Southern Research Station Headquarters - Asheville, NC

September, field covered in congongrass. Photo by Jim Miller.

Cogongrass Imperata cylindrica (L.) Beauv

Synonyms: japgrass, bloodroot grass (red varieties), Red Barron (red varieties)

Aggressive, colony-forming dense perennial grass 1 to 5 feet in height, often forming dense mats when over 3 feet in height. It has tufts of long leaves, blades yellow green, with off-center midveins and silver-plumed flowers and seeds. Cogongrass is spreading rapidly across the Southeast, reducing forest and pasture productivity, destroying wildlife habitat, impacting right-of-ways and presenting an extreme fire hazard.

Ecology. Grows in full sunlight to partial shade, and, thus, can invade a range of sites. Often in circular infestations with rapidly growing and branching rhizomes forming a dense mat to exclude most other vegetation. Aggressively invades right-of-ways, new forest plantations, open forests, old fields, and pastures. Absent in areas with frequent tillage. Colonizes by rhizomes, spreads by wind-dispersed seeds, and promoted by burning. Highly flammable and a severe fire hazard, burning extremely hot, especially in winter.

Resembles Johnsongrass, Sorghum halepense (L.) Pers.; purpletop, Tridens flavus (L.) A.S. Hitchc.; silver plumegrass, Saccharum alopecuroidum (L.) Nutt.; and sugarcane plumegrass, S. giganteum (Walt.) Pers.—all having a stem and none having an off-center midvein.

History and use. Introduced from Southeast Asia into Florida and southern Louisiana, southern Alabama, and southern Georgia in the early 1900s, initially for soil stabilization. Expectations for improved forage unrealized. A Federally listed noxious weed.

Stem. Upright to ascending, stout, not apparent, and hidden by overlapping leaf sheaths.

Leaves. Mainly arising from near the base, long lanceolate, 1 to 4 feet long and 0.5 to 1 inch wide, shorter upward. Overlapping sheaths, with outer sheaths often long hairy and hair tufts near the throat. Blades flat or cupped inward, bases narrowing, tips sharp and often drooping. Most often yellowish green. White midvein on upper surface slightly-to-mostly off center (varies in an area). Margins translucent and minutely serrated (rough).

Flowers. February to May (or year-round in Florida). Terminal, silky spikelike panicle, 1 to 8 inches long and 0.2 to 1 inch wide, cylindrical and tightly branched. Spikelets paired, each 0.1 to 0.2 inch long, obscured by silky to silvery-white hairs to 0.07 inch.

Seeds. May to June. Oblong brown grain, 0.04 to 0.05 inch long, released within silvery hairy husks for wind dispersal.

Recommended control procedures:

• Thoroughly wet all leaves with one of the following herbicides in water with a surfactant (September or October with multiple applications to regrowth): Arsenal AC* as a 1-percent solution (4 ounces per 3-gallon mix), a glyphosate herbicide as a 2-percent solution (8 ounces per 3-gallon mix), or combination of the two herbicides.
• Repeat before flowering in spring to suppress seed production and again in successive years for eradication.

* Nontarget plants may be killed or injured by root uptake.

From: Miller, James H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. Gen. Tech. Rep. SRS-62. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p.

November 7th and 8th, 2007: Cogongrass Conference: Confronting the Cogongrass Crisis Across the South at the Arthur R. Outlaw Mobile Convention Center in Mobile, Alabama.

James H. Miller  334-826-8700 ext. 36 jmiller01@fs.fed.us

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