Cogongrass: Worse than Kudzu?

by Tracy E. Outlaw

According to researchers at the University of Florida, it is.

Cogongrass (Imperata cylindrica), considered one of the ten worst weeds in the world, was recently planted in at least four locations in South Carolina – by a person who mistakenly thought that it was a native plant.  Instead, it is a federal and state noxious weed.  The Department of Plant Industry (DPI) is now working with landowners to eradicate the cogongrass on those sites.  A purple form of this grass called “Japanese Bloodgrass” is sold as an ornamental plant in many states, even though it can revert to the green, highly-invasive form.  The sale of all forms of Imperata cylindrica is prohibited in South Carolina.

Cogongrass is an erect perennial plant that can grow up to five feet tall.  It spreads vegetatively and by seeds.  The seeds are tiny and are easily spread by the wind, animals, and vehicles.  The plant can also spread vegetatively by rhizomes, which become very dense in an established stand.  Over three tons of rhizomes may be produced per acre.  The rhizomes are typically found in the top six inches of soil, but some have been found in areas up to four feet deep.  Because of its network of rhizomes, cogongrass is able to conserve its own water and withstand drought conditions.

Cogongrass grows in tufts that can become very compact under favorable climate conditions.  Each tuft has several sharply pointed leaves that grow out of a central area along each rhizome.  This mass of rhizomes and dense foliage quickly overtakes an area and excludes other vegetation from growing, displacing native plants and the birds and other small animals that use those plants for foraging and shelter.

Earlier this year, Clemson University Forestry Extension, along with the Department of Plant Industry, joined forces with the U.S. Forest Service, S.C. Forestry Commission, and environmental organizations to form a 15 member Cogongrass Task Force.  The group’s goal is to work together to eliminate cogongrass sites already in our state and to combat further spread of this noxious weed through public awareness campaigns, best management practices, careful monitoring, and control.

Worldwide, cogongrass has infested 1.2 billion acres.  In Florida alone, it has invaded over one million acres.  The weed is difficult to control, even with repeated pesticide applications.  Controlled fires are not effective. Cogongrass plants burn 20 to 25 degrees hotter than other brush and foliage, which kills trees and opens the forest for further invasion.

For more information about cogongrass and other invasive plant species, contact Steve Compton at the Department of Plant Industry.

Page maintained by: LeAnn Carver, leannc@clemson.edu