How to Successfully Tackle Couch Grass
Couch grass is one of the hardest creeping weeds to deal with in the garden. With a little endurance and the right technique, you can still get this wild grass under control.
Couch grass (Elymus repens) is a rhizome-forming grass from the Poaceae family. This plant is found almost everywhere in the world. In the garden, it is a feared weed that is difficult to tackle. Why? It spreads via seeds as well as via creeping underground shoots. The rhizomes can grow up to 3.3 feet in one year if the conditions are right, forming countless additional plants. They generally grow horizontally in the ground, roughly 1.18 to 3.94 inches deep.
From an ecological perspective, couch grass is a classic pioneer plant as it settles in humus-free, sandy to loamy crude soils. Here, it has relatively little competition so can conquer large areas in just a few years. As soon as the first woody plants settle in the space, casting shade on the ground, the couch grass is suppressed as it requires a lot of light. Shade drastically impacts its vitality. Couch grass is also often found on arable land. Its spread is actually encouraged by mechanical soil preparation, as the rhizome is often shredded by the cultivator’s prongs and distributed across the whole field.
Common couch grass is one of the most persistent weeds because it forms underground creeping shoots. To control it effectively, uproot the rhizomes piece by piece with a digging fork. This will prevent couch grass from resprouting. Alternatively, you can cover the area interspersed with couch grass: first chop off the shoots, lay out corrugated cardboard and cover it with bark mulch, for example.
How can you get rid of couch grass in the garden?
If you have these wild grasses in your garden, good advice is invaluable as simply cutting or ripping the couch grass up will only bring short-term success. New shoots will soon spring forth from the underground rhizomes. All new growth must be thoroughly removed so that the plant slowly starves. This method is long-winded, usually taking a whole season until you see any success.
If the plants are growing on land that has not yet been planted, the rhizomes should be dug up piece by piece with a gardening fork. Here, hobbyists with sandy soil have a clear advantage, as looser substrate makes it easier to simply pull the horizontal offshoots out of the ground in long pieces. Loamy soil makes this task more difficult: you must make sure that you do not tear the rhizome, carefully shaking each piece out of the ground.
Once you have freed a section of your garden from couch grass, plant potatoes in it for one year. This nightshade causes intense ground shade thanks to its foliage, reliably suppressing any new shoots from any remaining rhizome pieces in the soil. An easier option is simply covering the area affected by couch grass. Cut the shoots, which can reach up to 4 feet in height, and spread flattened cardboard over the area, followed by a thin layer of soil or bark mulch to hide it. The cardboard will generally rot within twelve months and the couch grass will suffocate underneath as the shoots cannot make it through to the surface.
If the couch grass is growing in a perennial bed, you’ll need to undertake more significant renovations: in spring or fall, dig your shrubs out, divide them and remove the white couch grass rhizomes from the root balls carefully. Afterwards, any remaining rhizomes must be removed and the bed repopulated with the divided shrubs.
Tackling couch grass on a lawn
Couch grass also occasionally appears on lawns. Most hobby gardeners aren’t bothered by this too much – after all, it’s still a kind of grass and doesn’t stand out too much from the other grasses on the lawn. But if the light, relatively broad blades of this grass are an aesthetic thorn in your side, then there’s no other option than to dig up all areas impacted by the couch grass with a spade. To avoid excessively ruining the lawn in doing so, it’s advisable to first remove the sod from the areas affected by couch grass, then remove all above-ground parts of the plants as well as all rhizomes by hand. Afterwards, use a gardening fork to systematically sieve through the deeper layers of soil and pull up all couch grass rhizomes. Finally, level off the ground and use your foot to lightly press down the soil before replacing the sod that is now free from couch grass. This approach may sound elaborate – but as couch grass is generally only found in small patches of lawn, it is relatively quick to complete.
Treating couch grass with herbicides
We’ve included this method here for the purpose of completeness but we generally advise against the use of chemical weedkillers in the garden. It is possible to tackle this weed with systemic total herbicides. But using it in flower beds is tedious: you must be very careful to not spray the chemical onto your plants, as the herbicide does not differentiate between good and bad. It works best if you use it in dry, warm weather: the better the plants are growing, the more of the chemical they will absorb. It only begins to work once in the plant, killing it and its rhizomes.