SRS Forest Inventory and Analysis data indicate that cogongrass currently grows on over 46,000 forested acres—and counting— throughout the Southern United States. “This does not take into account the thousands of unsurveyed acres occupied by cogongrass in nonforested settings,” says Miller, an ecologist with the SRS Insects, Diseases, and Invasives Plants unit in Auburn, AL. “Because cogongrass is a fast moving and destructive plant that can thrive almost anywhere, the entire Southeast is at risk for invasion.”

Each cogongrass plant can produce as many as 3,000 winddispersed seeds that can germinate on disturbed soil. Cogongrass also spreads by underground stems known as rhizomes that form dense mats reaching deep into the soil. The rhizomes have pointed tips—sharp enough to pierce the roots of nearby plants—that send out shoots and branches that multiply and grow, expanding into colonies that can completely exclude other vegetation, even kudzu.

“The rapid spread of cogongrass can primarily be attributed to seeds and rhizomes that hitchhike on mowers, equipment, hay, fill dirt, and rocks being transported out of infested zones,” says Miller.

Cogongrass can apparently tolerate all light and soil conditions except dense shade and permanently wet soil, so most habitats in the South are fair game. Once established, it is extremely difficult to control.

Fire doesn’t slow down the invader; cogongrass itself is a fire hazard to be taken seriously. The plant burns readily, even when green and especially when plant tops have browned and dried in the winter. Homes and structures in the wildlandurban interface and in suburban areas are increasingly at risk due to the unnaturally hot and fast wildfires produced by ignited cogongrass. Following a fire, the surviving rhizome system allows cogongrass to quickly regenerate and continue spreading.

The spread of cogongrass has so far been limited to temperate areas with relatively mild winters, but that could change.

Red Baron or Japanese blood grass, an ornamental variety of cogongrass used in landscape plantings, is cold hardy. As of yet, the cultivar does not produce viable seed, but its pollen is viable.

“There is real potential for the cold hardiness that has been bred into the red varieties to be imparted to invasive cogongrass populations through pollen,” says Miller. “If this occurs, the whole United States and southern Canada would be open for invasion.” This concern has prompted several Southern states to prohibit the sale and distribution of the cogongrass cultivar.

Proactive control and eradication of cogongrass and, ultimately, rehabilitation of infested lands in the South is an ongoing challenge. “Cooperation and education on a grand scale are needed to rid the South of cogongrass,” says Miller. “But preventing cogongrass from becoming established in the first place will be the best—and least costly—solution to this problem.”

For more information:

Jim Miller at 334–826–8700, x36 or jmiller01@fs.fed.us

Recommended reading:

Loewenstein, N.J.; Miller, J.H., eds. 2007. Proceedings of the regional cogongrass conference: a cogongrass management guide. Auburn University, AL: Alabama Cooperative Extension System. 77 p.