Neem tree

Native to north-eastern India, neem tree is a fast-growing evergreen that has been introduced and established throughout Australia's tropics and subtropics.

Neem is used to produce insecticide, and was planted across northern Australia for this reason. However, it has escaped cultivation and could become more widespread across north-western Queensland. In dense stands, it could have adverse effects on native plants and animals.

Neem tree is not a prohibited or restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Azadirachta indica

Other names

Neem, Indian lilac, white cedar, margosa, nimtree, margosier

Description

  • Fast-growing evergreen generally 15-20m tall, with crown diameter up to 20m.
  • Leaves are evergreen, alternate, 20-40cm long, with 2-30 dark green, serrated leaflets, each about 3-8cm long.
  • Petioles are 70-90mm long.
  • Flowers are small, cream, perfumed, about 1cm in diameter, with 5 petals, in clusters 15-25cm long comprising 150-250 flowers.
  • Fruits are olive-like, 1-3cm in diameter, yellow when ripe, varying from elongated oval to roundish, with sweet pulp enclosing single seed.
  • Seeds are brown, elongated, 1.5-2.5cm.
  • Roots are strong with a deep tap root, extensive lateral system.
  • Suckers can be produced following damage to roots.

Habitat

  • Prefers deep, permeable, sandy soils in subarid and subhumid areas with tropical and subtropical climates.

Distribution in Queensland

  • Planted throughout Queensland.
  • Grow wild in sandy riverbeds of Gulf region.

Life cycle

  • Fruiting starts when plants are 2-5 years old.
  • Can live up to 200 years.

Affected animals

  • Fish; tadpoles ; native insects

Impacts

Environmental

  • Decomposing plant matter can affect aquatic life such as fish and tadpoles.
  • Can reduce native insect populations.
  • Reduces diversity and abundance of native species when growing in dense stands.

How it is spread

  • Seeds spread by birds and bats.

Control

Physical control

  • Hand-pull seedlings of individual plants.
  • Remove roots with care to prevent regrowth.
  • Cut down to stump and treat with herbicide immediately to prevent suckering from roots.

Herbicide control

  • No herbicide is currently registered in Queensland. However, an off-label use permit (Permit No. PER11463) allows use of various herbicides to control environmental weeds in non-agricultural areas, bushland and forests.
  • Glyphosate 360 1:1 water would cover most situations (read label carefully and follow as directed).
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.

Biological control

  • No known biological control agents.

Legal requirements

  • Neem tree is not a prohibited or restricted invasive plant under the Biosecurity Act 2014. However, by law, everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control.
  • Local governments must have a biosecurity plan that covers invasive plants and animals in their 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.

More information

Contact us

Call your local government office, or Biosecurity Queensland on 13 25 23.

Last updated
01 July 2016