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Spiny emex (Rumex hypogaeus)

Spiny emex is a widespread weed of Australian crops, pastures and other disturbed areas, where dense growth can compete with and smother useful plants. Its hard, sharp fruits can injure livestock, wildlife and people, and can contaminate produce.

Key facts

Type: Weed, herb.

Native to: Southern Africa.

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

Other names: Doublegee, Three-corner Jack, Goat’s Head Burr, Cape Spinach.

Best time to act: Look for seedlings mainly in winter and spring, and treat them shortly after emergence; germination can occur at other times when soil moisture is adequate.

Identification

  • A low-growing, somewhat fleshy annual herb with stems up to 60 cm long and plants up to 40 cm high.
  • Its triangular to egg-shaped leaves are 2–9 cm long and 1–6 cm wide, with undulating margins.
  • Female flowers form small, unstalked clusters that develop into hard, brown fruits with three sharp, spreading spines.
  • The ripe fruit is about 1–1.1 cm long, with spines up to 0.5 cm long; the seed is enclosed inside the woody fruit.
  • Look-alike: Lesser Jack (Rumex spinosa) can occur alongside it but is more erect and has smaller fruits, 0.4–0.7 cm long, with shorter spines of 1–2 mm; Spiny emex grows close to the ground and has larger fruits.

Where it grows

It occurs across all mainland states, is largely absent from tropical areas, and has also been recorded in the ACT and Tasmania, mainly in open or disturbed sites such as cropping and grazing land, roadsides, creek edges and floodplains.

Why it matters

  • It competes with crops and pasture and can smother desirable plants; more than 900 plants per square metre have been recorded in Western Australia.
  • South Australian studies found that about 11 plants per square metre reduced wheat yields by almost 40%, and spiny fruits can contaminate dried grapes.
  • Leaves contain oxalates that can be toxic to sheep and cattle if large amounts are eaten; sharp fruits can injure animals, cause lameness and lead to infected foot wounds.
  • Fruits can injure bare feet, penetrate light footwear and puncture small tyres such as bicycle tyres.

How it spreads

  • Fruits spread when their spines attach to shoes, tyres, animals or containers of produce.
  • They can contaminate fodder, particularly lucerne hay, poorly graded clover seed and imported feed wheat.
  • Fruits float and can spread along watercourses and with floods.

Control options

  • Grub out or manually remove small infestations and isolated plants; completely destroy seeding plants by burning.
  • Fence off small infested areas to limit spread by stock, people and vehicles.
  • For large infestations, shallow cultivate in late summer to encourage autumn germination, then kill seedlings by cultivation or registered herbicides; avoid deep ploughing because it can bury seed and induce dormancy.
  • Aim to kill plants shortly after emergence and continue control for several years because seeds can remain dormant for more than four years.

Hygiene and washdown

  • Check and remove spiny fruits from boots, tyres, machinery and containers before moving them from infested areas.
  • Avoid moving contaminated fodder, seed or produce, and take care around watercourses where floating fruits may spread.
  • 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: Regionally prohibited / regionally controlled / restricted weed (varies by region). Where it is regionally prohibited, landowners must take all reasonable steps to eradicate it on their land. Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • 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: Declared weed, Class B. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • 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
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • 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