Couch grass is a perennial, strongly rhizomatous grass. The string-like runners can branch underground and reach lengths of up to 2 m. This vegetative propagation is more important than generative fruit formation. Couch grass often produces culms without inflorescences. Flowers in June. Couch grass is a common weed on arable land and grassland. It is equally at home on light mineral soils and damp clay soils. Spread is encouraged by patchy crop growth. Couch grass can be controlled on arable land by mechanical and chemical means and on grassland by early grazing and overseeding sparse patches. Although couch grass is eaten by cattle and used as hay (forage value 5), only the first growth is vigorous and yields are generally unsatisfactory. A good supply of nutrients and dry conditions encourage its spread. Couch grass seed is often included in ground cover mixes to help prevent erosion.
| Leaf | Leaf rolled in the bud, leaf sheath open (sometimes closed in lower part), hairy or glabrous. Leaf blade flat, lightly ribbed, often glaucous. Hairiness varies from light to dense. Long, claw-like auricles mostly overlapping. Ligule short and rough, straight or finely toothed. |
| Culm | Culm up to 100 cm tall, geniculately ascending. Some culms bear spikes and some have no inflorescence. |
| Inflorescence | Loosely packed two-row “true” spike approx. 20 cm long. Upright spikes with terminal spikelet. Tough spike spindle, usually 12–20 spikelets. Spikelets lie with their flat side to the spindle. Tips of glumes are awn-like. Tapered five-veined lemma with short awn. |
| Fruit | The entire spikelet with glumes is shed from the spindle. Pronounced bulge at the base of lemma contained by a furrow. Pedicel trough-like. TSW approx. 4 g. Caryopsis has a longitudinal furrow on the ventral side and the tip is finely haired. |