Weed Alert: Parkinsonia

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Parkinsonia (Parkinsonia aculeata)

World Status | Spread | Identification | Control | Legislation

Parkinsonia is an invasive spiny shrub or small tree that forms impenetrable dense thickets around watercourses such as drainage lines, creeks, dams, rivers and bores. It is adapted to a range of climates and once established is capable of withstanding long periods of heat and drought. Parkinsonia is also known as Jerusalem thorn.

Parkinsonia grows well on open grasslands and rangelands, although wetlands and floodplains are particularly vulnerable to invasion, leading to reduced water flow and availability of surface water, erosion and loss of native habitat. Infestations can also restrict access to land and waterways, degrade pasture, replace native plant species and provide shelter for feral animals.

Originally introduced in the late 1800s as a shade and ornamental tree, parkinsonia has now naturalised throughout most of northern Australia. The largest infestations occur in Queensland, the Northern Territory and northern Western Australia. Small isolated infestations have occurred in South Australia.

In New South Wales (NSW), isolated infestations have been identified in Broken Hill, Walgett, Bourke and the far north western corner of the state. Parkinsonia has the potential to invade the north and central coastal regions and most of western NSW.

World Status

Parkinsonia is native to Central America, the Caribbean, southern USA, Mexico and northern South America.

It has been introduced to many parts of the world and has become an invasive weed of South Africa, the Mediterranean, tropical Africa, south-western Asia, India and the Pacific Islands. Parkinsonia has also become invasive in parts of its native range including Mexico and southern USA.

Spread

Parkinsonia reproduces by seed. Water movement is responsible for most of its spread as seed pods can float and be carried large distances by floodwaters.

A mature tree usually produces around 5000 seeds per year. Seeds have a hard, thick coat and can remain dormant in the soil for a number of years. Dormancy is normally broken by wet and warm to hot conditions, and is then usually followed by a mass germination event.

Spread can also occur through movement of contaminated sand or soil from infested sites.

Identification

Parkinsonia is a single- or multi-stemmed shrub or small tree that can grow up to 8 m high.

Key identification features

• Stems are green, smooth and slender, slightly zig-zagged and drooping.
• Each leaf stalk is green and flat, up to 30 cm long and 2–3 mm wide, with many small (4–10 mm) oblong leaflets staggered along each side.
• Spines are sharp, 5–15 mm long and grow from the leaf nodes.
• Fragrant flowers are about 2 cm across and 5-petalled, with four petals yellow and one erect orange or orange-spotted petal. Each flower stalk is 5–20 cm long and has 8–12 flowers.
• Seed pods are hairless, up to 10 cm long, leathery and straw-coloured when ripe. They are straight with pointy ends and have constrictions between the seeds. Each pod usually contains 1–4 seeds, but occasionally up to 11.
• Seeds are oblong, 8–10 mm long and olive to brown in colour.

Control

If you suspect you have found parkinsonia you should contact your local council weeds officer who will assist with identification, removal and eradication.

A range of control options are available for parkinsonia. A suitable control program should be tailored to suit the landscape and size of the infestation.

Legislation

Parkinsonia is a Class 2 Regionally Prohibited Weed in parts of NSW under the Noxious Weeds Act 1993. It must be eradicated and land must be kept free of the plant. As a notifiable weed, all outbreaks must be reported to the local council within 24 hours, and the plant is prohibited from sale in NSW.

Acknowledgments

Adapted from CRC Weed Management Guide (2003) Parkinsonia (Parkinsonia aculeata)

Reviewed by: Peter Gray; Edited by: Elissa van Oosterhout

References

Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK