Parkinsonia (Parkinsonia aculeata)

Also known as: Jerusalem thorn

Parkinsonia is a spiny shrub or small tree with yellow flowers. It forms dense, impenetrable thickets especially around watercourses, streams and water bodies.

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How does this weed affect you?

Parkinsonia forms dense, spiny thickets that restrict access to land and waterways. It also:

• makes mustering difficult
• reduces water flows and lowers the water table
• reduces livestock access to water
• reduces pasture productivity
• reduces land values
• outcompetes native plants
• reduces food and habitat for native animals
• causes erosion
• provides shelter for feral animals, especially pigs.

What does it look like?

Parkinsonia is a single or multi-stemmed shrub or small tree up to 8 m tall.

Leaves:

The leaves are made up of a flat green leaf stalk up to 30 cm long and 2–3 mm wide. Along the stalk are 10–40 pairs of small leaflets that are:

• green
• 4–10 mm long
• oblong
• easily detached.

Spines are:

• 5–15 mm long
• sharp and curved backwards
• at the leaf nodes.

Flowers:

• have 5 petals including 4 yellow petals and one orange or orange-spotted petal
• are 2 cm wide and on stalks 5–20 cm long
• are fragrant
• grow in clusters of 8–12 flowers on a stem
• present from summer to early autumn.

Seed pods are:

• leathery and straw-coloured when ripe
• hairless
• up to 10 cm long
• straight with pointy ends
• constricted between the seeds
• normally with 1–4 seeds but can contain up to 11 seeds.

Seeds are:

• 8–10 mm long
• olive to brown
• oblong with a hard, thick coat.

Stems are:

• green smooth and slender
• slightly zigzag shaped and drooping
• straw coloured at the base of old trees.

Similar looking plants

There are several similar looking prickly bushes. The main difference is that Parkinsonia is the only species that has a flattened leaf stalk. The other species all have fern-like leaves with larger leaflets. Similar plants include:

• Prickly acacia (Vachellia nilotica) which has ball-shaped golden yellow flowers.
• Mesquites (Prosopis spp.) which have cylindrical greenish-cream flowers, up to 8 cm long.
• Mimosa bush (Vachellia farnesiana) which has ball-shaped, golden yellow or orange flowers.
• Karroo thorn (Vachellia karroo) which has much larger spines, up to 25 cm long.

Where is it found?

There have been isolated infestations in and around Broken Hill, Walgett, Bourke and the far north-western corner of NSW. In 2020 it was found near Brewarrina and these plants are under an eradication program. Parkinsonia could invade most of western NSW particularly along riverine areas. It could also invade the northern and central coastal areas.

In the late 1800s, it was brought to Australia as a shade and ornamental tree. It has naturalised throughout most of northern Australia.

Parkinsonia is native to the Americas and the Caribbean. It is a weed in Africa, the Mediterranean, south-western Asia, India and the Pacific Islands.

What type of environment does it grow in?

Parkinsonia grows in arid to wet-dry tropical climates with rainfall from 250 to 1400 mm/year.

It is a hardy plant and tolerates:

• drought conditions
• seasonal waterlogging
• a wide range of soil types from sandy to heavy clays
• saline, alkaline and acid soils
• mild frosts
• very high temperatures.

Wetlands and floodplains are very susceptible to invasion. Parkinsonia also grows well on open grasslands and rangelands.

Maps and records

• Recorded presence of Parkinsonia during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Parkinsonia plants usually produce about 5000 seeds/year. Seed production starts when trees are 2 or 3 years old. 

Seeds have a hard, thick coat and can remain dormant in or on the soil surface. In most locations, seeds are only viable for up to one year. Though some have been recorded viable after being dormant for 4 years. Fires can cause germination. Mass germination occurs in wet and warm to hot conditions.

Many seeds fall close to the parent plant. However, seeds are spread by:

• water flow and flood waters which can move the floating pods and seeds large distances
• birds, camels and other animals that eat the seeds
• contaminated sand or soil
• mud attached to machinery, vehicles, footwear or animals.

References

CRC for Australian Weed Management (2003) Weed Management Guide: Parkinsonia – Parkinsonia aculeata.

Hosking, J.R., Sainty, G.R., Jacobs, S.W.L., & Dellow, L.L. (in prep). The Australian WeedBOOK.

Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved: 20 January 2021 from https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Parkinsonia~aculeata

Queensland Government. (2020). Identification of prickle bushes. Retrieved 13 August 2020 from: https://www.daf.qld.gov.au/__data/assets/pdf_file/0006/72195/IPA-Identification-Prickle-Bushes-PP40.pdf 

van Klinken, R. D., Campbell, S. D., Heard, T. A., McKenzie, J., & March, N. (2009). The Biology of Australian Weeds: 54.'Parkinsonia aculeata'L. Plant Protection Quarterly, 24(3), 100.

More information

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Control

If you suspect you have found Parkinsonia contact your local council weeds officer. They 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. Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

To tackle Parkinsonia:

• prioritise infestations on watercourses, especially in upper catchments
• kill mature plants to stop seed production
• use a control method suitable for the landscape and size of the infestation
• look for and control flushes of seedlings after warm, wet conditions
• keep checking for new seedlings for several years because the seeds can lie dormant in the soil.

Prevention

Avoid moving soil from infested areas. Clean machinery after use in areas with Parkinsonia. Hold stock in a quarantine paddock before moving them from areas with Parkinsonia to uninfested areas.

Physical removal

By hand

Hand pull small Parkinsonia plants or grub them out with a mattock.

By machine

When: At the start of the dry season when the infestation first becomes accessible to heavy machinery but there is still moisture in the soil.

Follow-up: With chemical control, fire or careful machine operations to treat survivors, regrowth and new seedlings.

Mechanical control of large infestations may be more cost-effective than chemical control, especially on flat even ground. Parkinsonia can be bulldozed, stick-raked, blade ploughed or chain pulled. Remove the roots to about 200 mm deep to prevent them from reshooting with multiple stems. Multi-stemmed plants can be more difficult to remove than the original plants.

Permits may be required if native species could be affected by the Parkinsonia control effort. Machinery is not recommended for controlling Parkinsonia along river banks as this may cause erosion and damage to non-target species.

Where practical sow perennial pastures to prevent Parkinsonia seedlings from establishing.

Chemical control

Spot application

Spot applications to the soil are best when the plants are actively growing and the soil is moist. Spear applicators are best if there is leaf litter or pasture around the target plants.

Basal barking

Basal barking can be used for plants with stems up to 5 cm in diameter at the base. Liberally spray the bark all the way around the stem from ground level to 30 cm high. Wet thoroughly to the point of runoff. Apply to dry stems as wet stems can repel the mixture. 

Best results are achieved when soil is moist and plants are actively growing.

Cut stump method

Cut trunks or stems less than 15 cm above the ground. Apply herbicide to the cut and the sides of the stump immediately.

Herbicide options

See Using herbicides for more information.

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Hexazinone 250 g/L (Velpar® L)
Rate: 4 mL per spot
Comments: One spot per bush up to 5 m tall.
Withholding period: No stated withholding period.
Herbicide group: C, Inhibitors of photosynthesis at photosystem II (PS II inhibitors)
Resistance risk: Moderate

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Hexazinone 250 g/L (Velpar® L)
Rate: 1 mL per spot
Comments: One spot per bush up to 1 m tall. Do not use near desirable plants.
Withholding period: No stated withholding period.
Herbicide group: C, Inhibitors of photosynthesis at photosystem II (PS II inhibitors)
Resistance risk: Moderate

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Picloram 44.7 g/L + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump/stem injection application. Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm .
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Triclopyr 240 g/L + Picloram 120 g/L (Access™ )
Rate: 1.0 L in 60 L of diesel (or biodiesel such as Biosafe).
Comments: Basal bark application for plants with stems up to 5 cm diameter at the base. Cut stump application can be used for plants with stems up to and in excess of 5 cm diameter at the base. See label for information about biodiesel.
Withholding period: Nil
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW	Prohibition on certain dealings Must not be imported into the state, sold, bartered, exchanged or offered for sale.
All of NSW Parkinsonia Control Zone: Whole of NSW	Control Order Parkinsonia Control Zone (Whole of NSW): Owners and occupiers of land on which there is parkinsonia must notify the local control authority of new infestations; immediately destroy the plants; ensure subsequent generations are destroyed; and ensure the land is kept free of the plant. A person who deals with a carrier of parkinsonia must ensure the plant (and any seed and propagules) is not moved from the land; and immediately notify the local control authority of the presence of the plant.

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Reviewed 2022