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Imperata cylindrica

Imperata cylindrica is a species of grass in the genus Imperata. It is placed in the subfamily Panicoideae, supertribe Andropogonodae, tribe Andropogoneae.

It is a perennial rhizomatous grass native to east and southeast Asia, India, Micronesia and Australia. It grows from 0.6-3 m (2-10 feet) tall. The leaves are about 2 cm wide near the base of the plant and narrow to a sharp point at the top; the margins are finely toothed and are embedded with sharp silica crystals. The main vein is a lighter colour than the rest of the leaf and tends to be nearer to one side of the leaf. The upper surface is hairy near the base of the plant while the underside is usually hairless. Roots are up to 1.2 meters deep, but 0.4 m is typical in sandy soil.

Common names include speargrass (Nigeria), blady grass (Australia), alang-alang, lalang (Malaysia), gi (Fiji), ngi, paille de dys, paillotte, impérata cylindrique, impérate, satintail, kasoring (Palau), cotton wool grass, cotranh (Viet Nam), illuk (Sri Lanka), yakha (Laos), kunai (New Guinea), silver spike (southern Africa), Cogon Grass (United States) and Bai Mao Gen (China).

Cultivation and uses

It is used for thatching the roofs of traditional homes in Papua New Guinea.

It is planted extensively for ground cover and soil stabilization near beach areas and other areas subject to erosion. Other uses include paper-making, thatching and weaving into mats and bags. However, its most common usefulness may be seen in its medicinal properties which include astringent, febrifuge, diuretic, tonic and styptic action. It is used in traditional Chinese medicine.

A number of cultivars have been selected for garden use as ornamental plants, including the red-leaved 'Red Baron' (also known as Japanese blood grass).

Young inflorescences and shoots may be eaten cooked, and the roots contain starch and sugars and are therefore easy to chew.

Weed problems

The plant has become naturalized in the Americas, Northern Asia, Europe and Africa in addition to many islands and is listed as an invasive weed in some areas. In the U.S. it survives best in the southeast, but has been reported to exist as far north as West Virginia and Oregon. Worldwide it has been observed from 45°N to 45°S. It grows on wet lands, dry lands, areas of high salinity, organic soils, clay soils and sandy soils of pH from 4.0 to 7.5. It prefers full sun but will tolerate some shade.

It spread both through small seeds, which are easily carried by the wind, and rhizomes which can be transported by tilling equipment and in soil transport.

In the Southeastern United States, state governments have various eradication efforts in place, and deliberate propagation is prohibited by some authorities . Control is typically by the use of herbicides. Burnoff is seldom successful since the grass burns quite hot causing heat damage to trees which would ordinarily be undamaged by a controlled burn and recovers from a burn quickly.

The legume vine Mucuna pruriens is used in the countries of Benin and Vietnam as a biological control for Imperata cylindrica.

Flammability

Anecdotal and empirical evidence suggests that types of this grass are quite flammable even when apparently green - particularly in Papua New Guinea climates. It is not uncommon to see hillsides of "Kunai" on fire.