Clover is often preserved because it fixes nitrogen from the atmosphere into the soil, naturally fertilizing surrounding plants. Clover also exhibits better drought tolerance than many turfgrasses, making it a desirable component in lawns or food plots. Achieving this selective weed control requires specialized herbicides that distinguish between grasses and broadleaf plants like clover. This targeted approach is possible because grasses and clover have fundamentally different internal structures that herbicides can exploit to eliminate one without harming the other.
Understanding Selective Grass Herbicides
Selective control of grass weeds relies on the physiological difference between monocots (all grasses) and dicots (clover and other broadleaf plants). The chemicals used are known as grass-selective herbicides, often called graminicides. These compounds target a specific enzyme found in the grass family, Poaceae, which is crucial for their survival.
The primary active ingredients are Fluazifop-P-butyl, Clethodim, and Sethoxydim. These chemicals inhibit the enzyme acetyl-CoA carboxylase (ACCase), necessary for the synthesis of lipids within the plant. Grasses rely on this particular form of the ACCase enzyme for cell membrane formation and growth. Broadleaf plants like clover possess a different form of the ACCase enzyme that is not affected by these herbicides, allowing them to remain unharmed.
Once absorbed through the foliage, the herbicide moves systemically throughout the plant, accumulating in the growing points. Inhibiting lipid production causes the grass to stop growing almost immediately. Discoloration, such as yellowing or reddening, appears on the newer growth within a few days. Complete necrosis usually occurs within two to three weeks, depending on the weed species and environmental conditions.
Practical Application and Safety Guidelines
Application Guidelines
Effective use depends on applying the herbicide when target grass weeds are actively growing and not under stress. Grasses stressed due to drought, high temperatures, or poor fertility will not effectively translocate the herbicide, leading to poor control. Applications are most effective when annual grasses are young, typically at the three to five-leaf stage before they begin tillering.
Proper mixing requires the addition of a spray adjuvant, such as a crop oil concentrate, to help the chemical penetrate the waxy surface of the grass leaves. The herbicide should be applied with a sprayer calibrated to deliver a consistent volume, ensuring complete coverage of the target weeds. Avoid applying the herbicide if heavy rainfall is expected within one hour, though many formulations are rainfast shortly after drying.
Safety Precautions
Safety precautions are mandatory when handling and applying these chemicals. Users must wear appropriate personal protective equipment (PPE), including chemical-resistant gloves, long sleeves, long pants, and eye protection. After application, a restricted entry interval (REI) specified on the product label must be observed before people or pets can safely re-enter the treated area. Spraying should also be avoided during windy conditions to prevent drift onto non-target plants.
Cultural Practices and Non-Chemical Methods
While selective herbicides offer the quickest way to remove grass weeds, cultural practices can help reduce the need for chemicals and favor the growth of clover. Mowing at a higher setting is a simple strategy, as taller clover plants can shade the soil surface, inhibiting the germination and growth of new grass seeds. Manual removal is an option for small, isolated patches of grass, provided the entire root system is extracted to prevent regrowth.
Optimizing soil health helps the desired clover outcompete the unwanted grasses. Clover thrives in well-drained soil with balanced nutrients. Ensuring proper soil pH and fertility will encourage dense clover stands that naturally suppress weeds. Grasses struggle to establish themselves under these conditions. These preventative measures, combined with targeted chemical application, offer a comprehensive approach to managing a clover stand free of grass weeds.