Clover that is growing in a lawn can be killed either by using weed-killing chemicals or through more natural means. Good Nature Organic Lawn Care points out that clover actually offers some benefits to lawns.
Weed-control chemicals are useful for killing clover, which is one of the most common weeds in the United States. Anyone wishing to use weed-control chemicals must make sure to choose a weed-killer which will not harm the type of grass in the lawn. Clover can also be spot-treated using weed-killers appropriate for the lawn. Organic weed-killers also exist which weaken clover without harming grass, allowing the grass to outgrow the clover. Organic weed-killers work best when a lawn is well-watered.
Fertilizer also helps defeat clover. Because clover thrives in nitrogen-poor soil, the nitrogen added by fertilizing helps keep clover at bay.
Clover grows well when lawns are mowed short. Letting a lawn grow out a little bit, then mowing it to keep the grass blades at 3 inches or taller helps to kill clover.
Some homeowners or gardeners choose not to fight clover when it appears in a lawn because of the benefits it supplies. Clover roots have a symbiotic relationship with bacteria that absorb nitrogen, meaning that a lawn containing clover stays well-fertilized without the addition of chemical fertilizer. Clover also provides good shade for the soil, which in turn helps prevent other weeds from rooting. Micro-clovers allow for the benefits of clover without the little white flowers that disrupt the smooth, green look of a healthy lawn.