Once clover gets established in your lawn, it can be difficult to remove. This perennial weed thrives in most soil conditions, although it is more persistent in clay and silt soils in humid and irrigated areas. Although you shouldn't expect to eradicate this weed in a weekend, with proper lawn maintenance and fertilization you can have a clover-free lawn.
Culprit: Low Nitrogen
Clover, like any weed in your lawn, is an indication of deeper issues. This weed thrives in soils with low nitrogen levels or high phosphorus levels or a combination of the two. Your first plan of attack is to correct the issue. Start by applying low-phosphorus -- or zero-phosphorus, high-nitrogen fertilizer to your lawn at the recommended rate for your turf grass. Additional nitrogen can be added to the soil by allowing grass clippings to remain on the lawn.
Natural, Organic Solution
Organic corn gluten meal works as both a fertilizer and a herbicide when it's applied to a lawn filled with clover. This natural product must be applied in the spring because it works by preventing the germination of clover seeds. As the corn gluten meal decomposes, it will naturally add nitrogen to your soil. Timing is critical, though, when using this product because it must be applied early enough in the spring to be on the soil before the seeds germinate.
Options to Consider
If the clover has only invaded a small area of your lawn, try hand-pulling the weed. Although it may need repetition, it is an effective method of eradication. For larger areas, use a post-emergent herbicide to control both annual and perennial clovers. The best herbicide to use depends on the species of your turf grass. Herbicides containing mecoprop and dicamba work well on warm-season grasses, while any herbicide designed to control clover will work on cool-season grass.
Maintenance: Best Defense
Although weeds occasionally invade even the best kept lawns, they are not a serious problem when proper lawn maintenance is followed. A healthy stand of grass can crowd out and create a shade canopy where clover and other weeds will not thrive. To encourage healthy grass, mow it at the recommended height and never remove more than one-third of the grass blade in any cutting. Water your lawn infrequently but deeply and never overwater, because this can wash away nitrogen, potentially giving clover a foothold in your lawn.