Clover is a major headache for many lawn owners. During the dry days of midsummer the bright green patches stand out against the dull and pale grass. This patchy effect is an eyesore, and control was difficult until the discovery of the newer-type selective weedkillers.
The clovers you are most likely to see are white clover (Trifolium repens) and the smaller yellow-flowering species known as lesser trefoil. As with all clovers, they are encouraged by both water shortage and nitrogen shortage. So wherever clover is a problem you should feed with a nitrogen-rich fertilizer every spring – never use a phosphate- or potash-rich fertilizer at the start of the season.