn’t observed the beetles discovering another host plant they like. Pearson offers a brief overview of the process of introducing a helpful insect into the United States. "The International Institute of Biological Control in Switzerland has to approve it. They test them first to make sure that the bugs will only eat one host plant and also that the bugs won’t bring any sort of disease into the country. ARS, the Agricultural Research Services of the US Department of Agriculture [USDA], and the Animal and Plant Health Inspection Service lead the project in this country, and because the problem occurs north of here, we cooperate with Canada on this sort of project. It takes about $400,000 per species, and about seven years, to get insects cleared for importation." Other insects, flea beetles, also work on the spurge problem. "We use the same method of capture and re-release," Pearson says. "We use Nigrescutis, Aphthona flava, and A. cyprisia. The Bureau of Land Management and the Forest Service contribute money to this program, and also send kids out to collect the bugs. Now there’s even a company in Bozeman that sells the beetles." Of course, with bugs hard at work, Montana restricts insecticides in those areas. "We’re also working on bugs to combat Canada thistle and hound’s-tongue, and we have some that work on spotted knapweed. Don’t kill our bugs!" Pearson concludes. More details on ARS’ "buggy" endeavors are available on the Web at www.ars.usda.gov/is/AR/archive/mar00/weed0300.htm.
"We haven’t really done much biocontrol," says Michigan’s Darwin Heme. "Michigan State has done some studies for purple loosestrife, but we haven’t done any large-scale work yet." "Not much biocontrol of weeds here," Texas’ Paul Northcutt agrees. "We’ve used the musk thistle beetle a little. But we’re beginning to look at biocontrols for fire ants." The search for a bug that will eat Canada thistle is underway in Maryland. The weed still covers the state, despite attempts to control it using various insects: Cassida rubiginosa, Ceutorhynchus litura, Cleonis piger, Rhinocyllus conicus, Urophora cardui, and Larinus planus. "We’re trying to find where the plant originated, and we’re working with University of Maryland, the USDA, and the Center for Investigation in Sweden, trying to send a team into Russia where Canada thistle originated, to find the pests that eat the plant," Don Cober reports. He’s hoping the future will bring an integrated weed-control program, a combination of mechanical, chemical, and biological weed control. He adds, "I’d also like to find something that would eat those phragmites!"
Janis Keating is a frequent contributor to horticultural magazines.
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