Quick Facts

Quick facts

• Parkinsonia (Parkinsonia aculeata) is a native plant of the Americas that was introduced into Australia as an ornamental plant in the 19th century.
• Parkinsonia is considered a WONS in Australia and is present on almost one million hectares of the mainland.
• It forms dense prickly thickets along watercourse and makes land inaccessible.
• Parkinsonia is a fast grower and can flower as early as the summer of its second year of growth.
• Seed pods float and are easily spread by water.
• It is a threat to rangelands and wetlands and in particular flood prone country is susceptible.
• Use of chemicals produces less regrowth than if mechanical means are used
• Control measures always need to be followed up as some trees may be missed during initial control and regrowth can occur from seeds and roots.

What Does It Look Like?

What is it?

Parkinsonia (Parkinsonia aculeata) is a spreading, much-branched shrub or tree to 8 or rarely 10 m tall. It has a deep taproot and extensive surface roots. Its stems are slender, drooping and tend to zig-zag, with thorns 5-20 mm long. Young plants are usually single thorny stems (Deveze 2004)

Parkinsonia leaves consist of a flat, green leaf stalk up to 300 mm long and 2-3 mm wide with numerous small (4-10 mm) green oblong leaflets staggered along both sides. The leaf base is protected by sharp, recurved spines, 5-15 mm long, which persist in older branches.

The fragrant flowers are up to 20 mm in diameter, with five petals, and predominantly yellow. The top petal either has orange spots or turns completely orange. Each flower grows on a long, slender, drooping stalk arising from leaf joints in groups of 8 to 12.

The fruit is an elongate, almost straight pod about 3-13 cm long and 3.5-8 mm wide and narrows at both ends; it is somewhat flattened and usually has pronounced constrictions between each of the seeds and at maturity is a pale brown or yellow-brown. Seeds, of which there are usually just 2-4 per fruit pod, but sometimes up to 8, are oval or oblong in shape, 9-15 mm long, 3-4 mm wide, and are olive green to brown (Ross 1998; CRC 2003; Deveze 2004).

For further information and assistance with identification of Parkinsonia contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Shrub, Tree

Where it currently grows? Preferred habitat

Commonly on seasonally flooded sites but also around dams and bores, as well as stream banks and floodplains; on sand to clay soils. It inhabits pastures, roadsides, grasslands, open woodland and rangelands (Deveze 2004).

Are there similar species?

Parkinsonia is most likely to be mistaken for other thorny shrubs and trees such as Prickly Acacia (Vachellia nilotica) [as Acacia nilotica], Mesquite (Prosopis pallida) [as Prosopis limensis] and Needle Bush (Vachellia farnesiana) [as Acacia farnesiana] and Mimosa (Mimosa pigra). Parkinsonia has tiny oblong leaflets on a flattened leaf stalk, whereas the other species have fernlike leaves. The bark of Parkinsonia is also smooth and green (Deveze 2004).

Why Is It A Weed?

What are its impacts?

Parkinsonia is a Weed of National Significance. It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. Parkinsonia has the potential to invade more than three quarters of mainland Australia.

Agriculture: Plants can form dense impenetrable thickets on rangelands and wetlands, making areas of land inaccessible for people and animals. Thickets can be up to several kilometres across. Cattle are difficult to muster in paddocks where Parkinsonia infestations are thick. Access to watering points is impaired by the thickets which also shade out valuable pastures and displaces native vegetation when left untreated. Parkinsonia can dam watercourses, cause erosion, and lower water tables. A very hardy plant that can withstand long dry spells. Seeds remain viable for many years (Smith 2002). Parkinsonia infestations provide refuges for feral animals especially pigs (CRC 2003; Deveze 2004).

How does it spread?

Parkinsonia produces abundant seed, a typically mature plant producing about 5 000 seeds per year and large specimens more than 13 000. They fall within the pods which can be widely dispersed in moving water. The pods are relatively unpalatable and so spread by animals feeding on them is probably a minor method of dispersal (CRC 2003). Both seeds and pods can be dispersed on unclean machinery, for example, in mud.

What is its history in Australia?

Parkinsonia is believed to have been introduced into Australia in the 1890s and early 1900s for use as an ornamental in towns and (perhaps subsequently) as a shade tree around homesteads and bores in northern Australia (Smith 2002; Deveze 2004).

How To Manage It?

