Cogongrass
Imperata cylindrica (L.) Beauv.

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.

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

Plant. Aggressive, colony-forming dense perennial grass 1 to 5 feet (30 to 150 cm) in height, often leaning in mats when over 3 feet (90 cm) in height. Stemless tufts of long leaves, blades yellow green, with off-center midveins and silver-plumed flowers and seeds. Plants arising from branching sharp-tipped white-scaly rhizomes.

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 (30 to 120 cm) long and 0.5 to 1 inch (12 to 25 mm) 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). Ligule a fringed membrane to 0.04 inch (1.1 mm).

Flowers. February to May (or year-round in Florida). Terminal, silky spikelike panicle, 1 to 8 inches (2.5 to 20 cm) long and 0.2 to 1 inch (0.5 to 2.5 cm) wide, cylindrical and tightly branched. Spikelets paired, each 0.1 to 0.2 inch (3 to 6 mm) long, obscured by silky to silvery-white hairs to 0.07 inch (1.8 mm).

Seeds. May to June. Oblong brown grain, 0.04 to 0.05 inch (1 to 1.3 mm) long, released within silvery hairy husks for wind dispersal.

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 and 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 Federal listed noxious weed.

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.

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