White clover (Trifolium repens) is a common perennial weed that quickly spreads throughout a lawn, creating unsightly patches with its distinctive three-leaflet leaves and white flower heads. This low-growing plant spreads aggressively through above-ground runners called stolons, forming dense mats that compete with turfgrass. Removing clover without damaging the surrounding grass relies on exploiting the fundamental biological differences between the broadleaf weed and the desired turf. Selective removal methods, from physical techniques to specific herbicides, target the clover while promoting a strong, healthy grass environment that naturally resists weed invasion.
Non-Chemical Methods for Clover Control
Small or isolated patches of clover can often be managed effectively through physical and cultural control methods without chemical treatments. Manual removal is a practical first step, requiring a garden trowel to loosen the soil and remove the entire clover plant, including the roots and stolons, to prevent regrowth. This technique is most successful when the clover is caught early before it becomes widespread.
Another simple cultural method involves depriving the clover of sunlight using an opaque covering, like a plastic sheet or garbage bag, secured over the infested area. This process, which can take a few weeks, effectively smothers the low-growing plant, though it will temporarily affect the grass underneath. Adjusting the mower height to three inches or higher is also beneficial, as the taller grass blades cast shade onto the clover, limiting its access to light and hindering growth.
Concentrated horticultural vinegar can be used as a non-selective contact herbicide on clover. The acetic acid in the vinegar will dry out the leaves, but this application requires caution, as concentrated products can cause skin and eye damage and will kill any plant tissue they touch, including grass. For this reason, vinegar is best used only as a spot treatment on the clover itself, not as a broadcast spray over the lawn.
Understanding Selective Herbicides
For larger clover infestations, selective herbicides offer the most practical solution for eliminating the weed without harming the turfgrass. These products target the physiological differences between broadleaf plants, like clover, and monocots, which include common lawn grasses. The chemical compounds disrupt metabolic pathways unique to broadleaf plants, causing the clover to die while the grass remains unaffected.
The most common and effective active ingredients for clover control are combinations of compounds like 2,4-D, dicamba, and MCPP (Mecoprop). Dicamba and 2,4-D function as synthetic auxins, which are hormones that cause uncontrolled, distorted growth in the broadleaf weed, leading to its demise. These systemic herbicides are absorbed through the clover’s foliage and translocate throughout the plant, eliminating the roots to prevent regrowth.
Proper application timing is crucial for success, with the best results occurring when the clover is actively growing in the spring or early fall. Applying the herbicide when temperatures are moderate (between 45 and 90 degrees Fahrenheit) ensures the clover is metabolizing and can effectively absorb the chemical. It is recommended to wait at least two days after mowing before application, allowing the clover leaves to regrow and maximize the surface area for absorption.
Long-Term Lawn Health and Prevention
Clover’s presence often indicates that the soil is deficient in nitrogen because, as a legume, it fixes its own nitrogen from the atmosphere through a symbiotic relationship with Rhizobium bacteria. This ability gives clover a competitive advantage in nutrient-poor environments where turfgrass struggles. Therefore, the most effective long-term prevention strategy is to maintain a dense, nitrogen-rich turf that crowds out the weed.
Regular fertilization with a nitrogen-heavy product fuels the grass, promoting strong growth and making the soil inhospitable to clover. Slow-release nitrogen fertilizers are beneficial for maintaining consistent nutrient levels over time. Maintaining a mowing height of three inches or more supports a deeper grass root system and helps shade the soil surface, which discourages clover germination.
Practices such as aeration and overseeding are fundamental to prevention by improving the growing conditions for the grass. Aeration relieves soil compaction, allowing grass roots to deepen and access necessary air and nutrients. Overseeding introduces new grass seedlings to fill in any bare spots. A thick, robust lawn canopy naturally blocks sunlight from reaching the soil, preventing clover seeds from establishing a foothold.