A Eurasian grass (Agropyron repens) that has whitish-yellow root stocks and has become a troublesome weed in the New World. Also called quack grass, witch grass. or quack grass Rapidly spreading grass (Agropyron repens) with flat, somewhat hairy leaves and erect flower spikes, native to Europe and introduced into other northern temperate areas for forage or erosion control. In cultivated land, it is considered a weed because of its persistence. Its long, yellowish-white rhizomes must be completely dug up to eradicate the plant because broken rhizomes generate new plants. Couch grass has been used in various home remedies in Europe, and the rhizomes have been eaten during periods of famine