Nutsedge, commonly known as nutgrass, is a perennial weed that quickly takes over turf and garden areas. This aggressive plant includes species like yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). Standard herbicides designed for broadleaf or grassy weeds are ineffective because nutsedge is biologically a sedge, requiring a specialized chemical approach. Eradication requires the use of systemic, post-emergent herbicides specifically formulated to target its unique reproductive structure for long-term management.
Identifying the Target: Understanding Nutsedge Biology
Nutsedge is difficult to eradicate because of its distinctive growth habit and subterranean storage organs. Its stem is triangular in cross-section, which differentiates it from true grasses that have round or flattened stems. This sedge grows rapidly, often appearing taller than the surrounding turf just days after mowing, making it highly visible.
The plant’s resilience is tied to its underground structure, which consists of rhizomes and small, starchy tubers called nutlets. These tubers allow the plant to regrow even if the above-ground foliage is destroyed. A single nutsedge plant can produce thousands of new nutlets in a single season, and these nutlets can remain dormant and viable in the soil for several years. This ability to regenerate from the tubers means that any successful chemical treatment must be systemic, traveling from the treated leaves down to the underground nutlets to prevent regrowth.
The Chemical Arsenal: Effective Herbicides
Eradicating nutsedge requires selective post-emergent herbicides absorbed by the foliage and translocated throughout the entire plant system, including the nutlets. The most effective active ingredients (AIs) interfere with the plant’s growth processes, particularly those that target the underground tubers. These specialized AIs are selective, controlling nutsedge without causing damage to most established turfgrasses.
The most widely recommended AI for nutsedge control is Halosulfuron-methyl, often sold under trade names like SedgeHammer. This sulfonylurea herbicide is effective against both yellow and purple nutsedge and is safe for use on warm-season and cool-season turfgrasses. Halosulfuron-methyl is absorbed by both the roots and foliage, but visible symptoms like yellowing and wilting can take up to two weeks to appear.
Another effective AI is Sulfentrazone, frequently found in combination products. Sulfentrazone provides faster control than halosulfuron, with injury symptoms appearing within a few days of application. It works on established nutsedge and as a pre-emergent on seeds, though it does not provide long-term control of established nutlets on its own. Imazosulfuron is a third systemic herbicide option that inhibits the growth of susceptible weeds. Pre-emergent control is possible with AIs like S-metolachlor, which targets newly germinating nutsedge seedlings, but this product does not control plants emerging from established nutlets.
Strategic Application and Timing
The success of a chemical application relies on proper timing and technique to ensure the herbicide reaches the underground tubers. Post-emergent nutsedge herbicides are most effective when applied early in the season, typically in the late spring or early summer, when the plants are young and actively growing. This timing maximizes the translocation of the systemic herbicide to the nutlets, as the plant is efficiently moving nutrients from its leaves to its roots.
Application is ideally made when the nutsedge plants have only three to five leaves, before they invest significant energy into producing new tubers. Applying the herbicide after the plants start forming new nutlets later in the summer significantly reduces the overall control achieved. To maximize the herbicide’s ability to penetrate the nutsedge’s waxy foliage, add a non-ionic surfactant or an adjuvant to the spray solution. This additive helps the chemical spread and stick to the leaves, improving absorption.
A single treatment is rarely sufficient for full eradication due to dormant nutlets in the soil. A sequential application is necessary, typically recommended four to six weeks after the initial treatment, to kill any new sprouts. Always read the product label carefully, as it specifies the correct mixing ratios, acceptable turfgrass species, and necessary personal protective equipment (PPE) for safe handling. Avoid mowing for a couple of days before and after application to allow for maximum herbicide uptake.
Long-Term Management and Prevention
While herbicides are necessary for immediate control, long-term management depends on modifying the environment to make it less hospitable for the weed. Nutsedge thrives in wet, poorly drained, and compacted soils, often indicating an underlying moisture issue. Adjusting irrigation practices is a primary non-chemical control measure; switch from frequent, shallow watering to deeper, less frequent watering to dry out the upper soil layer where nutsedge germinates.
Improving soil drainage through aeration or correcting low spots where water collects will further discourage nutsedge establishment. Maintaining a thick, healthy turfgrass stand is one of the best forms of natural prevention, as dense grass shades the soil, inhibiting nutsedge germination and initial growth. Mowing at the highest recommended height for the specific turfgrass species is a simple cultural practice that helps shade the soil surface. Hand-pulling is not recommended, as it often leaves the nutlets behind and can stimulate the remaining tubers to sprout, potentially worsening the infestation.