Integrated Roadside Vegetation Management: A Quick Glance Around the Country

April 1, 2000

Last fall there were two national conferences on roadside vegetation management: the 16th Annual Conference of the National Roadside Vegetation Management Association (NRVMA) in Louisville, KY, and the 2nd Annual Managing Roadsides Naturally Conference hosted by the Lady Bird Johnson Wildflower Center in Austin, TX.

Each conference had a character of its own with distinct differences in focus and audience. In the broadest of terms, the NRVMA event is sponsored by the herbicide industry, attracts state departments of transportation (DOTs) and roadside maintenance supervisors, and is about mowing and spraying. At what seems the opposite end of the spectrum, the Managing Roadsides Naturally Conference attracts wildflower lovers and is not about mowing or spraying.

The two conferences do not represent opposing schools of roadside management philosophy. More accurately, they represent two sides of roadside vegetation management that virtually every state DOT in the country is trying to bring together under one program. Environmental, financial, and aesthetic interests are pushing proponents of more vegetation control and supporters of less vegetation control toward common ground. As DOTs try to satisfy both objectives, roadside management programs are becoming much more integrated.

In 1988, Iowa legislature adopted a program called Integrated Roadside Vegetation Management (IRVM). The program grew out of the Groundwater Protection Act and was aimed at reducing herbicide use in highway rights of way. If agricultural pesticides could wind up in drinking water, so could those used in roadsides. Iowa DOT stopped broadcast spraying and started considering alternative weed control methods. The legislation called for the use of native species in roadside plantings because prairie grasses and wildflowers are the plants best adapted to local conditions and most able to hold their own against weeds. Bridging the gap between the two poles of roadside vegetation management, IRVM gave policymakers an environmentally sound way to provide safe, responsible roadside vegetation management.

Other states adopted similar programs for reducing use of roadside chemicals and mowing and for promoting low-maintenance vegetation. These programs have been in place for a few years, so it is time to look in on how the different states are doing. To assess the status of IRVM nationwide, roadside management personnel were contacted in 14 states around the country.

How Do You Spell IRVM?

The DOT employees were first asked if their states practice IRVM and how they define it. Most of the 14 states indicated that they are familiar with the term IRVM even though most said they do not refer to their own roadside programs by that name. Half of the states said they are practicing IRVM. Several said they have not yet achieved what they would call an “integrated” program. Some feel they are driving toward it.

Following are the definitions of IRVM that were offered. These definitions provide a thorough exploration of the term. A representative for one DOT feels its program is not integrated because IRVM is management by committee and one person dictates all its management practices. The one state not familiar with IRVM called its own program “a comprehensive program of mowing and spraying using different low-maintenance seeding mixes for the state’s three climatic zones.” One state has a sustainable vegetation program, identifying locations that should not be mowed or sprayed or that are candidates for low-maintenance vegetation and reduced management.

Many view IRVM as a weed management term-“what you do to kill weeds” or “a broadcast program using a variety of tools.” One employee believes in IRVM and native plantings as herbicide-reduction programs, stating, “They require patience but will work.” Another says, “I believe in IRVM but do not think of it as a money saver, as in ‘plant this and save on herbicides and mowing.'”

One state that feels it does not have an organized IRVM program defines IRVM as “utilizing the best tools available for a particular situation.” That DOT uses mowing, spraying, handcuffing, and planting various mixes tailored to soil and site conditions as options.

Another non-IRVM state gave this textbook definition: “Essentially if DOT were to do an evaluation of the roadside to be managed and used the herbicidal, mechanical, and cultural means to address the problem, that would be IRVM as I understand it via NRVMA. Currently we tend to use mechanical first, chemical second, and never in conjunction.”

The employee continues, “Sure I’ve heard of IRVM. I don’t know that we practice it as well as we could. We are a decentralized organization. Trying to get 25 districts to implement any one IRVM program would be tough. I would like to see our managers evaluate a roadside to see what problems exist. Look at what’s there now and develop control thresholds as to when to do what, then consider what controls are to be used when and why. We have trouble integrating spraying and mowing to get the best results of both: allowing chemicals to work before we mow and mowing to optimum heights to promote desirable species.”

Survey questions about specific management practices shed light on what states are actually doing. All 14 states spend at least as much money on mowing as they spend on herbicide application. With one exception, states said their respective programs are much more mechanical than chemical. Some spend up to 10 times as much money on mowing as on herbicide application. Annual mowing expenditures for these states ranged from $500,000 to $40 million per year. Most of these states indicated that they try to avoid mowing the entire right of way and mow to maintain a clear zone (recovery area for errant vehicles) and provide necessary visibility.

Even a Mowing Program Can Be Integrated

Arkansas has been reforesting an excess right of way for years. The rest of the right of way was a high-maintenance zone getting mowed four times a year. Since they were mowing all the way up to the reforestation area each time, Arkansas DOT’s Philip Moore worried that they were mowing their herbaceous natives out of existence. He recommended reducing the high-maintenance zone to a 10-ft.-wide strip and leaving a 25- to 30-ft.-wide “transition” zone that gets mowed just once a year. The single mowing is necessary to keep woody plants from taking over the wildflowers. Mowing in the high-maintenance zone is reduced to three times a year and is timed to promote wildflowers, according to Moore. “Some people do not care for the reduced mowing. But now over half of public comments favor the reduced mowing.” A few people are unhappy that the transition zone gets mowed at all.

Inconsistencies between maintenance areas plague most states. According to Bob LaRouch of Maine DOT, it’s up to the seven individual maintenance divisions to decide whether to mow. “Some mow only along interstates, some mow along secondary roads, and some do not mow at all.”

Paul Northcutt says Texas DOT does a lot of strip mowing with a 15-ft. Batwing mower. “Generally we do two strips in spring and fall. Mowing guidelines recommend a non-mow or natural zone also. How this is carried out varies from district to district. They are encouraged to mow the minimum.” He says results vary. One homeowner located between two districts continually complains about the inconsistent practices of the two. “One district mows six times a year, the other mows one or two strips twice a year.”

Gary Henry of Florida DOT says, “We probably do more mowing than anybody else in the country. But not much spraying. Southern Florida is full of noxious weeds. Just like people, they come here, like the climate, and wind up staying.” Florida’s water table is often only a foot below the surface, so a few years ago DOT was required to reduce chemical use. Now the weeds are controlled with lots of mowing: 16 times a year.

Mowing for brush control is pretty universal, notes Debby Brown of Ohio DOT. “We mow a clear zone three times a year. We do a fourth mowing that is a mow-back when the entire right of way is mowed for brush control.”

Mowing can also be politically motivated. Scott Wheeler of Michigan DOT says, “We are currently in a transition period because of some new legislation reducing the mow-strip width. On limited access roads, it is going from 15 feet down to 12 feet with the exception of roadsides that fall within the boundaries of federal-aid areas.” This exempt area includes the city of Detroit, which accounts for half the annual mowing expenditures. In Detroit they can mow all they want. The more they mow, the happier it makes politicians concerned with projecting the right image.

According to Don Cober of Maryland DOT, politics figures into some of their mowing practices as well. “A few years ago we tried a ‘grow, don’t mow’ campaign that made the governor quite mad.” It seems he likes a very controlled look. “Now we mow a whole lot more. The whole right of way gets mowed every three to four weeks, sometimes more.”

We’ll Be Using Harmless Chemicals Sooner Than No Chemicals

People talk about cultural controls and biological control. And state DOTs are looking into these practices, but there isn’t much going on. Roadside vegetation management is mostly mechanical and chemical, usually doing more mowing to reduce chemical use. According to Phil Johnson of Montana DOT, “The county where the University of Montana is located banned herbicides for a while.” Local residents were holding up Iowa’s Integrated Roadside Vegetation Management Technical Manual, saying, “Look what other states are doing.” “We tried to control weeds with fire, revegetation, and handpulling,” states Johnson. “We tried integrated weed management for spotted knapweed and found cultural controls ineffective.”

Some states are fortunate in that they do little herbicide spraying anyway. John Samson of Wyoming DOT says, “We have cut herbicide use greatly over the last 10 years. We use some plant-growth regulators and spray for kochia and Russian thistle.” LaRouch of Maine DOT says his state has no noxious-weed law.

The level of agricultural activity in a state has a lot to do with the intensity of its roadside weed-control program. According to Moore of Arkansas DOT, “The Mississippi Delta third of the state is the intense agricultural zone. They want more weed control there.” For Arkansas, this involves both spot treatment and broadcast spraying.

Using sterilants to maintain bare ground is common among these states. This is done on the shoulder and especially along guardrails and signposts. On the brighter side, a few states indicated that their chemical expenditures have gone down significantly over the past several years.

