Elymus repens aka Quackgrass

Elymus repens is a perennial grass in the Poaceae family. Gardeners know it as couch grass, quackgrass, or twitch. Its native range covers temperate Eurasia and North Africa. It is native to Britain and Ireland, too. The name Elytrigia repens refers to the same species. It grows in gardens, fields, meadows, and hedgerows. Its fast spread makes it a persistent garden weed.

Plants reach about 3.3–4.9 feet (1–1.5 m) tall. Their listed spread is 1.6–3.3 feet (0.5–1 m). Creeping rhizomes let patches spread beyond this footprint. These underground stems form a dense, pale yellow network. The flat green leaves reach 1.3 feet (0.4 m) long. Pale hairs cover the sheaths of the lower leaves. The foliage dies back each year. Upright flower spikes reach 3.9 feet (1.2 m) in late summer. Plants also make seed, which can survive for years underground.

Couch grass grows in full sun or partial shade. It accepts chalk, clay, loam, and sandy soils. Acid, neutral, and alkaline ground all suit it. It grows in moist soil and tolerates poor drainage. The RHS rates its hardiness as H6. Plants for a Future lists USDA zones 3–9. Growth starts early in spring, ahead of some nearby plants. It can reach its mature size within a year. Plants usually have few pest or disease problems.

Its main garden drawback is its strong underground spread. Dense patches compete with plants in lawns and borders. Cutting can prompt more shoots rather than curb growth. The plant needs no pruning. Rough wildlife areas offer a place to tolerate it. Caterpillars of several moths and butterflies eat its leaves. Its creeping growth has also helped bind coastal sand dunes. Other recorded uses include fodder, liquid plant feed, and dye.

Recorded edible parts include grain, rhizomes, young leaves, and shoots. The rhizomes can be cooked or dried into flour. Roasted roots have served as a coffee substitute. Young leaves and shoots have been eaten raw in spring. The roots also have a history of herbal use. Reported uses focus on kidney and urinary complaints. These uses do not establish safety for prolonged treatment. Plants for a Future warns that prolonged use may lower potassium through increased urination.