Advances in Vegetation Management

July 1, 2006

Perry Odom knows rain. He works in the city of Tallahassee, FL, where he serves as a forester for the city’s electric department. As anyone who’s ever spent time in the city knows, Tallahassee is one metropolis where rainy days come frequently and where residents know the value of a good umbrella.

For Odom, though, rain is more than just an inconvenience. All that water-not to mention Florida’s high humidity and persistent heat-means that Tallahassee is a perfect spot for trees to grow large and lush, and to do it quickly. All those large trees can play havoc with the city’s electric service. After all, trees, and their drooping or falling branches, cause more outages for the City of Tallahassee Electric Department than does any other nuisance. It’s essential, then, for the department to control the trees and other vegetation growing along the electric utility’s overhead distribution lines and transmission lines.

“Down here in Florida, the trees seem to grow faster than they do anywhere else,” Odom says. “They have a 10-month growing season. Some trees never go dormant.”

Odom’s department meets the challenge not by relying on just one technique to manage the vegetation growing in the utility’s public rights of way. Instead, the contractors hired by the department-crew members from Asplundh Tree Expert Co., a national vegetation-management company-turn to a variety of methods to prune trees, clear away shrubs, and prevent unwanted vegetation from sprouting. Crew members use heavy-duty mowers to clear out the rights of way, aerial buckets to trim large tree branches, tree-growth regulators to reduce the amount of new growth on existing trees, herbicides in sensitive areas where the department wants no growth at all, and other chemicals to prevent the stumps of freshly cut trees from sprouting again.

Odom and his contractors are not unusual. This integrated approach, combining both mechanical and chemical means, is becoming more common among innovative highway departments and utilities.

Municipal and utility officials face several challenges when it comes to controlling the weeds, trees, and shrubs growing along their roads or transmission lines. Utilities, for instance, are expected to provide uninterrupted, reliable service. Unpruned trees along the rights of way sometimes make this an impossibility. And unchecked growth along busy roads can lead to reduced visibility for drivers.

Combating vegetation, though, is not an easy task. Many rights of way abut private property, and homeowners and corporations may put additional pressures on clearing crews. Property owners may complain that severe cutting and trimming causes an eyesore. These same owners may not want herbicides applied near their property lines. Crews working alongside busy highways can easily place themselves in physical danger. And, just as importantly, controlling vegetation is far from an inexpensive proposition. Sharon Vore, system forester for Avista Utilities, a small investor-owned utility based in Spokane, WA, estimates that her utility spends from $4 million to $5 million a year on vegetation management.

These challenges are why many utilities and highway departments are turning to an integrated approach to manage their right-of-way vegetation. Still, for every innovative utility, there is another that refuses to experiment with anything besides regular cutting to manage vegetation. Industry pros predict, though, that integrated efforts will only grow in popularity as more users find success with such an approach.

“I think we are in a changing environment,” says Bill Massey, tree growth regulator specialist with Carmel, IN-based SePro Corp., which provides plant-growth regulators. Such an approach, Massey says, results in less cutting and expense in the future. “The problem, though, is that there is a lot of turnover in this business,” he notes. “I get someone onboard, but then he may get a promotion or move to another utility. Then someone comes in with no experience and I have to start at ground zero again. The concept is out there, though. People are using it and seeing cost impacts and the benefits it brings to their utilities. Everyone, though, wants to see how it works on his or her site. They don’t want to hear that another county over in the other half of the state has had success. They want to know what it can do for their utility. Everyone wants to run his own test.”

A Multifaceted Approach
Proof of municipal officials’ desire to take a more integrated approach to vegetation management is largely anecdotal. But those anecdotes are starting to pile up.

This makes sense. By using all the options available to them, highway departments and public utilities save precious dollars in the long run. Through the judicious use of herbicides and plant-growth regulators, these departments can lengthen the stretch of time between pruning or trimming cycles. By relying on the most advanced mowers-those featuring, for instance, saw-blade technology that is safer and more efficient than traditional rotary blades-municipal officials can cut more vegetation more quickly, shortening the amount of time crews are actually onsite.

