Karroo thorn is an adaptable, vigorous shrub or tree that forms dense, thorny thickets and is well suited to Australia’s rangelands. It is fast growing, fire resistant and protected from browsing animals by its thorns. Karroo thorn is usually an evergreen tree, except during droughts or in very dry or cold localities, and grows to a height of 12 m.
Karroo thorn is identified as a threat to biodiversity. Dense thickets reduce agricultural productivity as they suppress the growth of grasses, prevent stock movement (including access to water) and add to the costs of mustering.
It is present in southern Angola, Zambia, Zimbabwee and Mozambique and has been introduced into Libya, Morocco, Myanmar, India, Iraq, Corsica, Portugal, Sicily, Argentina, Bolivia, Chile, Paraguay, Spain and Mauritius. It is considered weedy in South Africa. Plant densities up to 2000 trees per hectare have been recorded in Eastern Cape Province.
As the favourite food of the black rhinoceros, it has been planted in botanic gardens and zoos in south eastern Australia to depict the African landscape. It was first recorded in Australia in Perth during the 1960s, possibly having spread from a residential planting or the Botanic Gardens. It was first recorded in NSW in Dubbo at Taronga Western Plains Zoo, but has since been eradicated. Currently there are no known infestations in NSW or Queensland.
The spread of karroo thorn seed occurs by wind, water and animal droppings. Intentional cultivation by humans has also occurred. Large trees can produce as many as 19 000 seeds per year. These seeds can remain viable in the soil for at least seven years. Seed germination is improved when the outer seed casing is disturbed through means such as fire, passing through the digestive tract of an animal, or gradual weathering over time.
Karroo thorn has paired thorns (up to 10 cm long but can be 25 cm long) that protect the leaves from browsing animals. In some plants the bark is reddish-brown to dark brown or black and rough. Other plants may have bark that is pale greyish-white or greyish-brown and smooth.
Key identification features
Karroo thorn is the most widespread acacia in southern Africa, growing under many soil, climate and altitude conditions, only limited by intense cold or lack of moisture. Its preferred habitat and climate are similar climate to the native grasslands of central New South Wales (NSW) and southern Queensland, giving it the potential to become established over most of subtropical and southern Australia. It is also common in the coastal dune forests of Natal and watercourses of the Karroo region of central Cape Province, indicating further potential to threaten riparian areas in many parts of Australia.
Adapted by AnDi Communications from the CRC for Australian Weed Management Weed Management Guide: Karroo thorn. Reviewed by Rod Ensbey and Peter Gray.
CRC Weed Management Guide
Weed risk assessment – Karroo thorn, The State of Queensland, Department of Employment, Economic Development and Innovation, 2011
Your local council weeds officer will assist with identification, control information and removal of this weed. Infestations can be spread by inappropriate control activities. Early detection and eradication will prevent the spread of this weed.
|All of NSW||1||
State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant