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Common thornapple (Datura stramonium)

Common thornapple is an important agricultural weed, and the whole plant is poisonous to stock and people, with the seeds the most toxic part. It competes with crops and may invade native ecosystems, especially along watercourses.

Key facts

Type: Weed, herb.

Native to: Southern USA and Mexico.

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

Other names: Jimson weed.

Best time to act: Look for flowering and fruiting plants through summer and autumn, and treat small plants before they mature.

Identification

  • It is a robust, bushy annual herb that grows to 1.2 m high, though it may flower when only 0.2 m high.
  • Its stems are green and may be purple-tinged or entirely purple; its bright green leaves are alternately arranged and have angular teeth and lobes.
  • The white or lilac flowers are trumpet-shaped and grow singly in the branch forks.
  • Its prickly, egg-shaped fruits are held erect and have about 100–200 slender spines.
  • The capsules open into four segments and shed many pitted, usually black seeds.
  • Look-alike: Fierce thornapple (Datura ferox) also has erect capsules that split into four valves, but it has shorter flowers and fewer, much larger prickles, about 40–60 per capsule, as well as larger seeds.
  • Look-alike: Other Datura species in Australia have capsules that nod or hang down when ripe and open unevenly.

Where it grows

It occurs in all Australian states and the ACT but not the NT, in disturbed places such as cultivated paddocks, wasteland, roadsides, rail reserves and watercourses.

Why it matters

  • The plant is poisonous to stock, and its seeds are the most poisonous part.
  • Stock are usually affected after eating contaminated hay, chaff or silage rather than grazing the bitter plants.
  • Children have also been poisoned after eating the seeds.
  • It competes strongly with crops and may invade native ecosystems, especially along watercourses.

How it spreads

  • Seeds are often transported as contaminants in crop seed, sometimes travelling thousands of kilometres by road or rail.
  • Seeds float and can be dispersed by water.
  • Seeds can also spread in mud attached to vehicles or machinery.

Control options

  • For small infestations, mechanically remove the plants.
  • For large stands on cropping land, plough or till the soil.
  • Follow up in later seasons to remove seedlings germinating from seed stored in the soil.
  • Small plants are susceptible to herbicides, but treatment may be ineffective on mature plants; check registered herbicides and relevant chemical information.

Hygiene and washdown

  • Use crop seed that is not contaminated with thornapple seed.
  • Remove mud from vehicles and machinery before moving between sites.
  • 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 controlled / restricted weed (varies by region). 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: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Declared weed. Weeds Australia lists it as a declared weed in the NT under the Weeds Management Act 2001. Check the NT declared weeds list for its class and what it requires.
  • 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
  • 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

Sources