Sometimes spending more can save money. Texas DOT’s Northcutt says, “We cannot control the brush with just mowing. We are doing a lot of labor-intensive backpack chemical application. We get 98 percent kill this way over a two-year period, whereas if we blanket spray, we get only 50 percent kill.”

What We Plant Is Becoming More Important

Most proponents of IRVM believe in establishing a healthy, sustainable plant community as the best way to reduce roadside maintenance. Planting native species or at least some well-adapted, low-maintenance vegetation is a proactive approach to weed control. As Montana DOT’s Johnson puts it, “Instead of watching them fight undesirables, I’d like to see them plant desirables.”

Ed Phillips of Alabama DOT indicates that they have a different low-maintenance mix for each of three climatic zones from the gulf to the foothills. “The goal is the opposite of diversity. We plant Bermuda grass because it requires mowing and Bahiagrass in the gulf area because it is more drought-tolerant. The new governor is very supportive of wildflower plantings, so efforts are expanding. But wildflowers will account for less than 10 percent of our plantings. We use some natives in the wildflower mix, but these are not as showy.” Part of the Alabama governor’s initiative includes not mowing beyond the clear zone, allowing the remaining area to revert to a natural state for habitat.

Alabama was not the only state to talk about using wildflowers and not using native grasses. Charlie Nagel of New York DOT says they select plant species for lower maintenance, focusing more and more on native trees, shrubs, and wildflowers, but not grasses. “I don’t feel our native grasses are good candidates since they do not provide quick, dependable, and persistent erosion control.” He notes that little bluestem is native to at least a small part of the state and that big bluestem is native in some parts.

When New York does plant wildflowers, it plants mostly natives, but it doesn’t plant often. “Our wildflower plantings have not been successful,” Nagel admits. “Since they do not persist under the pressure of woody encroachment, they are not low-maintenance or a good use of public funds. And we won’t do flowerbeds.”

For some states, choosing natives for roadsides is not as easy. LaRouch of Maine DOT describes the state as 90% wooded, possibly the most wooded state. “Our natives are trees. The state flower is the white pine tassel.” In roadsides, they plant bluegrass and fescue and a lot of legume non-natives. “We are very happy with crown vetch. We plant some wildflowers, mostly annuals. We have designed mixed plantings to show annuals the first year, followed by lupines for a couple years, and by the fifth year, crown vetch takes over.” He explains that plantings have to be mowed at least once a year, or it’s all trees. He is looking at little bluestem for some utility areas to see if it will compete with cool-season vegetation that far north.

Arkansas traditionally plants a lot of Bermuda grass, lespedeza, and crimson clover. Moore says, “The Keep Arkansas Beautiful program is planting natives.” He is concerned that the natives will not be showy enough. “I added bachelor buttons and poppy to the perennial natives because the media has given the public such high expectations for spring color next year.”

Henry of Florida DOT says, “We do not use native grasses, mostly Bahia and Bermuda. We do use a lot of native shrubs and forbs.” Florida DOT’s Chris Warren describes their extensive wildflower program: “Maintenance units work closely with the local garden clubs, who provide additional seed.” He says that the plantings are well maintained but that he doubts the plantings are native. According to Henry, the nursery business largely ignores natives. “In roadsides, many things just move in, which is our main source of diversity. Some of these are natives, some are not.”

“The drought of the past three years has slowed the wildflower plantings,” observes Maryland DOT’s Cober, “but the mixes are becoming more native.” They have two regional wildflower mixes that are diverse and include natives. “We try to use the right species, but may have to go 500 miles for the seed. It’s not locally available.” Maryland DOT is working with the University of Maryland and the US Department of Agriculture Plant Materials Center to include native grasses. “We are looking at little bluestem, big bluestem, Indiangrass, switchgrass, broomsedge, coastal panicum, and partridge pea.” Their standard grass planting is Kentucky 31 fescue or Kentucky bluegrass and perennial rye.

Sources for native seed are a problem elsewhere. Michigan DOT’s Scott Wheeler says, “Largely because of availability of seed, natives are not used as much as I would like.” Low-maintenance mixes tailored to site and soil conditions are mostly Kentucky bluegrass, perennial rye, and creeping red fescue, with dune grass used in some areas. Part of the problem is the absence of someone to champion the effort. “We have tried some wildflower plantings over the past 20 years. Primarily as a result of woody invasion, they have not been successful.”

Montana is another example of how trees on adjacent land affect roadside plantings. “East of the Continental Divide we use more prairie species,” Johnson explains. “We plant a mix of four short native grasses along the paved surface in a strip l5 feet wide. Beyond that we plant seven or eight grasses and one or two forbs, mostly natives.” The western fourth of the state is forest community with most roads going through intermountain valleys. Johnson says, “These areas revert to shrubs and are not good for grassland species.”

