Cogongrass quick facts

What is cogongrass?

Cogongrass (Imperata cylindrica) is a tropical to subtropical grass that has an attractive white, plume-like inflorescence. This grass is considered to be one of the world's top ten worst weeds. In the U.S., the plant is listed federally as a noxious weed. Nevertheless, one cultivar, Japanese blood grass (Imperata cylindrica 'Rubra' or 'Red Baron'), is used as an ornamental plant.

How is cogongrass identified?

Cogongrass is a perennial plant that spreads via pale and scaly rhizomes. It can reach 1.5 meters (about 5 feet) or more in height. The leaves are yellowish green and have a midvein that is slightly off-center in the leaf blade. The spikelets have conspicuous white hairs, which gives the inflorescences a feathery, plume-like appearance.

Where did cogongrass come from?

Cogongrass is native to parts of Europe, much of Africa, and southwest Asia. Today, it has spread widely beyond its native range to suitable areas of the Eastern Hemisphere and is distributed from around the Caspian Sea south and east as far as northeast China, the Koreas, and Japan, and south as far as Australia and New Zealand.

In the Americas, cogongrass is currently found in the southeastern U.S. from Virginia to Texas, in Oregon, and in southern and western Mexico. It also grows in Hawai'i. Cogongrass reached the United States in the early 1900s, first unintentionally as packing material and later as a forage grass. 

How does cogongrass spread?

Cogongrass spreads efficiently via rhizomes (horizontally growing underground stems) and, in some regions, may also reproduce by seed.

What are the impacts of cogongrass?

Cogongrass is a weed of cultivated fields, disturbed areas (for example, roadsides), and natural areas like forests, wetlands, and savannas. Cogongrass can crowd out other plants to form monocultures (environments dominated by one type of organism) in pastures and wildlands. Cogongrass is fire-adapted and burns at high temperatures. Fire can promote the dominance of cogongrass, and cogongrass infestations can increase the risk of fire in infested areas. 

Because cogongrass is a poor forage grass, it is undesirable for grazing livestock. It can also infest cultivated fields, although cogongrass may be easier to manage in cultivated areas than in pastures and wildlands. 

How is cogongrass controlled?

No single method can be used to control cogongrass, but methods can be used in tandem to prevent its spread. The age of the grass strongly determines which control methods will be most effective. 

Tilling is a good option for younger cogongrass infestations, which have less established rhizome mats. Frequent tillage prevents the re-emergence of cogongrass seedlings.

The use of herbicides is the most common control method. Herbicides containing glyphosate can be used, although repeated use over several years is needed. So far, cogongrass does not appear to have developed resistance to the herbicides that are used to manage it.