Weed of the week QUACKGRASS Elytrigia repens

QUACKGRASS Elytrigia repens

Other common names include Couch grass, scutch grass, twitch grass

Appearance of Couch Grass

• Couch grass is a common and invasive garden weed. It is a perennial grass which rapidly spreads by rhizomes (underground stems). Root system – The slender, extensively spreading rhizomes (horizontal underground stems) are white to pale yellow, with brownish sheaths at the joints (nodes), giving them a scaly appearance. Tips of the rhizomes are sharply pointed. Rhizomes can grow 3 to 11 feet long, and form a dense mat. Most rhizomes are found within 4 to 6 below the soil. Fibrous roots are produced at the nodes.
• Stems – Stems are erect, smooth, round and unbranched. They can grow 1 to 4 feet tall and, like most grasses, are hollow.
• Leaves – Leaves are rolled in the bud. The leaf blade (free part of the leaf) is dull grayish-green (sometimes dark green), thin, flat and finely pointed. Blades are finely ribbed on upper and lower surfaces, and measure 1 1/2 to 8 inches long (sometimes up to 12 inches) and 1/8 to 1/4 inch wide (sometimes up to 1/2 inch). The upper blade surface and margins are typically rough or slightly hairy, and the lower surface is smooth. The base of the blade is often lighter in color. The leaf sheath (part of the leaf surrounding the stem) is round and short, with overlapping margins. Lower sheaths are usually hairy, while the upper sheaths are smooth. The ligule (projection inside on the top of the sheath) is membranous and very short (1/50 to 1/25 inch long). A pair of whitish-green, brownish or reddish, narrow, claw-like appendages (auricles) clasp the stem at the junction between the leaf blade and sheath.
• Flowers – Flowers are arranged in a long, slender, unbranched spike (2 to 10 inches), resembling a slender head of wheat. The yellow-brown seeds (1/5 to 1/3 inch long) are elongated toward the tip, tapering to a blunt base, and topped with a ring of hairs. Seeds of couch grass s germinate in early spring, and flowering occurs from late May to September. Flowers are wind-pollinated and relatively self-sterile. One  plant can produce up to 400 seeds per season, but most plants produce fewer than 50 seeds. Seeds are short-lived, and are reported to lose viability within 4 years. Seeds have been found to remain viable after passing through the digestive tracts of horses, cows and sheep, but not after passing through pigs.

Distribution

Couch grass has become naturalised throughout much of the world, and is often listed as an invasive weed. Interference of this species with crops can cause yield reductions (up to 85% in corn) and can also result in delayed corn maturity. It is an alternate food source for several insect and disease pests of grain, such as the cereal leaf beetle (Oulema melanopa) and bromegrass mosaic virus. According to a botanical publication from 1672, it was introduced into New England by the colonists for forage. Quackgrass is typically found in crop fields, roadsides, river banks, lawns, waste places and abandoned fields. It is often used for hay and pasture. This species can grow in a variety of soil types, and has a high tolerance for drought and salinity. It prefers neutral to alkaline soils.

The Problems with Couch Grass

Couch grass or twitch grass (Elymus repens) is an old enemy for many gardeners. Its wiry, underground stems and creeping shoots pop up around garden plants and before long can take over a bed. As a perennial weed thorough killing or eradication of the roots is necessary.

The network of rhizomes become entangled in clumps of herbaceous perennials and among shrubs and fruit bushes causing great problems, as they are difficult to remove. Couch can easily spread from infested lawns into adjacent borders.

Couch is usually spread from garden to garden unwittingly when small sections of rhizomes become hidden among the roots of plants or in manures or soil.

Regular chopping of rhizomes through cultivation can be an effective way of controlling quackgrass infestations.. It is very difficult to remove from garden environments, as the thin rhizomes become entangled among the roots of shrubs and perennials, and each severed piece of  rhizome can develop into a new plant. Research has found that 30% of 1/8 inch fragments of quackgrass rhizomes were capable of producing aerial shoots It may be possible to loosen the earth around the plant, and carefully pull out the complete rhizome. This is best done in the spring, when disturbed plants can recover. Another method is to dig deep into the ground in order to remove as much of the grass as possible. The area should then be covered with a thick layer of woodchips. To further prevent re-growth cardboard can be placed underneath the woodchips. The long, white rhizomes will, however, dry out and die if left on the surface. Some herbicides will also control it. The growth of rhizomes of Elymus repens (L.) Gould (couch grass) from single-node fragments on plots sown with six perennial grasses was reduced by a factor of 10, compared with initially bare plots. The location of shoot complexes of E. repens after three seasons indicated that Arrhenatherum elatius and, to lesser extents, Agrostis stolonifera or Dactylis glomerata, prevented couch growth more than Holcus lanatus or Poa trivialis. Strips of sown grass at the edge of arable fields may therefore reduce the spread of couch grass into adjacent crops. Fertiliser application of 32 kg N ha⁻¹ doubled the amount of couch rhizome. Mefluidide and paclobutrazol, plant growth regulators which might be used to manage sown grass, had minor effects on rhizome structure. D. glomerata did not spread from where it was sown and was largely uninvaded by other species. The herbicide, N-phosphonomethyl glycine (glyphosate), is readily absorbed by the foliage and translocated in the phloem of couch grass. Despite the reduction in growth in plots where perennial grasses coexist there is no herbicide that will control couch without killing different grass species around the plant.

Ecological relevance of Couch Grass

The foliage is an important forage grass for many grazing mammals The seeds are eaten by several species of grassland birds, particularly buntings and finches. The caterpillars of some Lepidoptera use it as a foodplant, e.g. the Essex Skipper (Thymelicus lineola).

Uses of Couch Grass

Couch grass has valuable uses. It remains green all year round and can make good forage and hay. Total crude protein content is comparable to timothy (Phleum pratense). Nitrogen levels in couch grass are high enough, without reaching toxic levels, to be appropriate for cattle feed, although biomass productivity and palatability are generally low. Couch grass can be used to prevent soil erosion, and it is effective in removing nutrients from wastewater effluent when sprayed on soil.

The dried rhizomes of couch grass were broken up and used as incense in mediaeval Northern Europe where other resin-based types of incense were unavailable.

Medicinal uses

Couch grass it valued by herbalists for its mucilage rich rhizome. rhizomes have been used in the traditional Austrian medicine against fever, internally as a tea, syrup, or cold maceration in water, or externally applied as a crude drug.

A tea made from the roots is useful for treating urinary infections because of the herb’s broad antibiotic, and diuretic properties. One of the chemical constituents, agropyrone, has been shown to have strong antibiotic properties. Couch grass tea will also soothe and coat an inflamed sore throat, and helps clear phlegm. The herb contains mucilage that helps to clear congestion while it coats the throat. Other sources report that it has been used to treat gout, rheumatic diseases and chronic skin conditions. For all of these remedies there is a lack of clinical studies to support its efficacy.

Folklore

Couch grass is reputed to have been used in folk magic and the occult. The ‘power’ comes from the fact it has an irritating quality. This irritation is believed to be used to cause discomfort or pain to ones enemies as well as to shake up couples.