Couch, scutch or twitch grass looks like just a tuft of any grass, but underneath the ground the roots spread quickly to colonise borders. Once these roots intermingle with ornamental plants they can smother the plants and become difficult to eradicate.
Identifying couch grass
Elymus repens is a common and invasive garden weed. It rapidly spreads by rhizomes or underground stems. From their tips, new shoots are produced in spring and autumn that quickly produce tufts of leaves and more rhizomes. These become entangled in clumps of herbaceous perennials and among shrubs and fruit bushes causing great problems, as they are difficult to remove.
Cultural control
Digging out couch is possible, but it is easy to leave behind small sections of rhizome in the ground. These quickly re-grow and need to be removed before they form a new network of underground stems, so perpetuating the problem.
Chemical control
Late summer treatments are more effective than those done early in the season, but try to avoid drought conditions, as results can be disappointing. Glyphosate-based weedkillers are very effective and, if correctly applied, should kill out even heavy infestations of couch in one application. But as these products are not selective, care is needed to prevent spray landing or drifting on to other cultivated plants and causing damage. Protect them with polythene while spraying and remove only once it has dried. Alternatively, an aerosol-formulation weedkiller (Advanced Glyphosate Spot Weeder for Beds & Borders) can be sprayed on more accurately.
In heavily couch-infested areas, it may be better to dig up cultivated plants, carefully tease out any couch grass roots that may be in the rootball and relocate them temporarily while treatment takes place. It is unnecessary to remove bulbs that have died back and no part of the plant is visible above ground.
The grass should die back within three weeks; but treat any re-growth as soon as possible. Do not cultivate the soil until the grass has been completely killed.