Clover, most commonly the white variety Trifolium repens, is a perennial, broadleaf plant often found in turfgrass. This low-growing legume is characterized by its three-leaflet structure and spreads using creeping stems called stolons that root as they grow. While some view clover as beneficial, its presence indicates poor soil conditions that favor its growth over turfgrass. Clover thrives where turfgrass struggles, outcompeting desirable species and creating an uneven appearance in a uniform lawn.
Non-Chemical Methods for Control
One immediate cultural adjustment to suppress clover involves modifying your lawn’s maintenance routine to favor grass growth. Raising the cutting deck on your mower to a height of at least three inches, and ideally between 3.5 and 4 inches, is necessary. This increased blade height allows the turfgrass to grow taller, shading the low-lying clover and blocking the sunlight it needs to thrive. By reducing light exposure, the grass gains a competitive advantage over the clover, causing it to weaken.
Proper watering practices can further stress the clover while strengthening the turfgrass root system. Instead of frequent, shallow watering, which encourages the clover’s shallow root system, deep and infrequent watering is recommended. Soak the lawn long enough for the water to penetrate four to six inches into the soil, then allow the topsoil to dry out before watering again. This encourages the turfgrass to develop deeper, more robust roots, making it more resilient and less susceptible to clover encroachment.
For small, isolated patches of clover, manual removal remains a non-toxic and effective method. Clover spreads by seed and through its surface-level stolons, so it is important to remove the entire plant, including the roots and any attached runners. Hand-pulling is easiest after a heavy rain or watering when the soil is moist. This reduces the likelihood of brittle stolons breaking off and leaving root fragments behind that can regrow.
Another non-chemical strategy for contained areas is temporary smothering, which involves completely blocking all light to the patch. Placing opaque materials like black plastic sheeting or thick cardboard over the affected area for several weeks will cause the clover to die from a lack of photosynthesis. This method is non-selective, meaning it will also kill the underlying turfgrass. Reseeding the area is required once the clover has been eradicated.
Targeted Herbicide Application
When cultural controls are insufficient to manage a widespread clover infestation, selective herbicides provide a targeted chemical solution. Since clover is a broadleaf plant, a post-emergent selective herbicide formulated to kill broadleaf weeds without harming turfgrass is necessary. Effective active ingredients commonly found in these products include 2,4-D, dicamba, and MCPP (mecoprop-p). These ingredients are often combined to increase effectiveness against clover.
These herbicides are systemic, meaning the chemical is absorbed through the clover’s leaves and transported throughout the plant, killing the roots and stolons. For the best results, application should occur when the clover is actively growing, typically in the spring or fall when temperatures are consistently moderate. Applying these products when temperatures exceed 85 degrees Fahrenheit can risk damaging the surrounding turfgrass.
Spot-treating small patches with a pump sprayer is the most precise method, minimizing chemical use and protecting the surrounding lawn. For larger infestations, a broadcast application across the entire lawn may be required. Follow the product label’s mixing ratios and application timing exactly. Always wear appropriate personal protective equipment, such as gloves and eye protection, and keep pets and people off the treated area until the spray has fully dried, which usually takes a few hours.
Long-Term Prevention Through Soil Health
Preventing clover spread involves correcting the underlying soil deficiencies that allowed it to flourish initially. Clover is a member of the legume family and hosts symbiotic Rhizobium bacteria in nodules on its roots, allowing it to perform nitrogen fixation. This process converts atmospheric nitrogen into a usable form. This gives clover an advantage in nitrogen-poor soils where turfgrass struggles to establish dense growth.
The presence of clover indicates that the soil is deficient in nitrogen, the nutrient most responsible for lush, green turfgrass growth. To shift the competitive balance in favor of the grass, a consistent, high-nitrogen fertilization program is necessary. Fertilizing with a product that has a high first number in its N-P-K ratio (Nitrogen-Phosphate-Potash) will push vigorous turf growth. This creates a dense canopy that naturally crowds out and shades the low-growing clover.
Before beginning any extensive treatment, a professional soil test should be conducted to determine the soil’s pH level and nutrient composition. Clover tolerates a wider range of pH than most turfgrasses. The test results will guide the application of lime or sulfur to adjust the pH to the optimal range for the specific turf species in the lawn. Customizing the fertilization and amendment schedule based on these readings is important.
Addressing soil compaction is another physical modification that favors turfgrass over clover. Clover tolerates compacted soil because its taproot can push through dense soil layers to access moisture, while turfgrass roots are restricted. Core aeration, a process that pulls small plugs of soil from the lawn, improves water and nutrient penetration and increases oxygen flow to the grass roots. Performing aeration and dethatching to remove excessive organic matter will create an environment where the desired turfgrass can thrive and form a dense, protective layer, making it harder for clover to take hold.