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Downy thornapple (Datura innoxia)

Downy Thornapple is toxic to stock and people, and can compete strongly with summer-growing and irrigated crops. It is widespread in parts of Australia and can spread through water, contaminated seed, mud and moved plant material.

Key facts

Type: Weed, herb.

Native to: Texas, Mexico and Central America.

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

Other names: Recurved Thorn-apple, Datura inoxia, Datura meteloides.

Best time to act: It flowers and fruits through summer and autumn, and small plants are more susceptible to herbicide than mature plants.

Identification

  • It is a much-branched, bushy annual or short-lived perennial herb that grows to about 1 m high.
  • Its dull greyish-green stems and leaves are covered in erect glandular hairs that feel clammy to the touch.
  • The alternate, stalked leaves are mostly 90–160 mm long and 65–90 mm wide, sometimes larger, and may have a few short, broad lobes near the base.
  • Large, white, trumpet-shaped flowers are borne singly in the branch forks and are 120–190 mm long.
  • The prickly capsules hang or bend downwards; mature fruits are 35–50 mm long and contain many mid- to greyish-brown seeds.
  • Look-alike: Hairy Thornapple (Datura wrightii) is similar, but usually has mostly backwards-facing, non-glandular hairs and flowers often tinged greyish lavender or pink; Downy Thornapple has erect glandular hairs and pure white flowers.
  • Look-alike: Common Thornapple and Fierce Thornapple lack Downy Thornapple’s dense sticky hairs and have erect rather than nodding capsules.

Where it grows

In Australia it occurs across NSW, NT, QLD, SA, VIC and WA, mainly on disturbed ground such as watercourses, flooded areas, irrigated crops, roadsides, neglected sites and around stock yards.

Why it matters

  • All parts of the plant are toxic, with the seeds the most poisonous part.
  • Stock may be poisoned by eating contaminated hay, chaff or silage, although they generally avoid the plant because of its bitter taste and prickly pods.
  • It competes strongly with some crops, especially summer-growing and irrigated crops.

How it spreads

  • Seeds can be carried in water run-off and along watercourses.
  • It may spread as a contaminant of crop seed or in mud attached to vehicles, and can be moved by people growing it as an ornamental.
  • Root fragments moved by machinery have also been recorded as a means of spread.

Control options

  • Mechanical removal is feasible for small infestations.
  • Large stands on cropping land can be removed by ploughing or tilling the soil.
  • Small plants are susceptible to herbicide, but chemical control may be ineffective on mature plants; use registered herbicides according to approved directions.
  • Consult the Australian Pesticides and Veterinary Medicines Authority for current chemical information.

Hygiene and washdown

  • Check vehicles and machinery for mud and plant or root fragments, as these can move the weed to new sites.
  • Avoid moving crop seed contaminated with Downy Thornapple 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: 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
  • 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