Prickly Acacia, Acacia Hedge, Kangaroo Thorn, Hedge Wattle, Kangaroo Acacia, Prickly Wattle, Paradoxa Wattle

Quick Facts

Kangaroo Thorn (Acacia paradoxa) is a native wattle of mainland south-eastern Australia.
It has been introduced outside of its native Australian range to western Tasmania and south-western Western Australia.
It is a shrub with prickly branches, small phyllodes (leaves) and bright yellow, ball-shaped flowerheads.
It produces hard, long-lived seeds that may be spread as contaminants of vehicles, animals, mud, water and produce.
Kangaroo Thorn can be killed by cutting plants at or below ground level, or by the application of suitable chemical sprays.

What Does It Look Like?

What is it?

Kangaroo Thorn (Acacia paradoxa) is an upright or spreading shrub growing to 1-4 m high with smooth or finely fissured brownish grey bark. The branchlets are vertically ridged and frequently hairy (sometimes hairless). The phyllodes (flattened leaf-stalks that look like, and function as, leaves) are generally straight-sided or slightly curved, narrowed at both ends, 8-20 mm long, usually 2-7 mm wide and hairless or sparsely hairy. The phyllode margins are generally wavy and the main nerve is off-centre. At the base of each phyllode there are two spines (actually stipules) 4-12 mm long that spread widely apart.

The ball-shaped, bright yellow flower heads, on stalks 6-20 mm long, are borne singly (rarely in pairs) at the bases of the phyllodes.

The fruit of Kangaroo Thorn are generally straight-sided, hairy seedpods, 2-7 cm long and 3-5 mm wide. The hard, dark-brown seeds are 4-5 mm long and 2-2.5 mm wide (Maslin 2001; Kodela & Harden 2002; Reid 2008 pers. comm.).

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

Flower colour

Yellow

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

Kangaroo Thorn is found mainly in woodland or open forest on a wide range of soils (Maslin 2001; Parsons & Cuthbertson 2001).

Are there similar species?

Kangaroo Thorn is superficially similar to two native wattles from south-west Western Australia, Acacia idiomorpha and Acacia congesta, but can be distinguished from both of these by the tips of its phyllodes (leaves) which are not stiffly and sharply pointed (Maslin 2001).

One alternative common name for Kangaroo Thorn is Prickly Acacia. This is also the common name for Vachellia nilotica, an introduced wattle from India that is a declared weed in all Australian states and territories. Because it is a shrub or tree that grows to 12 m high with bipinnate (“feathery” or “fern-like”) leaves, Vachellia nilotica will not be confused visually with Kangaroo Thorn. However, the two species could be confused if they are referred to by common names only. It is important to use scientific names wherever possible to emphasise that the widely declared “Prickly Acacia” (Vachellia nilotica) is not Acacia paradoxa (Reid 2008 pers. comm.).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Outside its natural range, Kangaroo Thorn can invade areas of predominantly native vegetation and highly disturbed sites such as cleared paddocks (Western Australian Herbarium 1998-; National Herbarium of Victoria 2007). Clumps of this prickly plant can also provide refuge for pest animals such as rabbits. Its spiny, often dense nature also provides bird nesting sites that are secure from predators (Parsons & Cuthbertson 2001). In common with other wattles, it is likely that the ability to produce hard, long-lived seeds that creates the potential for mass germination in the event of fire or soil disturbance also enables Kangaroo Thorn to naturalise outside its native range (McDonald et al. 2001; Reid 2008, pers. comm.).

How does it spread?

Kangaroo Thorn has been extensively planted as a hedge plant and along roadsides, and naturalisations can originate from seeds of these plantings. The hard, long-lived seeds may be spread as contaminants of vehicles, animals, mud, water and produce (Entwisle et al. 1996; Parsons & Cuthbertson 2001).

What is its history in Australia?

The earliest record of Kangaroo Thorn being available in cultivation in Victoria is in a nursery catalogue published in 1857 (Brookes & Barley 1992). It has been used in most states as a hedge plant and for roadside planting (Parsons & Cuthbertson 2001). It has also been recommended for soil erosion control and for its ornamental qualities (Elliot & Jones 1982). Although it has been listed as a noxious weed in Victoria in the past, it is not currently declared in Victoria (Parsons & Cuthbertson 2001; Melville 2008 pers. comm.).

How To Manage It?

Best practice management

Non-chemical control: Physical removal: Manual removal of Kangaroo Thorn is considered the most practical control method. This can be achieved by dozing or cutting plants at or below ground level, which usually kills them.

Grazing: Browsing by goats considerably reduces plant size and, in time, most plants will die.

Cultivation and management: In agricultural situations the establishment of a competitive pasture will reduce the re-establishment of Kangaroo Thorn seedlings (Parsons & Cuthbertson 2001).

Chemical control: Where chemical control is required, a suitable chemical can be applied as an overall spray to plants in full leaf.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

When does it grow? (lifecycle/growth calendar)

Kangaroo Thorn flowers from July to November (Kodela & Harden 2002). Seedpods are produced mainly from October to January (National Herbarium of Victoria 2007). Seeds probably germinate in autumn and spring and growth is slow in the first year (Parsons & Cuthbertson 2001). Plants can live for several decades (South West Slopes Revegetation Guide undated).

Where Is It Found?

Which states and territories is it found?

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

What areas within states and territories is it found?

Since European settlement, Kangaroo Thorn has been introduced to Tasmania and become naturalised in the west of that state (Maslin 2001; Parsons & Cuthbertson 2001; Buchanan 2005). It is also now considered to be a naturalised introduction in south-western Western Australia where it was formerly considered to be native (Paczkowska & Chapman 2000; Western Australian Herbarium 1998-). Isolated records from a homestead south of Halls Creek in Western Australia and on a station in the Northern Territory south-east of the former location are well north of its known native range and are probably naturalisations and/or planted specimens (National Herbarium of Victoria 2007).

There is also some evidence that it has spread beyond its native range in some parts of Victoria, particularly into coastal areas. It is listed as a native plant that is an environmental weed on the Mornington Peninsula in Victoria and there is also concern about it growing in Bay Road Heathland Sanctuary in the Melbourne bayside suburb of Sandringham. Some consider it part of the original vegetation, but others regard it as being introduced to this area.

It is regarded as invasive in parts of southern New South Wales in grazed native pastures in the Murray Catchment Management Authority area and the South West Slopes region. It can become dominant in these areas as it is not grazed by livestock because of its thorny stems.

Kangaroo Thorn is also regarded as a harmful weed in the ACT that is posing significant environmental or economic problems, and action is thought to be needed to prevent its spread.

It is also naturalised in California, in south-western USA, and is classified as a noxious weed in this state. (Weeds of Australia website).

Where does it originate?

Kangaroo Thorn is native to south-eastern Queensland, eastern New South Wales, Victoria (except the north-west) and south-eastern South Australia. It is possibly native in the Australian Capital Territory (Maslin 2001; AVH 2008). It does not occur in semi-arid areas (Parsons & Cuthbertson 2001).