By: Roads & Bridges
The North Carolina Department of Transportation (NCDOT) Roadside Environmental Unit has successfully developed an Integrated Roadside Vegetation Management Program to cater to the more than 58 million visitors traveling by car each year throughout the state. NCDOT crews work exceptionally hard to maintain the safety and appearance of 300,000 acres of rights-of-way (ROWs) along more than 78,000 miles of highway. They also manage one of the most spectacular roadside wildflower programs in the country, similar to the Lady Bird Johnson Wildflower Program in Texas.
NCDOT works statewide across three climate zones: coastal, piedmont and mountain. These regions include multiple cool- and warm-season grass species, as well as varying soil conditions.
Traditionally, NCDOT had been mowing ROWs to maintain grass heights, spending up to $21 million annually on mowing operations. In the last 15 years, however, NCDOT also began controlling grasses using herbicide programs crafted with the help of BASF Professional Vegetation Management (ProVM).
In eastern coastal areas, NCDOT deals primarily with warm-season grass species, such as bahiagrass, centipede grass and Bermudagrass. The vegetation management priorities in this region are suppressing bahiagrass seed heads and converting bahiagrass to centipede grass. On average, these warm-season grass areas would require three to five costly mowings per year without the aid of herbicides.
Instead, the NCDOT uses Plateau herbicide to suppress bahiagrass seed heads. Applying 3 to 4 oz. of the herbicide per acre in the spring saves NCDOT at least one mowing every year.
The second priority for warm-season grass management in eastern North Carolina is converting bahiagrass to centipede grass. Unlike bahiagrass, centipede grass does not produce seed heads as quickly and, if left unmowed, it grows only 4 to 6 in. tall, making it a popular choice for ROWs. By converting ROWs to centipede grass, NCDOT can cut its maintenance cycle by two or more mowings per year.
To prepare a site for planting desirable grasses, the NCDOT applies Plateau at a 4- to 6-oz.-per-acre rate between April and June, just before bahiagrass usually begins forming seed heads.
To maintain cool-season grasses, such as tall fescue, in the mountains of western North Carolina, NCDOT follows a plant growth regulator (PGR) program that also utilizes Plateau. As with bahiagrass, NCDOT’s cool-season PGR program helps stunt the height of tall fescue by suppressing seed-head production.
While tall fescue is an ideal cool-season grass species for erosion control, it can grow up to 4 ft tall, decreasing visibility of road signs and hazards and requiring five to seven mowings per year. By applying Plateau in March or April, NCDOT can reduce cool-season grass mowings to no more than four to six times per year.
By incorporating seed-head suppression herbicide treatments into its vegetation management program, NCDOT saves between $1 million and $1.5 million annually.
“Any money we can save on mowing can go toward other aspects of our environmental projects,” Smith said. Herbicide treatments have greatly enhanced the wildflower and native plant programs at NCDOT.
