Nutgrass (Cyperus species) is a highly aggressive perennial weed known for its resistance to standard control methods, making it one of the most frustrating invaders in gardens and lawns. This plant is actually a sedge, often misidentified as a grass, that quickly forms dense patches. Given its stubborn nature, many homeowners search for non-traditional solutions, leading to the question of whether a simple kitchen ingredient, sugar, can kill it. This article explores the science behind this popular home remedy and offers proven alternatives for effective management.
The Biological Challenge of Nutgrass
Nutgrass is notoriously difficult to eradicate because its survival strategy is centered entirely underground. The plant propagates primarily through small, carbohydrate-rich structures called tubers (or nutlets), which form along a vast network of underground stems known as rhizomes. These tubers act as energy storage units, allowing the plant to regenerate rapidly even after the above-ground shoot is cut or damaged.
A single nutgrass plant can produce hundreds or thousands of these nutlets in a single growing season. These tubers can remain dormant and viable in the soil for several years, often surviving at depths of up to 40 centimeters. Simple digging is ineffective because pulling the visible shoot often breaks the connection to the tuber chain, triggering remaining dormant tubers to sprout aggressively and worsening the infestation.
The Sugar Hypothesis: Theory Versus Reality
The theory that sugar can kill nutgrass is rooted in the concept of nitrogen immobilization within the soil. When simple sugar is applied to the soil surface, it provides a massive carbon source for soil microbes. These microbes multiply rapidly and consume the available nitrogen in the soil to fuel their growth, a process called nitrogen immobilization. This effectively starves surrounding plants of this necessary nutrient.
The idea is that nutgrass, a high nitrogen feeder, will be weakened by this sudden deprivation. However, this method is ineffective for long-term control, especially for established infestations. The extensive energy reserves stored in the plant’s underground tubers allow it to withstand temporary nutrient stress that would kill less robust, shallow-rooted weeds.
The nitrogen immobilization effect is temporary, lasting only a few weeks, and requires substantial, impractical quantities of sugar (1 to 5 pounds per 100 square feet) to have any noticeable effect. While sugar can theoretically stress a variety of weeds, it cannot destroy the deep, energy-rich tuber system of nutgrass. Applying sugar is considered a partial, temporary measure that will not achieve complete eradication.
Proven Non-Chemical Control Strategies
Effective nutgrass control requires persistent action focused on exhausting the underground tuber reserves. Manual removal must be done carefully to include the entire tuber chain rather than just snapping off the shoot at the soil line. Trying to pull the visible plant encourages more nutlets to sprout, which is why a small trowel or shovel should be used to dig out the soil 10 to 14 inches deep and wide enough to remove all connected tubers.
Smothering and exclusion techniques are also effective by blocking the sunlight the plant needs to replenish its energy stores. Applying thick layers of mulch or using solid barriers like landscape fabric can suppress growth, forcing the plant to use its tuber reserves.
Another effective non-chemical method is soil solarization, a process best performed during the hottest summer months. This involves covering a moistened, cleared area with clear plastic sheeting for four to six weeks. The plastic traps solar heat, raising the soil temperature to between 110° and 125°F in the top six inches, which is sufficient heat to kill or sterilize the nutlets and rhizomes.
Targeted Herbicide Options
When cultural and manual controls are not practical, a targeted herbicide application is necessary for complete control. Nutgrass is a sedge, meaning it is not controlled by most common lawn herbicides designed for broadleaf or grassy weeds. The most effective solutions are selective, post-emergent herbicides specifically formulated to translocate through the plant and into the underground tubers.
Homeowners should look for products containing active ingredients such as halosulfuron-methyl or sulfentrazone. Halosulfuron-methyl requires about two weeks to show visible signs of injury, while sulfentrazone works faster, with injury appearing within a few days. Because these products are selective, they can control nutgrass without harming desirable turfgrass when applied correctly. Follow all product directions precisely regarding application rate, timing, and temperature restrictions to ensure efficacy and safety.