Studying new approaches to vegetation management is so important that some highway departments work in conjunction with scientists and researchers to develop new methods. This is the case with the Kentucky Transportation Cabinet and Mitch Blair, a research scientist at the University of Kentucky. Blair is studying ways to help the state transportation cabinet better control the weeds in its roadside rights of way. Basically, Blair tests herbicides and new methods of applying them and growth regulators and then presents the findings to employees of the cabinet.

While some may see the partnership as unusual, Blair himself does not. “It’s not necessarily a new trend,” he says. “What’s been happening is that people are starting to pay more attention to matters such as herbicide selectivity. They are more interested in being able to use certain chemicals that control problem species while still letting desirable ones come through. They may want to control a broad-leaf weed but let the grasses surrounding it remain. That can be important when trying to control invasive species. You want to use chemicals that allow the desirable species to grow back while eliminating the invasive ones.”

Blair is working under a two-year grant that has been extended two additional years to study new chemical means of treating vegetation along Kentucky’s roads. The task is a big one, as the state’s rights of way, Blair says, are corridors that are prime for invasive species.

The invasive species that Blair is studying are a mixed lot, varying according to the parts of the state in which they are located. In the eastern portion of Kentucky, which features narrow rights of way on steep terrain, kudzu and Japanese knotweed are some of the more common invasive species with which highway officials have to deal. In central Kentucky, where the land is flatter and rights of way abut adjacent horse farms and small agriculture farms, municipal officials struggle to contain Johnson grass and kudzu. Western Kentucky features land that is very flat and home to larger agricultural farms. Again, kudzu is a problem here, but so are several aquatic and terrestrial plants.

Blair’s mission is to quantify how large Kentucky’s population of invasive species is and how best state officials can contain and weaken that population. “We are taking an inside-out approach,” he says. “It’s easier for land managers to control species if they know how much they have and where it is. That’s better than running around crazy in spray trucks when you don’t know how much you’re dealing with and where it is.”

Blair is currently working on a pilot mapping program in Fayette County, home of Lexington, KY, that started last summer. He and his fellow researchers are mapping where various invasive infestations are located in the county. The hope is that municipal officials will study Blair’s maps to chart out better application techniques when using chemicals to battle roadside vegetation. Blair also hopes that officials can rely on the map to determine where new infestations may spread. For instance, if one corner of the county is heavily infested with Japanese knotweed, the chance is good that without action the invasive may spread to a neighboring section of the county.

“I think of it as the state being proactive instead of reactive,” Blair says. “It’s thinking outside the box a little bit.”

Preventing Problems Before They Start
Blair’s work in Kentucky is far from the only scientific approach researchers are taking toward vegetation management. Dearl Sanders, a professor at Louisiana State University and coordinator for that school’s AgCenter, is right now studying the impact that Hurricanes Katrina and Rita may have had on the spread of invasive species throughout not only the state but across the rest of the country.

This may not seem at first glance like an issue about which officials with departments of transportation or public utilities need to worry. But the spread of invasive species can actually have a direct impact on right-of-way vegetation, Sanders explains.

One of the invasive species that may have been spread through the Gulf Coast region following the hurricanes is cogon grass, Sanders says. This is a grass that grows well along areas such as rights of way. Even worse, it’s hard to kill the grass chemically without spraying it with chemicals that will also kill other, more desirable vegetation. The Japanese climbing fern is another invasive that rescue workers and other first-responders to the hurricanes may have spread to other parts of the state and Gulf Coast, Sanders says. This is another species that thrives in rights of way, often growing 40 to 50 feet up along power line poles and signs. “It’s a real nuisance on roadsides,” he notes.

Sanders recently spoke about the spread of invasive species in Washington, DC, in front of land managers from both state and federal agencies as part of National Invasive Weed Awareness Week. His hope was that the members of his audience, alerted to potential problems, would be inspired to take action to prevent invasive species from spreading to their areas.

“We had some pretty good evidence that all of the movement in Louisiana, primarily the rescue and revitalization process that took place after the hurricanes, is operating in an area rife with invasive species,” Sanders says. “There’s a pretty good chance that some of those species were moved out of state.”

