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Nutgrass (Cyperus rotundus)

Nutgrass is an introduced, naturalised weed recorded across all mainland Australian states and can be locally common in disturbed places. Its persistent underground tubers make it difficult to control, and it can infest crops as well as gardens and other areas around habitation.

Key facts

Type: Weed, herb.

Native to: Africa and Asia.

Established in: QLD, NSW, ACT, VIC, SA, WA, NT.

Other names: Purple nutsedge, Purple nutgrass.

Best time to act: Look for and treat Nutgrass while it is actively growing in the warmer months, with flowering generally occurring in spring and summer.

Identification

  • It is a perennial sedge that grows from slender underground rhizomes bearing woody, oval to ellipsoid tubers about 0.5–1 cm across.
  • Its smooth, three-angled stems are usually 15–30 cm tall, but can reach 60 cm.
  • The leaves are shorter than the stems and 2–6 mm wide.
  • The flower head is usually made up of 3–9 branches, with short, crowded spikes and flattened spikelets; flowering is in spring and summer.
  • Look-alike: Yellow nutsedge (Cyperus esculentus) is a close lookalike; Nutgrass typically has dark tubers borne along its rhizomes, while yellow nutsedge commonly has tubers at rhizome tips.

Where it grows

In Australia it grows in disturbed situations, especially around habitation, and occasionally infests crops.

Why it matters

  • It can be a troublesome weed in disturbed sites and crop areas.
  • Underground rhizomes and tubers make established patches difficult to remove completely.
  • Regrowth from missed tubers can undermine control and allow patches to persist.

How it spreads

  • Rhizomes and tubers can be moved to new sites in soil and on cultivation or earthmoving equipment.
  • Cultivation can break up and redistribute underground parts, helping patches spread.

Control options

  • For small patches, carefully remove the plants and as much of the rhizome and tuber network as possible; contain and dispose of removed material so it cannot regrow or spread.
  • Avoid cultivating or slashing infested ground in ways that break up and move tubers.
  • Where appropriate, use only herbicides registered for Nutgrass and the intended site, and follow the product label and local advice.
  • Check for regrowth and repeat control over successive growing seasons; contact the state or territory biosecurity authority for local advice and any reporting requirements.

Hygiene and washdown

  • Clean soil and plant material from machinery, tools, boots and vehicles before leaving an infested site, and avoid moving contaminated soil to clean areas.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources