White clover (Trifolium repens) is a perennial broadleaf plant that many homeowners consider a weed. Clover’s ability to thrive in poor soil allows it to quickly spread and disrupt the uniform appearance of a turfgrass lawn. To eliminate this persistent plant without damaging the surrounding grass, a targeted approach using selective herbicides or specific cultural practices is necessary. The distinction between broadleaf weeds, like clover, and turfgrass is the basis for successful chemical control.
Active Ingredients That Target Clover
Selective herbicides control broadleaf weeds while leaving most turfgrass species unharmed. They exploit the biological differences between broadleaf plants and grasses. Clover is susceptible to herbicides that mimic auxins, which are natural plant growth hormones. When applied, these synthetic auxins overwhelm the clover’s system, causing uncontrolled growth that leads to plant death.
The most common and effective active ingredients for clover control are 2,4-D, MCPP (Mecoprop), Dicamba, and Triclopyr. Each ingredient targets the clover through the same mechanism but offers slightly different efficacy against various weeds, which is why they are frequently combined. These combinations, often called “three-way mixes,” ensure a broad spectrum of control against clover, dandelions, and other common lawn weeds. Triclopyr is particularly effective against creeping weeds like clover and ground ivy, making it a valuable component in these mixtures.
Dicamba and 2,4-D work systemically, meaning the chemical is absorbed through the leaves and moves throughout the entire plant, including the roots. Grasses are tolerant because they metabolize the synthetic hormones differently and possess specialized cells that prevent the collapse of their vascular system. This difference allows the herbicide to target the clover without causing significant damage to the desirable turf.
Proper Application Timing and Technique
The success of a selective herbicide application largely depends on proper timing and technique. The best time to apply post-emergent herbicides is when the clover is actively growing, which typically occurs in the spring and fall. Applying the product during this period maximizes the plant’s absorption and translocation of the chemical throughout its root system. The clover should have finished blooming to be most susceptible to the herbicide application.
Environmental conditions are a significant factor; temperatures should be moderate, ideally below 85°F, because high heat can cause the herbicide to volatilize or injure the turfgrass. It is important to apply the herbicide when rain is not expected for at least six to 24 hours, allowing the chemical sufficient time to be absorbed by the clover leaves. Applying on a calm day is also necessary to prevent the fine spray mist from drifting onto nearby ornamental plants.
Homeowners can choose between spot spraying and broadcast application. Spot spraying directly targets only the clover patches, which reduces the total amount of chemical used and minimizes exposure to the turf. Following the manufacturer’s directions for mixing and application rate is paramount. Using a non-ionic surfactant helps the mixture adhere better to the clover’s waxy leaves, improving uptake and effectiveness.
Non-Chemical Removal and Prevention
Non-chemical methods can remove clover and prevent its return. Small patches of clover can be removed manually by hand-pulling, especially when the soil is moist, which helps ensure the entire root system is extracted. However, this method is labor-intensive and best suited for minor infestations. Horticultural vinegar is sometimes used as a spot treatment, but it is non-selective and can scorch the surrounding turfgrass if applied carelessly.
The most effective long-term strategy for clover control involves improving the health of the turfgrass itself. Clover thrives in low-nitrogen soil because it is a legume that can fix atmospheric nitrogen, essentially creating its own fertilizer. Applying a slow-release, nitrogen-rich fertilizer helps the grass become denser and more vigorous, allowing it to outcompete and shade out the clover.
Cultural practices provide a competitive advantage to the grass. Mowing the lawn at a height of at least three inches shades the soil, making it difficult for clover seeds to germinate and establish. Deep, infrequent watering encourages the grass to develop a strong, deep root system that can better withstand stress and resist weed invasion. Overseeding bare patches in the fall also helps thicken the turf, eliminating open areas where clover seeds might otherwise take root.