This is hardly surprising. Nearly 100,000 people moved short-term into the state shortly after the hurricanes, bringing with them nearly as many vehicles. “They were operating in this coastal zone that is a big pile of debris, mud, and muck,” Sanders says. “The invasive weeds survived the flood quite well. Some of the seeds have been transported back to wherever these vehicles came from. There was no way to clean these vehicles up until they got home. We had no running water.”

Sanders has developed a list of 12 invasive weeds that he believes have been spread out of state in the aftermath of the hurricanes. They include some particularly nasty invasive species that can cause serious problems for right-of-way vegetation management: itchgrass, torpedo grass, and the Bengal dayflower.

The spread of invasive species is a relatively minor problem for the officials of the Gulf Coast regions hit hardest by the hurricanes. “We are still in a recovery and rescue phase in Louisiana,” Sanders says. “This is not the biggest issue we face. I’m just trying to give people a heads-up. This is not my mission. I just want to let them know they have a problem that they may not realize yet.”

New Measures in an Old Fight
Highway departments and public utilities have been battling right-of-way vegetation for decades. Today they have more weapons available in their fight.

For example, Alamo Industrial based in Sequin, TX, has long provided mechanical tools to help control roadside vegetation. Today, though, those tools are more advanced than ever.

The company’s Buzz Bar is a limb cutter that uses a 26-inch saw blade as opposed to a rotary motor. The company has also introduced a series of flail mowers that provide a finer cut than does a rotary mower. Flail mowers are also safer for operators than are rotary versions.

Part of the impetus behind such advancements is that the public-especially those owners whose properties lie adjacent to rights of way-is demanding that cutting crews handle vegetation management in a sensitive manner that results in aesthetically pleasing work. Utilities and highway departments that want to stay on the good side of the public, always a laudable goal, will do well to listen and to use equipment that produces more visually pleasing cuts.

“The old idea was to cut as much as you possibly could as quickly as you could,” says Ian Burden, executive vice president with Alamo. “That left trees sometimes looking a bit ragged. We have introduced products over the past three to five years that are using saw-blade technology so that the finished appearance of a job is aesthetically much more pleasing for the general public to look at. This was in response to public works directors who had contacted us. They had cleared the road and the public complained to them about the look of the job. Everyone is really being forced to push the technological advantages of equipment and respond to what the public wants in a safe manner.”

Safety, too, has improved over the years, Burden says. Today operators work almost exclusively in tractors with air-conditioned cabs mounted to them, something that has not always been the case. Decibel levels are regulated so as to protect the hearing of operators. Equipment itself goes through several more rounds of testing before being introduced to the market.

Government officials are now more likely to consider other factors besides price when deciding which vegetation-management equipment to purchase. “In the past, governmental agencies seemed more likely to strictly buy equipment on a price basis,” Burden notes. “They were looking for the cheapest they could possibly do. With more sophisticated public works managers, they are looking at the total operating costs. They are taking into account the technological advances that we can offer with our equipment. They realize that those advancements bring them advantages, even if they have to spend a little bit more money up front.”

More Than One Solution
Controlling erosion is an important matter for Rick Lipcsei, civil project manager for the Georgia Transmission Corp. The corporation, owned by 39 electric cooperatives in Georgia, builds high-power transmission lines. The contractors it hires are often charged with clearing out large swaths of trees and vegetation to make room for these lines.

In doing this work, Lipcsei’s contractors rely on a host of products. They use land-clearing equipment from Shinn Cutter Systems and mowers from Bush Hog. Perhaps the biggest difference, though, in the way contractors handle their land-clearing work now is the amount of attention they place on controlling the erosion that can result when land is stripped of a large amount of its vegetation and trees.

For instance, crews use Shinn Cutter attachments to quickly turn trees into piles of wood chips. In doing so, these crews, as often as possible, bring felled trees to what Lipcsei calls zero-ground level. This means there’s no large stump poking above the earth. This leaves little exposed earth and a decreased opportunity for soil erosion.

Clearing crews also leave at least 4 to 6 inches of wood chips behind to help stabilize the ground, Lipcsei says. Workers install silt fences, too, and let water run through the chips and then through the fence.

