Couch grass is one of the so-called root weeds in the garden, which are particularly difficult to control. However, with a little perseverance and the right technique, the wild grass can be controlled.
Couch grass (Elymus repens) is a rhizome-forming grass of the grass family (Poaceae). The plant is found almost all over the world. In the garden, couch grass is a dreaded weed that is difficult to control. The reason: it spreads both by seeds and by underground creeping shoots. The rhizomes can grow up to one meter (40 in) per year under favorable conditions and form numerous daughter plants. They usually run horizontally in the soil at a depth of 3 to 10 centimeters (1.2 to 4 in).
From an ecological point of view, couch grass is a classic pioneer plant, as it also colonizes humus-free, sandy to clayey raw soils. Here it is initially relatively unrivaled and can conquer large areas within a few years. As soon as the first trees and shrubs spread over the area and shade the soil, the couch grass is pushed back again, since it has a high light requirement and shading severely restricts its vitality. Couchgrass is also often found in cropland. Its spread is even favored by mechanical tillage, as the rhizomes are often torn up by the tines of the cultivator and spread over the entire field.
How to fight couch grass in the garden?
If you have the wild grasses in the garden, good advice is often expensive, because just chopping and pulling out the couch grasses brings only short-term success. New blades soon sprout again from the underground rhizomes. Each new growth must be consistently removed again to slowly starve the plants. However, this method is tedious and it usually takes a whole season before the first successes are seen.
If the plants are growing in an area that is still unplanted, the rhizomes should be cleared piece by piece with a digging fork. Here, amateur gardeners with sandy soils have a clear advantage, because with loose subsoil, you can often simply pull the flat stolons out of the soil over longer distances. On clay soils, control is more difficult: here you have to be careful not to break off the rhizomes and carefully shake each short piece out of the soil.
If you have cleared a section of your garden of couch grass, you should then plant potatoes here for a year. The solanum plants shade the soil very strongly with their lush foliage and reliably suppress the new shoots from the remaining rhizome pieces.
Covering the area interspersed with couch grass is less tedious. Simply chop off the shoots, which can be up to 120 centimeters (4 ft) long, and then spread corrugated cardboard over the entire area, which can be covered with a thin layer of soil or bark mulch. The cardboard usually rots within twelve months and the couch grass suffocates under it because the shoots can no longer sprout to the surface.
If couch grass is growing in the perennial bed, a major renovation is usually in order: Dig up the perennials in fall or spring, divide them, and carefully remove the white couch grass rhizomes from the root balls. The remaining rhizomes are then cleared and the bed is then replanted with the perennial cuttings.
Fighting couch grass in the lawn
Couch grass also appears occasionally in the lawn. However, it will not bother most amateur gardeners too much. After all, it is a grass species that is hardly noticeable in combination with the lawn grasses. However, if the light-colored, relatively broad leaves are a thorn in the side of a well-kept ornamental lawn, there is no way around cutting off the areas containing couch grass with a spade. To ensure that the lawn is not too badly affected by this measure, it is advisable to first remove the sod that has been overgrown by the couch grass and pull out both the above-ground plant parts and all rhizomes by hand. After that, you should also systematically sift through the deeper soil layers with a digging fork and uproot all couch grass rhizomes. Then level the subsoil again and lightly compact it with your foot, and finally place the now couch grass sods back on top. At first, this measure sounds time-consuming, but since couch grass usually only occurs in small areas in the green carpet, it can be done relatively quickly.