Plants that out-compete other more desirable plants or simply invade half the garden are classed as weeds and require control. First, consider whether this can be done using non-chemical means such as digging out or suppressing with a mulch.
Where these methods are not feasible, chemical controls may need to be used. Choose a weedkiller that is most appropriate for that purpose by reading the label carefully before buying or using.
Try non-chemical control options in the first instance;
- Where practical, carefully lift out isolated specimens using a hand fork
- If the weed is widespread, rake the turf to lift stems before mowing and always use a grass-box on the mower to minimise seed dispersal
- Apply lawn fertilisers regularly to strengthen the grass, both in summer and in autumn. Begin feeding in April when growth starts again with the arrival of settled, milder weather
- Apply a single application of a proprietary spring lawn fertiliser followed at six to eight-week intervals by an application of sulphate of ammonia at 15g per sq m (½oz per sq yd); its nitrogen content encourages grass growth and acts as a deterrent to the clover
- Even distribution of sulphate of ammonia is essential, or it may scorch or burn the grass. To minimise scorch risk, bulk it out with three or four times its weight of dry sterilised soil or sharp sand. Apply only when the soil is moist and preferably in showery weather. Alternatively, apply lawn fertiliser at 30g per sq m (1oz per sq yd) in April and repeat the dressing at about six-week intervals
- Do not apply spring or summer fertilisers or sulphate of ammonia after early August. If the grass is still in poor condition in late summer and the lawn has been neglected in the past, apply a proprietary autumn lawn fertiliser in September. If, however, the grass has been regularly fed, defer further feeding until the following spring, as the use of an autumn fertiliser with its higher level of phosphorus may do the clover more good than the grass
White or Dutch clover (Trifolium repens) is relatively susceptible to dicamba, dichlorprop-P and mecoprop-P (e.g Doff Lawn Spot Weeder, Westland Resolva Lawn Weedkiller or Bayer Lawn Weedkiller) and may be eliminated after one or two applications. Lesser yellow trefoil (Trifolium dubium), however, shows strong resistance to the majority of lawn herbicides. Products containing fluroxypyr (Scotts Verdone Extra/Weedol Lawn Weedkiller, Scotts Verdone Extra/Weedol Lawn Weedkiller Ready to Use) are particularly effective at controlling clovers, including the more persistent species such as Trifolium dubium.
The other clover-like species occasionally encountered as lawn weeds, including Lotus corniculatus (birds foot trefoil), Medicago lupulina (black medick), Trifolium arvense (hare's foot) and Trifolium micranthum (slender trefoil) are similar to Trifolium dubium in their resistance to lawn weedkillers and the same control measures apply. One weedkiller (Scotts Verdone Extra/Weedol Lawn Weedkiller or Scotts Verdone Extra/Weedol Lawn Weedkiller Ready to Use), containing fluroxypyr, MCPA and clopyralid, is also listed as controlling Medicago lupulina.
Applications after August are increasingly less effective and as the majority of clovers found in lawns self-seed freely, further applications the following spring will inevitably be required.
Weedkillers often cause severe damage if applied to lawns within six months of sowing or turf-laying. However, materials containing fluroxypyr as one of their ingredients are claimed to be safe to use after only two months.
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see section 1b and c)
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers