T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Elymus repens (Couch)

Kingdom:   Plantae
(unranked):         Angiosperms
(unranked):         Monocots
(unranked):         Commelinids
Order:        Poales
Family:       Poaceae
Genus:       Elymus
Species:     E. repens
Binomial name: Elymus repens
Synonym:     Agropyron repens, Elytrigia repens, Triticum repens, Elytrigia vaillantiana, Triticum repens, Triticum vaillantianum.
Common names: Couch, Couch grass, common couch, Twitch, Quick grass, Quitch grass, Dog grass, Quackgrass, Medusa’s head, Quackgrass rye, Quackgrass grass, Scutch grass, Witchgrass.

Elytrigia repens (Couch) is a very common, invasive, perennial, rhizomatous species of grass native to most of Europe, Asia, the Arctic biome, and northwest Africa.
Couch’s stems are green to whitish, erect to decumbent and can grow to 0.9 m tall. The leaf blades are soft and relatively flat, 3-10 mm wide, dull and mostly dark green, sometimes glaucous and are 15-40 cm long. On the lower leaves, sheaths are often strongly hairy, on upper leaves smooth or slightly soft-hairy.
The flower spikes are 10-30 cm long and have 3-8 florets per spikelet. Seeds are enclosed in the glumes, forming a spool-shaped unit, broadest below the middle. The caryopsis is usually 4-5 mm long.
Couch’s rhizomes are a pale yellow or straw-coloured with internodes from 2-8 cm in length and about 3 mm in diameter. The rhizomes usually creep between the soil surface and a depth of 5-10 cm, or up to 20 cm in loose soil. Rhizomes may reach lengths of more than 1 m under favourable growth conditions. Fibrous roots develop from their nodes.
Couch occurs in pastures, gardens, roadsides, and other disturbed open areas and is one of the most troublesome rhizomatous weeds in flower gardens and crops. Its wiry, creeping underground stems send up around the garden. It is a real problem weed because it regrows rapidly following ground disturbance because regrowth occurs from the rhizomes left in the soil.
The best way of differentiating couch from most other species of grasses is that it has no runners above ground and where the leaf blade joins the sheath, there are two small pointed flaps of tissue called auricles.  Ryegrass has the same auricles.

The rhizomes

The two small pointed flaps of tissue called auricles.

The flowers

The seed heads

A diagram of the parts of Elymus repens. The graphic will enlarge on clicking.

A video on Elymus repens (which is also called Quackgrass).

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/