Mimosa is a branched, spiny, perennial shrub growing to 6 m in height. It forms dense thickets that replace native vegetation in northern Australia’s ecologically and economically valuable wetlands. It tolerates flooding, and can grow along roadsides, watercourses and seasonally inundated wetlands, and on a wide variety of soil types. It has the ability to invade ecologically sensitive areas and threatens indigenous cultural activities, and pastoral and tourism industries. Once mimosa becomes established, it dominates vegetation and is very difficult to control.
Mimosa is a native of tropical America. It grows in moist areas in the humid and sub-humid tropics and has become a very serious weed of Africa, India, Southeast Asia and some Pacific islands.
In Australia the first mimosa plants were brought into the Northern Territory in the early 1890s for the Darwin Botanic Gardens. A large infestation was identified in 1952 on the Adelaide River, 100 km south of Darwin. This infestation was thought to be the primary site for further infestations in the Northern Territory. Sand containing mimosa seed was removed from the area in the 1950s and used at commercial building sites in the north.
Mimosa now occurs on an estimated 85 000 ha of wetlands across northern Australia. It has spread to some of the main river systems in the Top End of Australia (Finniss, Reynolds, Mary Daly, East Alligator and South Alligator) and is also found in the Victoria River in the west and the Phelp River in Arnhem Land. An outbreak was discovered in 2001 near Proserpine in Northern Queensland - outside the projected distribution and indicating that mimosa may be able to survive in areas further south. In late 2009 an isolated patch was identified in a seasonal billabong near Kununnurra in Western Australia.
Mimosa has not been recorded in New South Wales (NSW). Note: it is not the same plant as the commonly-called mimosa bush Vachellia farnesiana which is widespread in parts of NSW.
The spread of mimosa occurs by seed. Large trees can produce up to 220 000 seeds per year. The seed pod segments (containing one seed per segment) float on water or attach to clothing or hair. Seeds can also be carried by water during floods, by animals (e.g. in cattle and horse manure or in mud attached to kangaroos and feral animals) and by humans (e.g. attached to clothing and machinery).
Mimosa has large thorns (5–10 mm long) on the stem and smaller thorns on the branches between the leaves. The greenish stems on young plants become woody with age. Mimosa has a branching taproot which can reach a depth of 1–2 m.
Key identification features
Habitats such as the wetlands of Northern Australia are climatically suited to mimosa.
Adapted by AnDi Communications from the CRC for Australian Weed Management Weed Management Guide: Mimosa.
Reviewed by Peter Gray. Edited by Elissa van Oousterhout, Birgitte Verbeek
Lloyd SG & Vinnicombe TL (2010) Proceedings of the 17th Australasian Weeds Conference pp180-181.
Your local council weeds officer will assist with identification and information on control, removal and eradication of this weed. Infestations can be spread by inappropriate control activities.
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State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant