Federal Noxious Weed Disseminules of the U.S.

Imperata cylindrica P. Beauv.

Family: Poaceae,  Tribe: Andropogoneae

Common names:  cogongrass, satintail, blady grass

Disseminule:  Spikelet; disarticulation below glumes.

Description

Spikelets terete, 2.2–6 mm long (excluding callus hairs), of one fertile floret and one basal sterile lemma. Spikelet callus with silky hairs 8–16 mm long. Glumes 2.6–5.5 mm long lanceolate, pointed, as long as spikelet. Sterile lemma half as long as spikelet (1.4–4.5 mm long). Fertile lemma shorter than sterile lemma, hyaline. Styles 0.5–3.4 mm long, persisting, at least in part. Caryopsis elliptic or lanceolate.

Identification considerations

Because of its wide geographic distribution, this species exhibits much morphological variability. A number of varieties have been named, some based on geographic region.

Imperata cylindrica is often confused with Imperata brasiliensis Trin.

Distinguishing characters:

Imperata brasiliensis: 2 bracts within glumes, rarely 3; 1 stamen in flower, filament dilated at base; styles 1.1–4.7 mm long

Imperata cylindrica: 3 bracts within glumes; 2 stamens in flower, filaments not dilated at base; styles 0.5–3.4 mm long

Molecular diagnostic tools have also been used to distinguish these species.

Distribution

Throughout the Eastern Hemisphere including the Pacific Islands, in tropical and warm-temperate latitudes, and in South America: Argentina, Bolivia, Chile, Colombia, Peru, Uruguay and Venezuela; Central America; and United States.

Habitat

Wide range of habitats, from dry sand dunes to waterlogged marshes and at elevations from sea level to 2700 m. Can be a troublesome weed in cultivated areas and wastelands, as well as in native ecosystems.

General information

Imperata cylindrica is a tufted, perennial grass up to 1.5 m tall. It is a prolific seed-producer and also reproduces vegetately via hard, creeping rhizomes. Found on all continents, it is known as one of the ten worst world weeds, affecting many crops, particularly in southern and eastern Asia. This weed is a serious problem in rubber plantations in Asia, reducing rubber tree growth by 96%. Similarly, the weed significantly reduces teak tree growth, cassava yield and yam production. It is an aggressive, well-adapted weed, able to thrive in poor soils and difficult to eradicate because of its rhizomes. Great expanses of I. cylindrica develop because of the abandonment of fields resulting from its initial infestation. The mature plant has long been used as thatching, packaging material, and for rope and mat products. Although the mature grass is coarse, new growth can be used for forage. In fact, cogongrass was introduced to southeastern U.S. in the early 1900s as a potential forage crop.