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Lawns: weed control

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last updated Mar 27, 2014
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Clover in lawns - what is the best weedkiller to use? Credit: RHS/Advisory

One gardener’s weedy lawn is another's wildflower meadow, so decide if you really want to combat these plants. On weedy lawns, selective lawn weedkillers will usually control the weeds, but leave the grass unharmed.

What are lawn weeds? Back to top

Although the term ‘weed’ is subjective, it is usually applied to invasive plants that compete with the grass for space to grow – clover and dandelions, coarse-leaved grasses, daisies and buttercups as just some examples.

Early identification and prompt removal can alleviate large-scale problems. This can be as simple as following a yearly lawn maintenance plan. The season starts with spring and summer care but autumn care is particularly important.

Appearance Back to top

There are several ways lawn weeds are often noticed:

  • The grass may look patchy, have an uneven growth rate or simply include areas that are a different colour or texture to the rest of the lawn
  • Flowers appear in the grass. This can occur even in a closely mown lawn, but often appears when the grass is allowed to grow longer
  • Patches may remain green during a drought. Lawn weeds may perform better or worse than the lawn grasses, staying green or turning brown

Cause Back to top

Lawn weeds establish because they survive close, regular mowing. They spread by seed or creeping stems, and are usually problematic where the grass is sparse.

Control Back to top

First, consider whether you wish to control the weeds using non-chemical means, such as digging out. Where these methods are not feasible, chemical controls may be needed. Choose a weedkiller that is most appropriate for that purpose by reading the label carefully before buying or using.

Non-chemical controls

There are a number of non-chemical options to try first;

  • Feeding, aerating and scarifying will encourage the grass to be more vigorous and so make it more difficult for the weeds to compete
  • Remove rosette-type weeds, such as dandelion, daisy and plantain, with a handfork
  • Dig out weeds resistant to weedkillers in autumn; and re-turf or re-seed
  • Rake over and then mow to discourage creeping weeds such as speedwells, white clover, silverweed and sorrels
  • Apply garden lime to acid soils in the winter. Dress with lime at 50g per sq m (1½oz per sq yd) to deter weeds such as sorrels and field woodrush
  • Avoid close mowing, particularly with parsley piert and pearlwort, as this can weaken the grass and allow the weeds in

Chemical controls

Lawn weedkillers may be needed where many weeds have established. When buying a lawn weedkiller, check the label to find out if it will work on the weeds in your turf.

  • Apply a weedkiller in a spring and summer, when the grass and weeds are growing vigorously
  • Read the instructions before you begin. It is important to follow them and apply the weedkiller as stated – this will ensure effective results and your safety
  • Choose a product that is easy to apply. Lawn weedkillers are available to spray on, apply with watering can and dribble bar, and less frequently as granules that are scattered on the surface
  • For spot treatment, apply ready-to-use sprays
  • Only use with a combined mosskiller where moss is a problem
  • Most lawn weeds are killed by weedkiller application, some by a single treatment, but others requiring two or three applications at four to six week intervals

New lawns are often severely damaged by weedkillers if applied to lawns within six months of sowing or turf-laying. However, products containing fluroxypyr (Scotts Verdone Extra) as one of their ingredients are claimed to be safe to use after only two months.

Download

Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1b, c and d, and 2a)

Links

Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers

Composting treated clippings Back to top

What can you do with lawn clippings after applying a weedkiller?

  • Do not put the first clippings after application on the compost heap
  • Products containing clopyralid can be more persistent. Again, the first clippings should not be composted and the next three mowings should be used as a mulch. After at least nine months, they are suitable for composting
  • To avoid contamination of compost, allow the short clippings to remain on the surface of the lawn

Quick facts

Common name Various
Botanical name Various
Areas affected Lawns
Main causes Weeds with creeping stems or seeds
Timing Treat from spring to early summer or dig out in autumn
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