Name:
Parkinsonia
Botanical Name:
Parkinsonia aculeata
Description
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.
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.
For further information and assistance with identification of Parkinsonia contact the herbarium in your state or territory.
Distribution:
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 is been estimated that at least 800 000 hectares of land are infested with this species.
Habit:
Shrub, Tree
Key points:
- Parkinsonia (Parkinsonia aculeata) is a fast grower and can flower as early as the summer of its second year of growth.
- It is a threat to rangelands and wetlands
- 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.
How it spreads:
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. Both seeds and pods can be dispersed on unclean machinery, for example, in mud.
Where it grows:
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.
Flower colour:
Yellow
Distribution map:
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.
Plants can form dense impenetrable thickets on rangelands and wetlands, making areas of land inaccessible for people and animals. Seed pods float and are easily spread by water. 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. Parkinsonia infestations provide refuges for feral animals especially pigs.
Origin:
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.
History:
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.
