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Lesser jack (Rumex spinosus)

Lesser Jack is an introduced weed of pastures and cultivated land, and its spiny fruits can cause lameness in stock. It can also injure bare feet and puncture light footwear and bicycle tyres.

Key facts

Type: Weed, herb.

Native to: Mediterranean region.

Established in: VIC, SA, WA.

Other names: Doublegee, Erect Emex, Little Jack, Spiny Emex.

Best time to act: Look for seedlings in autumn and control them shortly after emergence; plants flower from late winter to early summer.

Identification

  • It is a low-growing annual herb, up to 60 cm high, with stems up to 80 cm long that may stand upright or lie on or close to the ground.
  • Its hairless, triangular to egg-shaped leaves are 5–12 cm long and 2–8 cm wide, with entire or undulating edges and long leaf stalks.
  • Small, inconspicuous green or whitish male and female flowers occur in clusters in the leaf forks on the same plant.
  • The hard fruits turn brown as they mature and are 4–7 mm long, with three thick spines, each 1–2 mm long.
  • Each fruit contains one glossy, smooth, brown seed or nut.
  • Look-alike: Spiny Emex (Rumex hypogaeus) is the main similar species. Lesser Jack is more erect and has smaller fruits, 4–7 mm long, with shorter spines of 1–2 mm; Spiny Emex grows close to the ground and has fruits 7–11 mm long with spines 2–5 mm long.

Where it grows

In Australia it occurs in disturbed temperate areas such as pastures, road verges and wasteland, and is most common, though still uncommon, in southern Western Australia.

Why it matters

  • Its spiny fruits can cause lameness in stock.
  • Because it grows taller than Spiny Emex, it can be more problematic in cereal crops.
  • The fruits can injure bare feet, penetrate light footwear and puncture bicycle tyres, and the plant has potential to invade disturbed natural areas.

How it spreads

  • Seeds readily attach to clothing, vehicles and animals.
  • Seeds can also spread in contaminated agricultural produce and by water.

Control options

  • Grub out or manually remove small infestations and isolated plants; completely destroy seeding plants by burning them.
  • For large infestations, shallow cultivate in late summer to encourage autumn germination, then kill seedlings by cultivation or registered herbicides.
  • Avoid deep ploughing, which can bury seed and induce dormancy; continue control for several years and aim to kill plants shortly after emergence.
  • Herbicides can be effective but do not eradicate the problem because of the soil seed bank; use registered herbicides and approved methods for the site.

Hygiene and washdown

  • Check and clean clothing, vehicles and equipment to avoid carrying fruits and seeds to new areas.
  • Prevent the movement of contaminated agricultural produce, and take care not to spread seed with water.
  • 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: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • 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: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • 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.

  • 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

Sources