Best practice management

The economic costs of control are high once Parkinsonia becomes established. The prevention of spread within and between catchments, early detection and control of small manageable outbreaks are thus high priorities when considering management strategies (CRC 2003).

Soil or sand which could contain Parkinsonia seeds should not be removed from infested areas. Any transport or machinery used in infested areas should be thoroughly cleaned before moving to other areas. Because water is responsible for much of the spread of Parkinsonia, outbreaks on watercourses, particularly in upper catchments, are a priority for control (CRC 2003).

Research into Parkinsonia control commenced in the 1950s and has been ongoing. The results from this research have shown that seedlings are particularly susceptible to different forms of control, especially fire, drought or inundation, soon after germination. An integrated approach using several weed management techniques (e.g. mechanical and chemical control, fire) is the most effective way to deal with dense infestations of Parkinsonia. However, the characteristics of the infestation (e.g. size, density, location, position within the catchment) and the availability of resources will determine the exact course that control should take.

Chemical control: There is a wide range of herbicides registered for Parkinsonia control, with several different application methods. Herbicides are useful for controlling dense high priority infestations but otherwise may be too expensive for widespread use. Particular care with herbicides should be taken near waterways (CRC 2003). Herbicides can be applied in a number of ways including aerial spraying and manual foliar application. Basal bark spraying and cut stump application can also be effective. For general information of the use of chemicals please visit the Australian Pesticides and Veterinary Medicines Authority at http://www.apvma.gov.au 

Non-chemical control: Mechanical removal, such as hand pulling for small plants and bulldozing or chain pulling for larger plants, can be effective as long as roots are removed to a depth of 200 mm to prevent regrowth. Mechanical removal is more cost-effective that chemical control over large areas. However, it is not advised for river banks due to the potential for erosion and damage to non-target species. Follow-up is essential to treat seedlings (which can germinate prolifically in the disturbed ground) and any remaining adult plants (CRC 2003).

Fire kills seedlings and seeds on the surface and is an excellent form of follow-up control after mechanical or chemical control. With mature plants, however, the results are mixed. The Queensland Department of Natural Resources and Mines is currently researching which fire regimes give maximum kill rates of mature Parkinsonia in central Queensland (CRC 2003).

Biological control: Parkinsonia has also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. Biological control has yet to show any major successes but research is continuing (CRC 2003).

For more detailed information on control strategies see Deveze (2004).

For further information see the Parkinsonia Best Practice Manual (available at https://www.weeds.org.au/WoNS/Parkinsonia)

Does it have a biological control agent?

YES. Five biocontrol agents released: including seed-feeding beetles (Penthobruchus germaini and Mimosetes ulkei), a leaf bug (Rhinacloa callicrates) and leaf-feeding moths Eueupithecia cisplatensis,  Eueupithecia vollonoides) (Harvey, et al 2023).

When does it grow? (lifecycle/growth calendar)

Parkinsonia plants grow quickly and are known to flower as early as the summer of their second year.

Established plants may bear flower and fruit at anytime of the year but, across Australia, flowering is generally in the warmer months after winter (from as early as July to the end of January) with pods developing soon after (October to April). Seeds germinate in response to prolonged periods (several days worth) of rain, with most germination occurring (CRC 2003).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, SA, WA

What areas within states and territories is it found?

In Australia most infestations occur in coastal, central and western Queensland, central and northern parts of the Northern Territory, and the Pilbara and Kimberley regions of Western Australia. Isolated populations have been recorded in South Australia and western New South Wales. It has been estimated that at least 800 000 hectares of land are infested with this species (CRC 2003).

Where does it originate?

Parkinsonia is native to tropical regions of the Americas, from the southern regions of the United States to northern South America (e.g. Colombia, Costa Rica, Guatemala, Panama and Peru).

It has been introduced to some South American countries (including mainland Ecuador and El Salvador) and many other regions, including tropical Africa, the Middle East, Italy, Cyprus, India, Pakistan, Thailand, Cambodia, Vietnam, Indonesia, many Pacific islands (e.g. Hawaii, Tahiti) and Australia.

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

YES

Where is it a declared weed?

ACT, NSW, NT, QLD, SA, TAS, VIC, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Parkinsonia aculeata

Other scientific names (synonyms)?

Does it have other known common name(s)?

Jerusalem Thorn, Jelly Bean Tree, Horse Bean