Clover, a member of the legume family, is a popular natural groundcover used to improve soil health and suppress unwanted plant growth. Unlike grasses, it fixes atmospheric nitrogen into the soil, reducing the need for synthetic fertilizers. Its rapid growth and dense coverage make clover an effective and environmentally friendly method for weed management.
Mechanisms of Weed Suppression
Clover suppresses weeds primarily through physical competition for light and space. Its dense, low-growing canopy, especially in varieties like white clover, intercepts sunlight before it reaches the soil surface. This shading effect prevents the germination of small-seeded annual weeds that require light to sprout.
The plant’s extensive root system also plays a significant role. Clover roots compete aggressively with weed roots for limited resources like water and soil nutrients. This competition slows the growth of new weed seedlings, preventing them from becoming dominant.
Some clover species, such as crimson clover, also exhibit allelopathy—the release of biochemical compounds that inhibit the growth of nearby plants. While secondary to physical mechanisms, this chemical suppression provides an extra layer of defense against certain weed species. These compounds are often released as the clover residue breaks down, maintaining a weed-suppressing environment.
Selecting the Best Clover Varieties
Choosing the right clover variety depends on the desired growth habit and the duration of weed control needed. For long-term, dense weed control in lawns or permanent groundcover, White Clover (Trifolium repens) is the most common choice. This perennial variety spreads via horizontal stems, called stolons, which root as they creep along the soil surface, forming a thick, self-repairing mat.
Microclover is a cultivar of white clover that has smaller leaves and a lower growth profile, typically topping out at four to six inches. This variety is favored for mixed turfgrass lawns because it handles foot traffic better and maintains a denser, more uniform appearance than traditional white clover. Its compact growth ensures maximum light exclusion at the soil level.
In contrast, Crimson Clover (Trifolium incarnatum) is a fast-growing annual used as a temporary cover crop or green manure. It establishes quickly and grows upright, often reaching heights of 18 to 36 inches. While it provides rapid, seasonal weed suppression, it must be replanted each year and is not suitable for permanent groundcover.
Establishing and Maintaining Clover Coverage
Effective weed prevention with clover begins with thorough site preparation before seeding. It is essential to remove or kill any existing perennial weeds, as clover struggles to outcompete established, deep-rooted plants. A firm, clean seedbed is necessary to ensure excellent soil-to-seed contact for successful germination.
Clover should be sown at a higher density than when used as a forage crop to create a dense weed barrier. A recommended broadcast seeding rate for a pure clover stand is approximately 6 to 15 pounds per acre, with the higher end promoting faster and denser coverage. Planting is best done in the early spring or late summer/early fall when soil moisture is adequate and temperatures are moderate.
Consistent watering is needed immediately following seeding to encourage germination, as clover seedlings are vulnerable to drying out. Once established, maintenance practices help keep the cover dense and suppress weeds. Mowing the clover to a height of three to four inches encourages the plant to spread laterally rather than focusing energy on tall flowering stems, reinforcing the dense, weed-excluding mat.
Situations Where Clover May Not Be Ideal
While clover is highly effective for general weed suppression, it presents challenges in certain horticultural contexts. The plant’s aggressive spreading habit can make it a strong competitor with low-growing vegetables or flowers, potentially reducing their yield. Its dense growth makes it difficult to manage in garden beds and can creep over edging into adjacent areas.
Clover is also less effective against weeds that possess deep taproots, such as dandelions or thistles. These established perennial weeds often require pre-seeding removal or manual extraction because their roots access water and nutrients far below the clover’s rooting depth. The plant’s low tolerance for heavy foot traffic is another limitation, as repetitive use can break the stems and thin the coverage, creating open patches where weeds can germinate.