The presence of unwanted broadleaf plants within a desired clover groundcover presents a common management challenge. Clover, typically Trifolium repens (white clover), is often integrated into lawns or pastures for its resilience and ability to fix nitrogen into the soil, which naturally fertilizes surrounding plants. When competing weeds like dandelions, plantain, or chickweed invade, the goal is selective removal: eliminating competitors while preserving the beneficial clover. Achieving this requires understanding non-chemical maintenance practices and the specific action of different herbicide ingredients.
Cultural Practices for Minimizing Weed Growth
Maintaining a dense, vigorous clover stand is the first line of defense against weed invasion, as strong plants naturally suppress competitors. Clover is highly resilient and generally thrives when mowed at a lower height than is typical for turfgrass. Cutting the area to a height of approximately two to three inches helps the clover canopy shade the soil surface, limiting the light available for weed seed germination and growth. Consistent mowing also prevents most broadleaf weeds from reaching the height needed to produce and scatter seeds, stopping their reproductive cycle.
Proper watering techniques also favor clover over many shallow-rooted weeds. Clover possesses a deep taproot system, which allows it to tolerate drier conditions better than many common weeds. Applying water deeply and infrequently encourages the clover roots to grow downward, making the plants more robust and less reliant on surface moisture. This practice simultaneously discourages the establishment of weeds that require consistent moisture near the soil surface.
The soil health benefits provided by clover are another factor in weed suppression. As a legume, clover hosts symbiotic bacteria that convert atmospheric nitrogen into a usable form in the soil. This natural nitrogen fixation reduces the need for synthetic nitrogen fertilizers, which often stimulate the growth of undesirable grassy weeds. Manually removing any large, isolated broadleaf weeds before they flower or mature is a simple, proactive step that prevents the establishment of new seed sources.
Selective Herbicides That Do Not Harm Clover
When cultural practices alone are insufficient, specific selective herbicides can be employed to target broadleaf weeds without damaging the clover. The most effective active ingredient for this purpose is 2,4-DB (4-(2,4-dichlorophenoxy)butyric acid), often marketed under names like Butyrac. This compound is a type of auxin-mimicking herbicide, but it requires activation by specific enzymes found in susceptible plants, like many common weeds. Clover plants lack the necessary enzyme to rapidly convert 2,4-DB into its toxic form, 2,4-D, which allows the clover to tolerate the chemical while weeds are eliminated.
This inherent selectivity makes 2,4-DB the preferred choice for controlling broadleaf weeds such as curly dock and thistle in established clover stands. Application timing is crucial for maximizing effectiveness and minimizing any temporary clover injury. The herbicide should be applied when weeds are young and actively growing, but generally after the clover has developed its third trifoliate leaf and before it begins to flower.
In addition to 2,4-DB, specialized iron-based herbicides, specifically those containing FeHEDTA (Iron Hydroxyethylenediaminetriacetic acid), offer an alternative selective option. These products cause iron toxicity in broadleaf weeds, leading to rapid discoloration and death, while leaving the clover and surrounding grasses largely unharmed. Iron-based treatments are effective in cooler temperatures, expanding the possible window for application outside the temperature restrictions of some synthetic chemicals. Always follow the manufacturer’s directions precisely regarding concentration and temperature, as incorrect use can still lead to temporary browning or damage to the desirable clover.
Identifying and Avoiding Clover-Killing Chemicals
The greatest risk to a clover groundcover comes from inadvertently applying herbicides designed to eliminate all broadleaf plants, including clover. The single most detrimental ingredient is 2,4-D (2,4-dichlorophenoxyacetic acid), a common component in many standard broadleaf weed killers. This chemical functions as a synthetic auxin, causing uncontrolled and lethal growth in susceptible plants by disrupting cell division and nutrient transport. Since clover is a broadleaf plant, it is highly sensitive to 2,4-D, leading to rapid die-off.
Many popular “weed and feed” products or multi-purpose lawn herbicides contain 2,4-D, often combined with other chemicals like Dicamba and MCPP (Mecoprop) in three-way mixes. Consumers must carefully examine product labels, as these combinations are highly effective at removing broadleaf weeds from turfgrass but will severely damage or eradicate clover. Even low concentrations of 2,4-D can cause significant injury to the clover population, making it imperative to confirm the absence of this chemical when selecting a product intended for clover preservation.
Non-selective herbicides, such as those containing glyphosate, must also be avoided in a clover area unless the intention is to kill all vegetation in a small, isolated spot. Glyphosate works by inhibiting an enzyme pathway common to most plants, meaning it will kill both the weeds and any clover it contacts. The distinction between the clover-safe 2,4-DB and the clover-lethal 2,4-D is the most crucial piece of information for successful selective weed control.