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Purpleflower devil's claw (Proboscidea louisianica)

Purpleflower Devil's Claw is an introduced weed of disturbed sites and agricultural areas in several Australian states. Its clawed fruits can injure livestock, interfere with harvesting and spread seeds by attaching to animals, clothing, machinery and vehicles.

Key facts

Type: Weed, herb.

Native to: Southern North America.

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

Other names: Purple-flowered Devil's Claw, Elephant Tusks, Goat Head, Ram's Horn.

Best time to act: Look for plants during rapid spring and summer growth, with flowering and fruiting mostly from February to March, and treat before flowering.

Identification

  • A low-growing, erect, sticky annual herb, usually 20–50 cm high, with stout, branched stems covered in glandular hairs.
  • Its large, rounded leaves have heart-shaped bases and occur in opposite pairs along the stems.
  • Showy trumpet-shaped flowers are cream, white or purple, with dark orange and purple markings in the throat.
  • The brown or black fruit is 8–30 cm long, with a bulbous capsule and two curved, horn-like claws; it becomes hard and woody as it matures.
  • The capsule contains numerous black or grey, strongly wrinkled seeds about 10 mm long and 6 mm wide.
  • Look-alike: Yellowflower Devil's Claw (Ibicella lutea) has yellow flowers with red or purple markings, usually more densely clustered, and light-brown fruits with short spines at the base.
  • Look-alike: Devil's Claw (Martynia annua) has pink to lavender flowers and smaller fruits, about 3–4 cm long, with claws shorter than the fruit.

Where it grows

In Australia it occurs on disturbed sites such as roadsides, river flats and cultivated areas, in tropical, subtropical, temperate and arid to semi-arid regions.

Why it matters

  • It can compete strongly with summer and horticultural crops, including cotton, and is particularly drought tolerant.
  • Hard, clawed fruits can injure livestock if caught in the mouth or nose, work into the body or feet, or lodge around the mouth and prevent feeding.
  • Woody fruits can interfere with harvesting and damage machinery.
  • It is not known to have a major impact on native flora and fauna, but may displace other herbs, forbs or grasses.

How it spreads

  • The fruit's claws readily attach to passing animals and carry seeds; sheep are considered an especially important means of spread.
  • Seed transport is the only known dispersal mechanism, and a plant can produce up to 8,000 seeds.
  • Cockatoos eat the seeds, but whether this results in seed dispersal is unknown.

Control options

  • Cultivate or hoe plants before flowering; the species reproduces by seed and does not resprout from its roots.
  • If plants have flowered, destroy them properly by burning.
  • Apply registered herbicides to actively growing seedlings or adult plants before flowering, following product directions.

Hygiene and washdown

  • Clawed fruits can attach to clothing, machinery and vehicles; check these for attached fruits and remove them before leaving an infested site.
  • 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: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • 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
  • 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