When trying to promote native plants, aesthetics can be a problem, especially closer to town. “At first the intention was to use all native plants,” Paul Edgecomb of Oregon DOT recalls. “We rethought this for city gateways because we realized people view plant materials as a cultural improvement to the area-neat, clean, orderly, tidy, and reflecting on the city.” Oregon uses ornamentals for city gateways.

Oregon has seven major native plant communities from the coast to the high desert and everything in between, including rain forest and 3,000-ft. elevations. “We generally try to balance cost, native vegetation, and function,” Edgecomb points out. “A road might go through an area that has threatened and endangered species, requiring the contractor to harvest seed from the immediate vicinity.” The other extreme is a roadway prone to sliding that needs quick erosion control. “Here we will throw on the most vigorous rye possible.”

In the Midwest it seems everybody manages to get a lot of native species into their roadsides. Ole Skaar of Iowa DOT says, “We still include some fescue and perennial rye for erosion control. But every rural planting is predominantly native.” A standard native mix includes five grasses and at least a half-dozen forbs. A lot of native plantings are happening along Iowa’s county roads as well. Iowa DOT’s Living Roadway Trust Fund helps counties with the purchase of seed and seeding equipment.

Minnesota uses a diverse mix of native species in nearly all roadside plantings and is now focusing on using local seed. Minnesota DOT’s Bob Jacobsen says, “Five years ago we told growers that starting in the year 2000 our priority would be yellow-tag, source-identified seed.” Commercial production fields are started with seed from Minnesota prairie remnants. Iowa is working with local growers and the Iowa Crop Improvement Association to improve local seed sources as well.

At least two states west of the tallgrass prairie are also heavily into the use of native plants. Colorado and Wyoming seem to be doing about as much as any other state. Wyoming DOT agronomist John Samson says, “We plant 99 percent natives. The eastern side of the state uses sideoats grama and little bluestem. In more traveled sections we add three or so native forbs. We use a lot of native shrubs too.” Wyoming has another method that increases natives in the roadside. “We salvage soil on road projects, including the portion with much biological activity. Native plant propagules are preserved in the process and returned to the site.”

Cathy Curtis of Colorado DOT describes their program, “We seed native species almost exclusively. We do not want to include introduced species such as smooth brome and fescue. These establish monocultures and invade wetlands.” Colorado has been mandated to plant species that do not require irrigation. “We want things that are adapted to our harsh climate,” Curtis states. Diversity is also a goal. They use six or seven grasses and a few forbs and shrubs. Mowable mixes are used in urban areas. These are mostly buffalo grass and blue grama. “We are careful about using the right species. As yet we cannot be too picky about the seed source. The park service is able to collect local seed for its plantings. We can only get local seed for wetlands.”

Whether or not they call it Integrated Roadside Vegetation Management, many states are doing it: refining the use of different tools into a comprehensive vegetation management system. Integrating the human factor-whether it’s the governor, the maintenance chief, the equipment operator, or the general public-might be the trickiest part. When it comes to using native species for the right of way, apparently it’s easier for some states than for others. A lot is going on. Some states probably need to give their native grasses a closer look.

In most ways the people at the conference in Louisville are not different from those at the conference in Austin. Everyone wants safe highways. Everyone wants to use public funds responsibly. Everyone wants to protect soil and water. And everyone wants to beautify the landscape. Individual points of view differ. It’s easier for someone not responsible for highway safety to say, “Don’t mow so much.” There does seem to be an almost natural trend to reduce mowing and spraying and to incorporate more native species into plantings.

Better products and technologies are being developed, and management practices continue to evolve. Who knows where this will lead? The network for sharing information between states will affect how efficiently we progress. In the midst of the explosion in communication technologies, it’s encouraging that good conferences where old fashioned, face-to-face encounters are still taking place.

The NRVMA will hold its 17th annual conference in Kansas City, MO, in October 2000. The next Northeast regional Managing Roadsides Naturally Conference will be sponsored by the Native Plant Center and held on November 3, 2000, at Westchester Community College in Valhalla, NY, and the next national conference will be held at the Lady Bird Johnson Wildflower Center in fall 2001.
About the Author

Kirk Henderson

Kirk Henderson, Ph.D., is with the University of Northern Iowa's Department of Biology in Cedar Falls, IA.