Clovers

(Trifolium, Lotus corniculatus, Medicago) There are several clovers that are regarded as garden weeds. While they can grow anywhere in the garden, most become a real problem when growing in the lawn.

What are clovers?

There are several clovers that are regarded as garden weeds. These include white clover (Trifolium repens), red clover (Trifolium pratense), birds foot trefoil (Lotus corniculatus) and black medick (Medicago lupulina).

Clovers are perennial plants that will grow in just about any part of the garden, often in soils that are low innitrogen. They usually become more of a problem when they establish in the lawn – their low-growing leaves covering and smothering the surrounding grass, causing bare patches. In lawns, they can be very difficult to control.

These evergreens remain throughout the year and each plant is capable of producing numerous seeds. These can remain dormant in the ground for several years. And as “One year’s seeding means seven years weeding”, allowing plants to flower and produce seeds, means several years of trying to control and remove them.

Where do they grow?

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

Appearance

All these clovers have the typical clover trifoliate (three-leaved, three leaflets) foliage. This is generally low growing, hugging the ground or wherever it is growing.

White clover has relatively large leaves, an open, sprawling habit and white or whitish flowers, often with a tinge of pink or cream, or sometimes pink flowers.

Red clover is taller growing, variable in size getting up to 80cm (32in) high. The flowers are deep pink to red.

Bird’s-foot trefoil can grow up to 20cm (8in), with spreading, sprawling stems and yellow and orange flowers.

Black medick can grow up to 45cm (18in), but is mainly low growing with spreading, sprawling stems, bunches of yellow flowers and black seedpods.

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How to control clovers

As with most perennial weeds, don’t allow clovers to become established, and certainly don’t allow them to flower and produce seeds. This will make it more difficult, and more time consuming, to fully control. Early identification and eradication is important to stop them taking over the garden.

Natural control

Digging out the plants is a relatively quick – although not necessarily easy – way of getting rid of most clovers. A fork and hand fork are usually better tools than a spade and trowel.

Regularly hoeing seedlings and young plants as soon as you see them is the quickest and easiest method of control. The aim of hoeing is to sever the weed stems at or just below ground level, cutting the top growth from its roots. A sharp hoe blade will make this even quicker and easier, so always sharpen the hoe blade before using it. Hoeing on a warm and/or windy day will mean plants quickly dehydrate and die.

Digging out the plants when they are more established is more time consuming and more difficult – especially where they’re growing among wanted plants.

Flame guns and weeders that use an electric current are also effective in some locations.

Covering bare soil with weed-control membrane (landscape fabric) or even thick black polythene will exclude light and prevent seeds germinating. As will mulching the soil with organic matter, such as a bark mulch. For mulches to work properly, they need to be a minimum of 5cm (2in) thick, but 7.5cm (3in) deep works better.

In lawns, clovers are pretty difficult to dig out, especially once they’ve started spreading. Regular mowing may weaken the plants, although those with sprawling stems usually grow too low and are missed by the mower blade. Raking before mowing to raise the stems up to the blade may improve this. Don’t compost the clippings.

As clovers are legumes and produce their own nitrogen, they grow more prolifically in poor soils. Regular feeding with a lawn fertiliser will help make conditions less suitable for clover growth.

As clovers are more drought resistant than grass, and proliferate in dry conditions, watering the lawn during prolonged dry weather will help the grass to continue to grow and out-compete the clover.

Weedkillers

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

Any weedkiller can be used to control and kill clovers in beds, borders, waste ground and on paths. Those marketed as “fast acting” are contact weedkillers – killing or damaging the plant tissue they are sprayed onto or make contact with. These tend to be based on “naturally-occurring” active ingredients, such as acetic acid and natural fatty acids.

Systemic weedkillers, that also kill the roots can also be used.

To ensure the weedkiller works effectively:

Spray the leaves when the clovers are growing actively; this is mainly from March/April to September/October. Contact weedkillers will have some effect if used during the colder weather in winter.
The larger the leaf area present, the greater the amount of weedkiller that can be absorbed. So don’t bother spraying when the growth first emerges through the soil – wait until the leaves grow larger.
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.
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.

In lawns, spray plants with a good lawn weedkiller. Not all weedkillers are as effective as others, so choose those with three or four active ingredients. Make sure the lawn is well fed and not cut too short to help the grass out-compete clovers and other lawn weeds.

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

Prevention

Don’t allow plants to flower and set seed. Although this is pretty easy in your garden, it’s more difficult to stop the seeds blowing in from a neighbour’s garden, any surrounding fields and waste ground and even further afield.