Parkinsonia

Thought to be native to tropical America, parkinsonia is a small, hairless tree that has spread throughout the world as an ornamental and shade tree. It forms dense, thorny thickets along watercourses, restricts stock access, and reduces pasture production. Large parkinsonia infestations exist in Queensland's Gulf of Carpentaria and Fitzroy regions.

Parkinsonia is a restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Parkinsonia aculeata

Description

  • Small, hairless tree up to 10m tall.
  • Branches are slender, zigzag shaped, with sharp spines.
  • Leaves have a short, spine-tipped stalk.
  • Leaf branches are 20-40cm long.
  • Flowers are yellow, fragrant, 5-petalled, each on a long, slender, drooping stalk.
  • Seed pods are pencil-like, 5-10cm long, constricted between seeds.
  • Seeds are oval, about 15mm long, with thick, extremely hard coat.

Habitat

  • Occurs most abundantly on flood plains but adaptable to a wide range of soil types.

Distribution in Queensland

  • Found along watercourses in subhumid and semi-arid areas of Queensland.
  • Infestations in Gulf of Carpentaria and Fitzroy catchment are up to several kilometres across.

Life cycle

  • Flowers in early summer of second or third year, then exploits variable seasonal conditions.
  • Pods mature in late summer and are readily dispersed by floodwaters.
  • Seeds remain viable until favourable conditions occur.

Impacts

Environmental

  • Forms dense, often impenetrable, thorny thickets along watercourses and bore drains.
  • Flooded country is particularly susceptible to invasion from floating seeds.
  • Provides haven for feral pigs, which prey on livestock, damage crops, and degrade environment.

Economic

  • Reduces pasture production.
  • Restricts stock access to drinking water and makes mustering almost impossible.

How it is spread

  • Spread primarily by floodwaters.
  • Minor spread possible by mud sticking to vehicles and animals.

Control


Physical control

Fire
  • Best results obtained from slow-moving grassfires that maintain heat around the base of plants for as long as possible.
  • Seedlings are most susceptible to fire, but moderate to high kills of larger plants can occur under the above conditions.
  • Spelling before burning to build a fuel load may be necessary. Controlling grazing pressure afterwards to re-establish a competitive pasture is recommended.

Mechanical control

  • Initial clearing by stickraking, blade ploughing or ripping is effective, however:
    • it should be restricted to reasonably level areas away from watercourses
    • clearing will hasten seed germination, necessitating follow-up control either mechanically or chemically.

Herbicide control

Aerial application
  • Aerial application is undertaken using purpose-built applicators attached to aircraft. This technique is useful for dense, strategic infestations, although it may be expensive on a broad scale and needs to be undertaken in accord with vegetation management legislation.
Foliar spray
  • This is an effective control method for seedlings up to 1.5m tall. Spray leaf and stems to point of run-off. A wetting agent must be used.
Basal bark spray
  • For stems up to 15cm in diameter, carefully spray around base of plant to 30cm above ground level. Larger trees may be controlled by spraying to a greater height, up to 100cm above ground level.
  • Plants should be actively growing and preferably flowering. Field experience has shown that good soil moisture is essential for effective control.
  • Because parkinsonia-infested areas are often subject to flooding, take care to ensure mud and flood debris does not prevent spray penetration to the bark. Trunks may need to be cleared before spraying.
Cut stump treatment
  • Can be performed year-round. Cut stems off horizontally as close to ground as possible. Immediately (within 15 seconds) swab or spray cut surface and associated stem with herbicide mixture.
Soil application
  • Use 1 dose of herbicide per metre of tree height. Place doses close to tree trunk, either with spot gun on clear, bare ground, or underground with ground injector. Rain or sufficient soil moisture is required before herbicide is taken up by plant.
  • Do not use near watercourses or within a distance equal to at least twice the height of desirable trees.

See the Parkinsonia fact sheet (PDF, 4.1MB) for herbicide control and application rates.

Biological control

  • Four species of insects have been introduced.
  • Both Penthobruchus germaini and Mimosetes ulkei are seed beetles that attack only parkinsonia and whose larvae destroy mature parkinsonia seeds. Penthobruchus germaini may be giving some control.
  • Parkinsonia leaf bug Rhinacloa callicrates is a small green bug imported from the USA.
  • A leaf-feed looper (Eueupithecia cisplatensis), from Argentina.
  • Naturally occurring fungal pathogens have been identified as causing dieback in many infestations of parkinsonia across northern Australia. Studies are continuing regarding the use of these pathogens as biological control tools.

Legal requirements

  • Parkinsonia 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.

More information