Nutgrass is the common name for the perennial weeds yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). This aggressive, grass-like sedge is considered one of the world’s most difficult weeds to manage. Accurate identification requires examining its unique visual and tactile characteristics.
Identifying Features Above Ground
The most definitive physical trait of nutgrass is its solid, upright stem, which has a distinctly triangular cross-section. This shape is unique from true grasses and can be confirmed by rolling the stalk between your thumb and forefinger.
The leaves of nutgrass are typically waxy and glossy, emerging in sets of three from the base of the plant. Yellow nutsedge exhibits a bright yellow-green color, which often makes it stand out against the darker green of turfgrass. Conversely, purple nutsedge generally has darker green foliage.
Nutgrass displays aggressive, rapid growth, particularly during the warm summer months. This vigorous upward growth causes the plant to shoot up quickly, often towering over surrounding lawn grasses within a few days of mowing. This difference in height is a primary visual cue for spotting the weed.
The Unique Underground System
The persistence of nutgrass is due to its complex network of subterranean structures, which function for energy storage and reproduction. Below the soil line, the plant produces wiry, horizontal stems called rhizomes that spread out to colonize new areas. These rhizomes can extend up to a foot deep and are the plant’s primary means of short-distance spread.
The rhizomes also produce small, hardened, potato-like structures known as tubers or “nutlets,” which give the plant its common name. These nutlets are typically pea-sized (10 to 25 millimeters long) and are initially white before maturing into a firm, dark brown or black state. The tubers are packed with starch, allowing the plant to survive adverse conditions like drought or frost for many years.
A key distinction between the two species is the arrangement of these nutlets. Yellow nutsedge typically forms tubers singly at the tips of its rhizomes. Purple nutsedge produces its tubers in chains, connected by short lengths of rhizome.
Differentiating Nutgrass from Common Grassy Weeds
Telling nutgrass apart from common grassy weeds is simple once the core differences between a sedge and a true grass are known. All true grasses possess stems that are either round or flattened, lacking the pronounced edges of the nutgrass stem. This fundamental structural difference is the most reliable way to make a positive identification.
Texture and color provide clear contrast, as many common grass weeds have softer, flatter leaves. Nutgrass leaves are often V-shaped in cross-section with a noticeable mid-rib, unlike the flatter blades of most turfgrasses. The plant’s reaction to mowing is also a strong visual indicator. Because nutgrass stems and leaves are rigid and upright, the blades often appear ragged, torn, or frayed immediately after mowing. This aggressive growth rate, combined with the frayed appearance and triangular stem, confirms the presence of nutgrass.