Clover, particularly white clover (Trifolium repens), is often viewed as an unwelcome intruder in manicured lawns. Its proliferation signals that the underlying conditions of the lawn favor clover’s growth over that of turfgrass. This shift in the ecological balance is the root cause of clover dominance. Understanding the environmental factors that encourage this growth, along with clover’s unique benefits, offers a clear path toward managing its coverage effectively.
The Environmental Conditions Encouraging Clover Growth
Clover thrives when turfgrass struggles, primarily due to a nitrogen deficit in the soil. Clover is a legume, meaning it forms a symbiotic relationship with Rhizobium bacteria in its root nodules, allowing it to “fix” atmospheric nitrogen gas into a usable organic form. This natural ability gives clover a competitive advantage in nitrogen-starved soil, where grass must rely on external fertilizer applications to survive.
Mowing the grass too short, often below three inches, causes stress to the turfgrass plant, weakening its root system and thinning the canopy. Clover naturally grows low to the ground and spreads horizontally via runners called stolons, making it largely unaffected by a low cut. This habit allows clover to quickly spread and dominate the sunlight and space at the soil level where the weakened grass cannot compete.
Clover is more tolerant of unfavorable soil conditions, such as high compaction. Grass roots struggle to penetrate dense, compacted soil, which restricts the movement of air, water, and nutrients. Clover’s long taproot allows it to draw moisture and nutrients from deeper in the soil than shallow-rooted turfgrass, permitting it to flourish where the grass may be thinning out.
Changes in herbicide use have also played a role in clover’s resurgence in lawns. In the mid-20th century, clover was purposefully included in grass seed mixes, but the introduction of broadleaf weed killers effectively labeled clover as a weed. However, many homeowners now either avoid using these selective herbicides or use formulations that do not effectively target clover, allowing the plant to spread without chemical intervention.
Clover’s Unexpected Benefits
Clover possesses several attributes that were historically valued in lawns. Its most recognized benefit is its nitrogen-fixing capability, which acts as a natural fertilizer for the surrounding soil and turfgrass. When clover leaves or roots decompose, the fixed nitrogen becomes available to neighboring grass plants, reducing or sometimes eliminating the need for synthetic nitrogen fertilizers.
The plant also demonstrates resilience to environmental stressors, especially during dry and hot weather. Clover stays green longer than most turfgrass species due to its deep root system, which allows it to access deeper soil moisture. This drought tolerance means a clover-mixed lawn often maintains a desirable green color without the frequent watering required by a pure turfgrass lawn.
Clover is also highly beneficial to local ecosystems, particularly for pollinating insects. Its small, spherical white flowers provide a source of easily accessible nectar for honeybees, bumblebees, and other beneficial pollinators. Embracing a mixed grass and clover lawn supports local biodiversity and helps sustain these insect populations.
Effective Strategies for Reducing Clover Coverage
The most effective strategy for reducing clover involves changing the environment to favor dense turfgrass growth. This begins with adjusting fertilization practices, as clover cannot thrive in soil with high nitrogen levels. Applying a nitrogen-rich fertilizer will significantly boost the competitiveness of the grass, causing it to grow thick and tall enough to shade out the low-growing clover.
Cultural practices, such as raising the height of your mower blade, are also highly effective. Setting the mower to cut between 3 and 4 inches allows the grass blades to grow taller and create a dense canopy that blocks sunlight from reaching the clover leaves below. Shading the clover hinders its growth and prevents it from spreading effectively across the lawn surface.
Watering the lawn deeply but infrequently encourages the grass to develop deeper, more robust root systems. Aiming for about one inch of water per week, delivered in one or two sessions, promotes a resilient lawn that is better able to compete with clover for resources. Shallow, daily watering encourages shallow grass roots, which makes the turf more susceptible to drought and competition from weeds.
For small, isolated patches, manual removal is a viable option. Because clover spreads through stolons that root at nodes, it is important to pull out the entire plant, including the runners, to prevent regrowth. For larger areas or persistent infestations, selective broadleaf herbicides can be used.
Selective herbicides target broadleaf plants like clover while leaving turfgrass unharmed. Products containing active ingredients such as dicamba, MCPP (mecoprop), or triclopyr are known for their effectiveness against white clover. Fall is often the most effective time for application, as the clover is actively drawing resources down into its root system in preparation for winter, making it more susceptible to the chemical treatment.