Nutgrass
Cyperus rotundus L.
Nutgrass is a persistent perennial sedge that spreads via underground tubers, making it one of the hardest weeds to eradicate in turf and garden beds.
Nutgrass is an erect, grass-like perennial sedge growing from a network of underground rhizomes that terminate in small, hard tubers ("nuts"). Leaves are glossy, dark green, arranged in sets of three from the base, with a distinct midrib and a waxy sheen that distinguishes them from true grasses, which have leaves in two ranks. Stems are triangular in cross-section, a key identifying feature of sedges. Flower heads appear in summer, held on a triangular stalk above the foliage, with reddish-brown to purplish spikelets in an umbrella-like cluster. The tubers, typically 1–2 cm and chestnut brown to black, form in chains along rhizomes at depths from just below the surface to 30 cm or more, and are the primary means of survival and spread.
Nutgrass (also called yellow nutsedge or nut grass) is widespread across Australia, particularly in warmer coastal and subtropical regions of Queensland, New South Wales and northern parts of other states, though it also persists in cooler climates. It thrives in moist, well-irrigated or poorly drained soils and is common in turf, garden beds, nursery containers, irrigation channels and disturbed or cultivated ground.
Growth is most vigorous from spring through to autumn when soil temperatures are warm, with the plant dying back to dormant tubers over winter in cooler regions. A single plant can produce large numbers of tubers within one growing season, and these tubers can remain viable in the soil for several years, sprouting repeatedly even after the visible foliage is removed.
Management is difficult because tubers are not killed by cultivation alone — in fact, tillage often fragments rhizomes and spreads viable tubers further. Effective control relies on an integrated approach: repeated removal of top growth to exhaust tuber reserves, improving drainage where waterlogging favours the weed, physical barriers or solarisation in garden beds, and targeted use of registered herbicides at appropriate growth stages. Follow-up treatments over multiple seasons are usually necessary, as a single control effort rarely eliminates the underground tuber bank.
How to identify
- Foliage: Clumps of glossy, dark green, grass-like leaves with a triangular stem — feel the stem cross-section between your fingers to distinguish it from true grasses (which have round or flattened stems).
- Growth pattern: Emerges in patches that spread outward, often expanding rapidly through turf, garden beds or nursery pots during warmer months.
- Confirming the weed: Dig around the base of a plant to expose the root system — a chain of small, hard, dark brown to black tubers along whitish rhizomes confirms nutgrass. This is the most reliable field check, since foliage alone can be mistaken for other sedges or grasses.
- Flower heads: In summer, look for reddish-brown to purplish umbrella-shaped flower clusters on a triangular stalk rising above the leaves.
- Lookalikes: Purple nutsedge (a closely related species) is very similar but tends to have darker, more purplish flower heads and tubers connected in longer chains; mullumbimby couch and other sedges lack the true tubers and have fibrous, non-tuberous root systems — digging up the root system is the most reliable way to tell them apart.
- Persistence check: If a patch regrows repeatedly after mowing or spraying with no lasting effect, this points strongly to a tuber-based sedge like nutgrass rather than an annual grass or broadleaf weed.
Registered products we stock
No products match those filters.