Natural & Cultural Stewardship

TDOT and Sewanee work together to protect endangered plants on Cumberland Plateau

Wed, 04 Nov 2015 14:25:00 CST  — by: Callie Oldfield

Sewanee and the Tennessee Department of Transportation (TDOT) have been working together to protect rare plants and native wildflowers that grow along roadsides in the Sewanee area. Typically, plants growing roadside are mowed and sprayed with broad spectrum herbicides in order to prevent their growth into the road area. These herbicides eliminate the trees that pose the greatest safety threat, but they can also kill forbs and herbs, including endangered species such as Cumberland rosinweed (Silphium brachiatum).

Cumberland rosinweed is a south Cumberland Plateau endemic in the daisy family. Cumberland rosinweed can be found along US Hwy 41A, which runs through the Domain and state-protected natural area Hawkin’s Cove; this natural area was acquired by the state in 1985 in order to preserve its habitat. Other rare and unusual plants that have been subject to right of way spray in the past include: eared goldenrod (Solidago auriculata), Morefield’s clematis (Clematis morefieldii), cylindrical blazing star (Liatris cylindracea) and cut leaf prairie dock (Silphium pinnatifidum).

Domain Manager Nate Wilson and PPS Grounds Supervisor William Shealy helped spearhead this initiative to protect native wildflowers through designing new management practices. Sewanee made two recommendations: First, to allow TDOT to go off of their road right of way and into roadside Sewanee property to prune trees in a more aesthetically pleasing way that also lessens the tree’s tendency to exhibit vigorous regrowth, and second, to design a new herbicide spray formula that targeted the problem woody species while promoting grasses, forbs, and wildflowers.

For 6 months, Nate worked with a TDOT botanist and a DOW Chemical Company representative to come up with a new herbicide formula that will target only trees, because “trees are the threat [to the roads], not the grasses or forbs we are trying to protect.” The new formula will deaden only the portion of the trees touched by the spray and prevent that part of the tree from producing leaves in the spring, but will not harm forbs or herbs. As a result, fewer trees will need to be chopped or mowed, and our endangered species and native wildflowers will be protected. 

TDOT sprayed this herbicide in the Sewanee-area for the first time last month and is considering adopting the practice more widely in the future.

Silphium brachiatum

Photo courtesy of Mary Priestly.

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