“In the old days, we’d take trees down and haul them out,” Lipcsei says. “That’s all changed. Now we chip them. That saves us gassing and mulching and all that. It works fast. It’s effective. The big difference now from in the past is that we are more concerned about preventing soil erosion and using the proper BMPs for the project. Woodwaste used to be considered a cost item. Now chips are a valuable tool in our BMP toolbox.”

Managing vegetation has long been a primary concern for Avista Utilities’ Sharon Vore. The utility serves eastern Washington and northern Idaho and is responsible for about 2,500 miles of transmission corridors and about 8,500 miles of distribution lines.

Vegetation management is the largest program the utility runs, Vore says. The reason is simple: Trees are one of the biggest causes of outages for Avista. It’s important, then, to maintain them.

The utility deals with two kinds of lines, rural and residential. The rural lines, both distribution and transmission, are located away from roads and generally move through a clear corridor. The residential lines are more problematic. Keeping them clear requires the certified arborists hired by Avista to continually prune ornamental trees to keep their branches away from wires.

“This is labor-intensive and time-intensive,” Vore says. “From an aesthetic point of view, it also gets tough at times. We work with a lot of homeowners, and we deal with a lot of private trees or street trees that are in front of people’s homes.”

It is in these residential areas that Avista’s arborists turn to tree-growth regulators. By applying the regulators, arborists can slow the growth of these trees and don’t have to return to cut or prune them as often.

How effective are the regulators? Typically, arborists return to each residential tree every three to four years to prune it. After treating trees with growth regulators, though, arborists need return only every six, seven, or eight years, Vore says. This saves money and time, of course, but also lessens the possibility of tensions with homeowners who don’t enjoy seeing their full trees trimmed.

Vore says Avista spends from $4 million to $5 million every year on its vegetation-management program. That’s a lot of money for a relatively small utility-though extremely large utilities may spend $30 million to $40 million annually managing trees and weeds-but Vore says the cost is worth it. Avista, like all utilities, faces constant pressure to provide reliable service. Whenever an overgrown tree branch falls and downs a power line, it’s one more series of headaches for Avista: The company has to send out repair crews, provide information on the outage for angry customers, and spend money and time repairing the damage. By preventing the branches from falling in the first place, the utility can stop the headaches before they start.     

Besides its regulators and mowing machines, Avista’s contracted arborists also use herbicides to control vegetation in the utility’s rights of way. Often, crews spray these chemicals in targeted areas where they are trying to discourage the growth of invasive species or troublesome taller species.

“Basically, we are trying to increase plant diversity, but we are also trying to change the composition of the plant community from a forest to low-growing compatible tree and shrub species,” Vore says. “We don’t want to completely clear the rights of way. We want to maintain them by encouraging native low-growing plants. We’d like to use bio-diversity to encourage the low-growing plants to fill in and prevent the tall-growing plants from coming.”

Plants that Vore would like to see more of along Avista’s rights of way include ferns, which do a good job of keeping away taller conifers; service berry; wild roses; berry bushes; and any kind of herbaceous vegetation.

Unlike Odom in Florida, Vore and her crews don’t have to worry about dealing with much rainfall. Vore says many of the areas in the utility’s service territory only get 10 to 12 inches of precipitation a year. In heavy rainfall years, the precipitation still rarely comes in higher than 40 to 45 inches a year. These are low numbers, so trees and weeds here don’t grow quite as fast as they do in wetter areas of the country.

But that doesn’t mean Avista’s service area is challenge-free. Because the area is largely dry, the region faces high fire danger if trees and dry vegetation aren’t maintained. Arborists must deal with a high number of dead and dying trees along the area’s rights of way. Avista crews spend significant amounts of time patrolling for dangerous trees.

Just the fact that Vore can so easily reel off her region’s unique challenges and, more importantly, can choose from a wide variety of measures to meet them is further proof that the field of vegetation management is becoming a more scientific and resourceful one.

“I’ve been doing this for more than 20 years,” Vore says. “There is so much science involved in this field now. There is so much research going on. It’s really been a positive change.”

About the Author

Dan Rafter

Dan Rafter is a technical writer and frequent contributor.