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Buffalo burr (Solanum rostratum)

Buffalo burr is a minor weed of Australian crops and pastures, and also occurs on roadsides. Its sharp prickles can injure people and stock, and its toxic plant parts have been recorded as causing stock poisoning.

Key facts

Type: Weed, herb.

Native to: Mexico and the southern United States.

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

Other names: Pincushion Nightshade, Watermelon-leaved Nightshade.

Best time to act: Seeds germinate in autumn, plants grow rapidly in winter and flower in late spring and summer, so look for plants and treat them before they develop seeds.

Identification

  • This is a sprawling annual herb, commonly about 0.2–0.4 m high and across, with plants sometimes reaching 1 m.
  • Its stems have greyish-green, star-shaped hairs, sticky hairs and sharp, straw-coloured prickles up to 10 mm long.
  • The alternate, deeply lobed leaves are hairy and have many straight, needle-like prickles on both surfaces.
  • Yellow flowers grow in stalked clusters between the leaves, and their green calyxes are densely covered in prickles.
  • The dry, globular fruits are enclosed in a prickly casing and contain 50–120 dark brown to black seeds.
  • Look-alike: Solanum sisymbriifolium has similar leaves, but is a shrub over 1 m tall with white flowers and bright red fruits bearing only a few small prickles at the base.

Where it grows

In Australia it occurs in sub-humid temperate to warm-temperate regions, especially the southern mainland wheatbelt, in disturbed paddocks, fallow areas and along roadsides.

Why it matters

  • It is principally a weed of pastures and crops, although its impact is described as minor because of widely adopted herbicide use.
  • The prickly fruits can cause physical injury to people and stock, especially around the nose and mouth.
  • All parts are toxic, and stock poisoning has been recorded, though records are few.
  • It has also been recorded as a contaminant of cereal seed.

How it spreads

  • Burr fruits can spread when they attach to animal fur, sheep's wool, clothing or other fabrics.
  • Old plants can blow along the ground as their fruits disintegrate, releasing seeds.

Control options

  • Manually remove plants where practical, especially before they produce seed.
  • Ploughing or tilling can remove larger infestations.
  • Use registered herbicides according to their labels; some herbicides control seedlings but not older plants, while others work on more mature plants.

Hygiene and washdown

  • Check clothing and other fabrics for prickly fruits and remove them before leaving infested areas, as the fruits can attach and carry seeds.
  • 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: 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: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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

Sources