Couch grass

Couch grass is a vigorous, spreading perennial grass, which becomes a serious weed problem wherever it colonises. Once it gets a hold in your garden, it can quickly spread everywhere.

It looks pretty much like any other tufted grass, producing large, coarse clumps – making it unsuitable as a lawn grass. But the main problem is underground, where its mainly white, creeping, perennial “roots” – actually underground stems or rhizomes – grow rampantly through the soil to form thick mats of roots. These produce new clumps of leaves wherever they go. As a result, couch grass colonises large areas of ground. Luckily, it rarely produces seeds!

One of the main problems arises when the extensive network of roots becomes entwined with the roots of wanted plants, as they are difficult to remove and control.
Couch grass will quickly and easily spread from lawns to adjacent borders.

• Beds
• Borders
• Lawns
• Gravel paths
• Between paving slabs
• Waste or uncultivated ground

In early spring, thin grass leaves begin to appear through the soil, quickly growing into a large clump – both height and spread. In summer, it produces large flower heads.

It may remain green overwinter or die down to its roots in late autumn.

As with most perennial weeds, never allow couch grass to become established. This will make it more difficult to fully control. Early identification and eradication is very important.

Start by digging out as much of the couch grass as possible, including the white, creeping roots. Be rigorous as the roots easily break into smaller pieces and even a tiny piece left in the ground can re-grow into a new plant. A fork and hand fork are usually better tools than a spade and trowel, which will cut the roots into smaller pieces. Check a week or so later for signs of re-growth and dig this up as soon as possible too.

Covering the soil with weed-control membrane (landscape fabric) or thick black polythene to exclude light and starve the roots is unlikely to control couch grass. The roots have sharp tips, which will easily pierce plastic – and most other obstacles in their way.

If the roots are growing among established plants, you may have to lift these when dormant, from autumn to the end of winter, and tease out all the couch grass roots. Then replant in clean soil or pot them up for planting out later.

Regular hoeing, as soon as new growth appears above the ground, may weaken the plant – but this has to be carried out religiously, regularly and will take many years to be effective.

If it’s a problem in lawns, there is very little you can do to control it. Instead you should kill the lawn and make sure to dig out or otherwise kill any remaining roots before re-seeding or re-turfing.

You may unknowingly introduce couch grass into your garden when buying topsoil or manure, or in the rootballs of new plants. So be vigilant when buying these.

There are a number of weed control options available to treat sow thistles. In addition to traditional weedkillers there are now also a range of more natural alternatives.

Contact weedkillers will burn and kill the foliage, but will have no effect on the roots, which will continue to grow, produce new leafy growth and spread further.

For best results, spray with a systemic weedkiller. A systemic weedkiller, which is absorbed by the leaves, then moves down to the roots to kill them.

To ensure the weedkiller works effectively:

• Spray the leaves when the couch grass is growing actively; this is mainly from March/April to October/early November.
• The larger the leaf area present, the greater the amount of weedkiller that can be absorbed and move down to the roots. So don’t bother spraying when the growth first emerges through the soil – wait until the leaves are at least 12.5-15cm (5-6in) long.
• Use a fine spray to thoroughly coat the leaves in small droplets.
• During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to be absorbed. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.
• One application of weedkiller is unlikely to kill all the couch grass. You may need to spray once, allow the couch grass to die down, and then spray any regrowth again. Three or more applications a year, over a couple of years, may be needed to completely kill it, depending on how extensive the root system is.

Most contact weedkillers are total weedkillers – that is they will damage or kill any plants whose leaves they are sprayed on. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect plants by covering with polythene or similar when spraying.

Use weedkillers safely. Always read the label and product information before use.

As couch grass spreads by its underground roots, it may be coming into your garden from a neighbouring garden or surrounding waste ground. Unless you can stop this source, it will just keep coming back. However, as the pointed tips of the roots can pierce plastic barriers for instance, you may have to insert barriers of corrugated iron, paving slabs or similar.

• Spade
• Fork
• Hand fork
• Systemic weedkillers