Crabgrass (a warm-season annual grassy weed) and clover (a perennial broadleaf weed) are common invaders of home lawns. These two distinct types of weeds require separate management strategies because they differ in biology, growth habits, and susceptibility to treatments. Successfully removing both involves a combination of physical removal, targeted chemical applications, and long-term turf management. This guide details the necessary steps to effectively eliminate these weeds and maintain a healthy, dense lawn.
Physical and Cultural Eradication Methods
When weeds are young or present in small numbers, non-chemical removal techniques offer an immediate solution. For crabgrass, the most effective physical method is hand-pulling the plant before it produces seeds. Remove the entire plant, as even small remnants can regrow. Avoid tilling the soil, which can bring dormant seeds to the surface and encourage future germination.
For isolated crabgrass plants, spot treatment with common household products can be effective, such as pouring boiling water directly onto the weed. Alternatively, high-strength horticultural vinegar can be applied. Users must exercise caution because both methods will also kill any surrounding turf grass they touch. These methods are best reserved for weeds growing in sidewalk cracks or small, highly localized patches.
Clover, with its distinct three-lobed leaves and shallow root system, is also easily removed by hand-pulling, especially after rainfall when the soil is moist. Small patches of clover can be smothered by covering them with an opaque material like black plastic or a thick layer of mulch for several weeks. This technique deprives the weeds of the sunlight necessary for photosynthesis, causing them to die back.
Adjusting cultural practices can drastically reduce a lawn’s susceptibility to both types of weeds. Mowing the turf at a higher setting (ideally between three and four inches) helps the grass blades shade the soil surface. This shading blocks the light crabgrass seeds need to germinate and makes it difficult for clover to establish. Practicing deep, infrequent watering encourages the lawn’s roots to grow downward, making the turf more robust and competitive against the shallow root systems of both weeds.
Targeted Chemical Solutions for Existing Weeds
When physical removal is impractical due to the size or density of the infestation, chemical solutions are necessary. Because crabgrass is a monocot (grassy weed), it requires a selective post-emergent herbicide designed to target grasses without harming the surrounding turf. Products containing the active ingredient quinclorac are effective against crabgrass, particularly when the weeds are young.
Optimal timing for post-emergent treatment is when crabgrass plants are still in their early growth stage, typically having only two to four leaves. Larger, more mature plants that have developed tillers or seed heads are harder to kill and often require a second application several weeks after the initial treatment. This second application ensures that any partially injured plants or those missed in the first round are eliminated.
Clover is classified as a dicot, or broadleaf weed, and is susceptible to a different class of selective herbicides than crabgrass. Effective post-emergent products for clover commonly contain active ingredients such as 2,4-D, MCPP (mecoprop), or dicamba. These chemicals interfere with the plant’s growth hormones, causing the clover to twist and die back over days or weeks.
Clover is easier to control chemically than mature crabgrass, but treatment is most successful when the weed is actively growing during mild temperatures. Regardless of the target weed, it is imperative to read and precisely follow the instructions provided on the herbicide label. Adhering to the label ensures the correct mixing ratio, minimizes the risk of damaging the lawn, and guarantees user safety.
The Prevention Strategy: Long-Term Turf Health
The most successful long-term strategy involves preventing seeds from germinating and promoting overall turf health. For crabgrass, prevention relies on the timely application of a pre-emergent herbicide, which forms a chemical barrier in the soil. This barrier stops the crabgrass seed from successfully sprouting after germination.
This pre-emergent application must occur before the soil temperature consistently reaches 55 to 60 degrees Fahrenheit, which is when crabgrass seeds begin to awaken. Applying the product too late means the seeds will have already germinated, and the treatment will be ineffective against established plants. Pre-emergent herbicides are a preventative measure and do not kill existing, visible weeds.
Clover often flourishes in lawns deficient in nitrogen because it is a legume capable of fixing its own nitrogen from the atmosphere. To discourage clover, soil testing is recommended to identify specific nutrient imbalances, particularly low nitrogen levels. Implementing a consistent fertilization schedule that provides adequate nitrogen favors the growth of turf grasses.
Creating a dense, healthy turf canopy acts as a physical barrier against both crabgrass and clover. Practices such as aeration (which relieves soil compaction and improves water penetration) and overseeding (which introduces new grass plants) thicken the lawn. A thick lawn physically blocks the sunlight necessary for weed seeds to germinate, making it difficult for both weeds to gain a foothold.