Captain Cook tree

Native to the West Indies and tropical South America, Captain Cook tree has often been planted as an ornamental tree in Australia's domestic gardens and public spaces.

Captain Cook tree can invade native vegetation, threaten pasture, and is poisonous to animals and humans. Captain Cook tree has become a highly invasive weed in parts of Queensland.

Captain Cook tree is a restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Cascabela thevetia, previously Thevetia peruviana

Other names

Yellow oleander, cook tree, be-still tree, still tree, lucky nut, foreigner's tree, Mexican oleander

Description

  • Large, attractive tree up to 10m tall.
  • Leaves are narrow, pointed, 5-15cm long, 0.5-1.5cm wide.
  • Flowers are yellow or peach-coloured, waxy, bell-shaped, up to 5cm in diameter.
  • Sap is milky.
  • Fruit is green when young, black when ripe, lantern-shaped, 2.5-4cm in diameter, contains 1-2 seeds.

Habitat

  • Highly invasive in Queensland, especially along creek systems.
  • Found along roadsides and in waste areas, disturbed areas and pastures.

Distribution in Queensland

  • Established infestations found near Mingela and Ingham in north Queensland.

Life cycle

  • Older trees can produce large amounts of seed.
  • Flowers throughout most of year.

Affected animals

  • livestock

Impacts

Environmental

  • Invades native vegetation.

Economic

  • Threatens sustainable pasture production.
  • All parts of plant are poisonous to stock.

Social

  • Highly poisonous if ingested.

How it is spread

  • Spread by dumped garden waste.

Control

Effective control of Captain Cook tree can be achieved by combining mechanical and herbicide treatments or by herbicide treatment alone. Choose control methods to suit your particular situation. All treated areas must be periodically checked and any regrowth treated, or initial treatment efforts will be wasted. Follow-up must be undertaken to ensure a successful control program.

Physical control

  • Small individual plants may be manually removed, taking care to remove roots. This option is not feasible for larger specimens.

Mechanical control

  • Isolated individuals can be grubbed out with a blade, either front- or rear-mounted to a dozer or tractor.
  • Dense infestations can initially be cleared with a cutterbar (if terrain and soil-type permit).
  • Treat remaining broken and exposed stems with basal bark spray as soon as possible following clearing.
  • To ensure a successful control program, regrowth must be sprayed.

Herbicide control

  • Method depends on size of target tree and situation. Use of wetting agent may increase efficacy of herbicides.
  • Herbicides work best when plants are actively growing. Some herbicide treatments may take more than a year to kill Captain Cook trees.
Foliar spray
  • Spray whole plant thoroughly to point of run-off, wetting every leaf during time when plant is actively growing.
  • Foliar spraying is most effective on plants less than 2m high.
  • Don't treat infestations during hot, dry, summer periods; when windy; or when plant is stressed from drought or waterlogging.
  • Add surfactant to herbicide mixture at rates specified on herbicide label.
Basal bark spray
  • For stems up to 5cm in diameter, carefully spray completely around base of plant to 40cm above ground level.
  • For effective control of multi-stemmed plants, each stem must be thoroughly sprayed.
  • Larger trees may be controlled by spraying to greater height — up to 1m above ground level.
Cut stump treatment
  • Cut stems off horizontally as close to ground as possible and immediately (within 15 seconds) swab or spray cut surfaces and associated stem with herbicide mixture.
Stem injection treatment
  • Axe cuts should be made at 5–7cm intervals all around stem (or stems), allowing undamaged bark between cuts.
  • Cuts should be made below first branch and at angle of approximately 30 degrees to stem. Immediately inject up to 1mL of herbicide solution per cut, allowing solution to cover cut surfaces on both bark and tree.

See the Captain Cook tree fact sheet (PDF, 3.3MB) for herbicide control and application rates.

Biological control

  • No known biological control agents.

Legal requirements

  • Captain Cook tree is a restricted invasive plant under the Biosecurity Act 2014.
  • It must not be given away, sold, or released into the environment without a permit.
  • The Act requires everyone to take all reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control. This is called a general biosecurity obligation (GBO).
  • At a local level, each local government must have a biosecurity plan that covers invasive plants and animals in its area. This plan may include actions to be taken on certain species. Some of these actions may be required under local laws. Contact your local government for more information.
Last updated
01 July 2016