| Cogongrass | |
|---|---|
 | |
| Imperata cylindrica inSusami, Wakayama,Japan with mature seed heads | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Clade: | Commelinids |
| Order: | Poales |
| Family: | Poaceae |
| Subfamily: | Panicoideae |
| Genus: | Imperata |
| Species: | I. cylindrica |
| Binomial name | |
| Imperata cylindrica | |
| Synonyms[2] | |
List
| |
Imperata cylindrica (commonly known ascogongrass/koʊˈɡoʊn/ orkunai grass/ˈkuːnaɪ/[1][3]) is a species ofperennial rhizomatous grass native to tropical and subtropical Asia,Micronesia,Melanesia, Australia, Africa, andSouthern Europe. It has also been introduced toLatin America, theCaribbean, and theSoutheastern United States. It is a highly flammablepyrophyte, and can spread rapidly by colonizing disturbed areas and encouraging more frequentwildfires.[4]
The species is most commonly known in English as "cogongrass" (also "cogon grass"),[3] fromSpanishcogón, from theTagalog andVisayankugon.[5] Other common names in English include kunai grass, blady grass, satintail, spear grass, sword grass, thatch grass, alang-alang, lalang grass, cotton wool grass, kura-kura,[3] and keri,[6] among other names.
Imperata cylindrica was first described byLinnaeus in 1759 under thebasionymLagurus cylindricus.[7] They were renamed by theFrenchentomologist andbotanistPalisot de Beauvois to the currentaccepted name ofImperata cylindrica.
Cogongrass grows from 0.2–3 m (1⁄2–10 ft) tall, its stalk is firm and has nodes covered with long white hairs.[8][9] Each clump that grows shares an extensiverhizome network, thebiomass of which accounts for 60% of the total biomass of the plant. They can penetrate up to 1.2 m (4 ft) deep, but0.4 m (1+1⁄2 ft) is typical in sandy soil.[8][10]
Theleaves are about 2 cm wide in average and12–80 centimetres (4+1⁄2–31+1⁄2 in) in length[9] 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.[8]
Its flowers small and gathered onpedicels 0.5–3 mm long from narrowpanicles slightly above its stalks that grow tall as high as 28 cm.[9]
The plant contains thetriterpenoidsarundoin,cylindrin andfernenol.[11]
The plant has become naturalized in theAmericas,Northern Asia,Europe andAfrica in addition to many islands and is listed as aninvasive weed in some areas. In the United States it survives best in theSoutheast (and, according to a 2003 survey, has overtaken more acreage in that region than the notoriouskudzu),[12] but has been reported to exist as far north asWest Virginia andOregon. 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 ofpH from 4.0 to 7.5. It prefers full sun but will tolerate some shade. InFlorida,I. cylindrica is found in areas where the soil has been disturbed, such as roadsides, building sites, timber harvesting areas, andborrow pits. It is able to invade both moist and dry upland pine forests. Once established it often forms densemonocultures.[13]
In addition to outcompeting species for resources, the grass also exhibitsallelopathic tendencies. The chemicals it releases as well as the dense mat of vegetation that usually accompanies a cogongrass invasion gives it an advantage over indigenous plants.[14]
It spreads both through smallseeds, which are easily carried by the wind, andrhizomes which can be transported bytilling equipment and in soil transport.
In theSoutheastern U.S., state governments have various eradication efforts in place, and deliberate propagation is prohibited by some authorities.[15] Cogongrass came to the Southeastern U.S. in the early 1900s as shipping material in crates.[16] Before it was named aninvasive species in the area, it was cultivated for fodder for livestock and erosion control.[17] It failed to prevent erosion because of how weedy it was, and animals would not eat it as fodder.[18] It is now listed as aFederal Noxious Weed in some Southeastern states[19] andArkansas.[20] InMississippi it is mostly concentrated in the south of the state.[21]
Control is typically by the use ofherbicides. Currently, the most effective herbicides used to control growth areglyphosate andimazapyr.[22] Burnoff is seldom successful since the grass burns at a high temperature, causing heat damage to trees which would ordinarily be undamaged by acontrolled burn; it also recovers from a burn quickly.Quarantine and extermination of this plant is especially difficult because cogongrass establishes root systems as deep as four feet, and regrowth can be triggered by rhizome segments as small as one inch.[14]
Cogongrass is difficult to contain mainly because it is highly adaptive to harsher environments, establishing itself on soils low in fertility. The grass can also grow on sand and clay. It is not eaten by many species of animal, further contributing to containment difficulties. The grass tends to be averse to dense shade, but reports indicate more shade-tolerant strains are developing.[23][timeframe?]
Thelegume vineMucuna pruriens is used in the countries ofBenin andVietnam as a biological control forImperata cylindrica.[24]
Cogongrass is apyrophyte. It is highly flammable, even when still apparently green,[25] particularly in tropical climates. It is not uncommon to see hillsides of cogongrass on fire.[26][27] Cogongrass depends on regular fires to spread and maintainecological dominance. Because of its density and high biomass, cogongrass provides a very high fuel load, enabling wildfires to burn faster, higher, and much hotter. This is hot enough to kill most competing plants, including trees. After a fire, cogongrass will recolonize the area using their rhizome network which was unaffected by the fire.[4][28][29][10]
It is regarded as an excellent plant forthatching the roofs of traditional homes throughout south-east Asia, and is even grown as a crop for this purpose.[6][30]
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. It is used intraditional Chinese medicine.[31]
A number ofcultivars have been selected for garden use asornamental plants, including the red-leaved 'Red Baron', also known as Japanese blood grass.
Younginflorescences and shoots may be eaten cooked, and the roots contain starch and sugars.[32]
A common expression in thePhilippines isningas kugon ('cogonbrush fire'). It is afigure of speech for quitters, specifically people who show a fervent interest in a new project but lose interest quickly, in reference to the propensity of cogongrass to catch fire and burn out quickly.[33] The concept is similar to, but distinct from,procrastination.[34]
