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Madras thorn (Pithecellobium dulce)

Madras thorn is cultivated in north Queensland from Townsville to Cairns and around Darwin, and is not yet naturalised in Australia. It is a serious weed elsewhere, with potential to form dense thickets and invade tropical open forests and pastures; it is declared a Class 1 pest plant throughout Queensland.

Key facts

Type: Weed, tree.

Native to: North, Central and South America, from California through Mexico to Venezuela.

Established in: QLD, NT.

Other names: Manila tamarind, monkey pod.

Best time to act: Search for plants throughout the year and treat them before pods mature, then revisit the site to check for regrowth and seedlings.

Identification

  • It is a shrub or small, multistemmed tree that can grow to 20 metres tall.
  • Straight, short, stout thorns may occur in pairs at the base of the leaves.
  • Each leaf has one pair of pinnae, each bearing one pair of ovate to obovate leaflets; the leaflets are often variegated.
  • White or cream, fragrant flowers form globular heads about 1 centimetre wide.
  • The coiled, often twisted pods are green or slightly pinkish and contain shiny black seeds about 1 centimetre long, surrounded by edible white pulp.
  • Look-alike: Bauhinia leaves may look similar at a glance, but they are two-lobed rather than bipinnate.
  • Look-alike: Ice-cream bean (Inga edulis) has pinnate leaves with a winged rachis and pods that are not coiled.

Where it grows

In Australia it is cultivated in north Queensland from Townsville to Cairns and around Darwin, and can grow in dry areas, brackish water and poor soils.

Why it matters

  • It can grow in poor soils and dry or brackish conditions, forming dense thickets.
  • It is potentially invasive in tropical open forests and pastures.
  • It is a serious weed in places outside Australia.

How it spreads

  • It reproduces by seed, which is dispersed by birds, and can readily grow from seed.
  • It can also reproduce from cuttings and root suckers; root damage can trigger suckering.

Control options

  • Wear protective gear when working around plants, and hand-pull small seedlings where practical, removing the roots.
  • For larger plants, use an approved physical or herbicide method, such as cut-stump treatment with a herbicide registered for that use; follow the product label and local advice.
  • Avoid damaging roots during removal, and revisit treated sites to find and control regrowth and new seedlings.
  • Check current local requirements and report suspected infestations to the relevant state or territory biosecurity agency, including Biosecurity Queensland in Queensland.

Hygiene and washdown

  • Clean seeds, plant material and soil from boots, tools and machinery before leaving an infested area, and avoid moving contaminated soil or plant waste to clean 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: Restricted matter, categories 2, 3, 4, 5. Report it to Biosecurity Queensland within 24 hours; do not give it away, sell or release it into the environment; do not move it; do not keep it. 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: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • 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)
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources