The appearance of clover and crabgrass in a lawn is a common frustration for homeowners striving for uniform turf. These two pervasive weeds require distinctly different control strategies due to their fundamental botanical differences. Clover is a broadleaf perennial, while crabgrass is a grassy annual, meaning they respond to different chemical and physical controls. Successfully eliminating these weeds and preventing their return involves a dual-strategy approach that addresses their unique biology and integrates long-term cultural practices.
Manual and Natural Removal Methods
For small infestations or non-chemical solutions, physical removal offers an immediate, targeted approach. Clover patches are best addressed by hand-pulling, especially when the soil is moist, which allows the shallow roots to be removed completely. Clover thrives in nitrogen-poor soil; applying a high-nitrogen fertilizer naturally discourages its growth, allowing turfgrass to outcompete the clover. A household vinegar solution with a high acetic acid concentration can be applied as a natural spot treatment for clover, though caution is required. This mixture is non-selective, meaning it will burn and damage any surrounding grass blades it touches. Crabgrass is most effectively removed by hand when the plants are young, before they mature and set seed. Since crabgrass has a fibrous, shallow root system, it can often be teased out of the soil easily using a weeding tool. Dispose of the entire plant to prevent seed heads from spreading.
Targeted Chemical Control for Clover
Controlling clover requires the use of selective broadleaf herbicides designed to target dicot plants without harming turfgrass. These products typically contain a combination of active ingredients, such as 2,4-D, MCPP (mecoprop), and Dicamba, which disrupt the weed’s growth hormones. Using a blend of these chemicals often provides more comprehensive control than a single ingredient. The most effective application timing for these post-emergent herbicides is when the clover is actively growing, allowing the plant to absorb the chemicals through its foliage. Fall applications are often superior because the clover is transporting carbohydrates to its root system for winter storage, pulling the herbicide deeper into the roots for a more thorough kill. Liquid applications generally offer better coverage and adherence to the waxy clover leaves compared to granular products. When spraying, avoid drift onto desirable ornamental plants, as these herbicides will damage or kill any broadleaf species they contact.
Targeted Chemical Control for Crabgrass
Pre-Emergent Control
Crabgrass control is primarily a matter of timing due to its annual life cycle, and the most successful strategy involves a pre-emergent herbicide application. Crabgrass germinates from seed when the soil temperature consistently reaches 55 to 60 degrees Fahrenheit at a depth of one inch. Applying a pre-emergent herbicide before this germination window creates a chemical barrier in the soil that kills the seedling as it attempts to sprout. Common active ingredients include Prodiamine and Pendimethalin, which prevent cell division in the emerging root system. These products require moisture from rain or irrigation to activate and form the protective barrier.
Post-Emergent Control
If the timing is missed and crabgrass has already sprouted, a post-emergent herbicide becomes necessary. The most common and effective chemical is Quinclorac, which is selective and will not harm most common lawn grasses. Post-emergent control is most successful when the crabgrass is young, ideally in the two- to five-leaf stage, before it has developed multiple tillers. Larger, more mature plants require higher concentrations or multiple applications, making post-emergent treatment less efficient than prevention. Eliminating plants before they reach the reproductive stage is paramount, as a single mature plant can produce tens of thousands of seeds.
Long-Term Prevention Through Proper Turf Care
The most sustainable way to prevent the return of both clover and crabgrass is to cultivate a dense, healthy turf that naturally crowds out weed growth. Adjusting the mowing height is a simple yet highly effective cultural control practice. Raising the mower deck to a height of three to four inches allows the grass blades to shade the soil surface. This shading is particularly damaging to crabgrass, which requires sunlight to germinate, and it also cools the soil, further inhibiting germination. Proper watering practices also favor the grass over the weeds, as deep, infrequent watering encourages the turf to develop a strong, deep root system. Regular fertilization, especially with nitrogen, is directly linked to reducing clover populations. Clover is a legume that can fix its own nitrogen from the air, giving it an advantage in nutrient-poor lawns, so providing a consistent source of nitrogen to the turf eliminates this advantage. A thick, well-fed lawn forms a physical barrier against all weed seeds, making it difficult for them to establish themselves. Maintaining sharp mower blades and following the one-third rule also reduces stress on the grass, keeping it dense and vigorous.