Rottboellia cochinchinensis (itch grass).
Abstract The erect, profusely tillering annual grass R. cochinchinensis grows up to a height of 4 m or more and is extremely competitive with annual crops, readily invading disturbed sites along roads and railways. Commonly known as itchgrass, it has brace roots near the base of the plant, a cylindrical spikelet seedhead and siliceous hairs on the leaf sheath that can penetrate and irritate the skin. Individual plants produce 2000 to 16,000 seeds that are shed as soon as they mature. A native of Indo-China, it is naturalised throughout the tropics of Asia, and is found in north-eastern Australia and savannah zones of Africa. It has been introduced into tropical America, as a potential pasture grass in the USA in the early 1900s and since the 1960s has been spread widely by contaminated rice seed, agricultural equipment and along transport routes in Central and South America, the Caribbean, and in the Gulf Coast region of the USA. An aggressive, significant weed in more than 40 countries, R. cochinchinensis is listed as a Federal Noxious Weed in the USA, and is suggested by Vibrans (2009) to be possibly the most harmful invasive plant in Mexico.