Cogongrass (Imperata cylindrica)
Miller, J.H., E.B, Chambliss, N.J. Loewenstein. 2010. A Field Guide for the Identification of Invasive Plants in Southern Forests. General Technical Report SRS-119. Asheville, NC. United States Department of Agriculture, Forest Service. 126 p.
Aggressive, colony-forming dense perennial grass 1 to 6 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. Silver-plumed flower and seed heads in late winter (south) through early summer (north). Plants arising from branching sharp-tipped white-scaly rhizomes. Federal noxious weed.
Upright to ascending, stout, not apparent, as hidden by overlapping leaf sheaths that are long hairy or not.
Mainly arising from near the base, long lanceolate, 1 to 6 feet (30 to 180 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 to touch). Ligule a fringed membrane to 0.04 inch (1.1 mm). Tough to break due to high silica content. Tan colored and persisting after winter dieback.
February to June and sporadically (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 on a reddish slender stalk. Spikelets paired, each 0.1 to 0.2 inch (3 to 6 mm) long, obscured by tufts of silky silvery-white hairs to 0.07 inch (1.8 mm).
May to June. Tiny oblong brown grain, 0.02 to 0.05 inch (0.5 to 1.3 mm) long, released within dense tufts of silvery hairy husks, often in clusters, for wind dispersal. Seeds matured after V-shaped stigma pair at grain tips shrivel and darken.
Grows in full sunlight to partial shade, dry to wet soils, and, thus, can invade a range of stands and sites. Often in circular infestations through rapid growth of branching rhizomes that fill friable soils to a depth of 0.6 to 10 feet (0.1 to 3 m) 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, but promoted by burning. Colonizes by rhizomes and spreads by wind-dispersed seeds, seeds and rhizomes contaminating soil and hay, and hitchhiking rides on mowing, logging, and other equipment. Seed fertility highly variable across the region. Highly flammable and a severe fire hazard, burning extremely hot especially in winter.
Resembles Johnsongrass, [Sorghum halepense (L.) Pers.], purpletop [Tridens flavus (L.) Hitchc.], silver plumegrass [Saccharum alopecuroides (L.) Nutt.] and sugarcane plumegrass [S. giganteum (Walter) Pers.]—all having a distinct stem and none having an off-center midvein. Also resembles longleaf woodoats [Chasmanthium sessiliflorum (Poir.) Yates], which lacks off-center midveins and silky flowers, having tufts of spiked flowers and seeds along a slender stalk.
History and use
Introduced from Southeast Asia into FL, southern LA, southern AL, and southern GA in the early to mid-1900s. Initially for soil stabilization. Expectations for improved forage unrealized. Federal noxious weed.
TexasInvasives.org – Home
Cogon grass is a perennial, rhizomatous grass that grows from 2 to over 4 feet in height. The leaves are about an inch wide, have a prominent white midrib, and end in a sharp point. Leaf margins are finely toothed and are embedded with silica crystals. The upper surface of the leaf blade is hairy near the base; the undersurface is usually hairless. The flowers are arranged in a silvery, cylindrical, branching structure, or panicle, about 3-11 inches long and 1 1/2 inches wide.
Native Lookalikes: Currently no information available here yet, or there are no native Texas species that could be confused with Cogongrass.
Ecological Threat: Cogon grass can invade and overtake disturbed ecosystems, forming a dense mat of thatch and leaves that makes it nearly impossible for other plants to coexist. Large infestations of cogon grass can alter the normal fire regime of a fire-driven ecosystem by causing more frequent and intense fires that injure or destroy native plants. Cogon grass displaces a large variety of native plant species used by native animals (e.g., insects, mammals, and birds) as forage, host plants and shelter. Some ground-nesting species have also been known to be displaced due to the dense cover that cogon grass creates.
Biology & Spread: Cogon grass reproduces both vegetatively and from seed. A single plant can produce several thousand very small seeds that may be carried great distances by the wind. Vegetative spread of cogon grass is aided by its tough and massive rhizomes that may remain dormant for extended periods of time before sprouting. Rhizomes of cogon grass may be transported to new sites in contaminated fill dirt or by equipment used in infested areas.
History: 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.
U.S. Habitat: 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.
U.S. Nativity: Introduced to U.S.
Native Origin: Old World trop. & temp regions (Germplasm Resources Information Network); NatureServe Explorer
U.S. Present: AL, FL, LA, MS, OR, SC
Distribution in Texas: Cogon grass is distributed throughout the south and southeastern United States as far west as eastern Texas. There have been reports of cogon grass surviving as far north as Virginia, West Virginia and Maryland.