Quick Facts

Quick facts

• Giraffe Thorn (Vachellia erioloba) is a long-lived large shrub or small tree from southern Africa that reproduces mainly by seeds.
• It starts to flower when about 10 years old and is spread when the seeds are eaten by animals and dispersed.
• It displaces preferred vegetation and is potentially very highly invasive in Australia.
• Predictions indicate that it could occupy large areas of inland and northern Australia if allowed to spread.

What Does It Look Like?

What is it?

Giraffe Thorn (Vachellia erioloba) [as Acacia erioloba] is a long-lived large shrub or small tree with an upright habit usually growing 2–6 m tall and spreading up 10 m across. Very old trees may reach 20 m in height. Old branches have rough, deeply-furrowed, dark grey to blackish-brown bark and often become considerably contorted. Young stems usually have a zig-zagging nature, and are reddish-brown and shiny. Prominent thorns, up to 6 cm long and often with swollen bases, are produced in pairs at the base of each leaf. These are almost straight, and whitish or brown. Leaves are medium green or bluish-green and up to 6 cm long. Each leaf consists of 1–5 pairs of branchlets each bearing 8–18 pairs of small oblong or elongated leaflets.

The 'wattle-like' flowers are borne in small, bright yellow, rounded and fluffy clusters about 8–15 mm across and they are borne singly in the leaf forks.

The fruit are large woody pods, 11–12 cm long and 4–6 cm across, that have a covering of velvety hairs giving them a greyish appearance. These pods are variously described as being half-moon shaped, kidney-shaped, ear-shaped or roughly sickle-shaped. Unlike other Vachellia [as Acacia] species the pods do not split open, even at maturity, but are consumed by animals. They are spongy inside, and contain several reddish-brown coloured seeds (Faithful & Blood 2001; Navie 2004).

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

Flower colour

Yellow

Growth form (weed type/habit)

Tree

Where it currently grows? Preferred habitat

Giraffe Thorn prefers open woodlands, grasslands and overgrazed pastures in semi-arid, tropical and subtropical environments (Navie 2004).

It is a long-lived plant that grows on sand in areas with an annual rainfall of less than 40 mm to 900 mm, and tolerates hot summer temperatures and severe frosts. In very dry areas it occurs along watercourses or where underground water is present. The taproot can descend to 60 m, providing access to deep ground water (Dlamini 2007).

Are there similar species?

Giraffe Thorn and Karroo Thorn (Acacia karroo) can be distinguished from all Australian native Acacias by the presence of both feathery foliage and sharp spines over 15 mm long. However, two other Acacia species found in Australia have these characteristics. Prickly Acacia (Vachellia nilotica) [as Acacia nilotica subsp. indica] is a native of India, has naturalised in tropical Queensland and parts of the Northern Territory and South Australia and is a Weed of National Significance. It has pods that are usually markedly constricted between the seeds, like a necklace. Mimosa Bush (Vachellia farnesiana) [as Acacia farnesiana] is widespread in northern Australia and is believed to have been introduced from Central America via the Philippines before European settlement. Its leaves have a gland on the leaf stalk before the first side branches of the leaf (Faithfull & Blood 2004).

Karroo Thorn (Vachellia karroo) [as Acacia karroo] is also a thorny plant with feathery leaves and has fluffy bright yellow flowers in small globular clusters in the leaf forks. The fruit of Karroo Thorn are larger and more elongated than the fruit of Giraffe Thorn. They are sickle-shaped or curved, smooth and hairless, have slight constrictions between the seeds, and turn dark brown as they mature (Navie 2004).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Giraffe Thorn is a competitive species that can displace preferred vegetation. It has been assessed as being potentially very highly invasive in Australia. Climate predictions indicate that it could occupy large areas of inland and northern Australia if allowed to spread (Faithfull & Blood 2004).

How does it spread?

Giraffe Thorn reproduces mainly by seeds, which are most probably dispersed by large animals (which eat the fruit), and by water movement (Navie 2004).

What is its history in Australia?

Giraffe Thorn is present in Australia but has not yet naturalised.

How To Manage It?

Best practice management

There is no information available on control of Giraffe Thorn. It can be assumed that the same control methods used for the closely related Karroo Thorn can be used on Giraffe Thorn (see https://profiles.ala.org.au/opus/weeds-australia/profile/Vachellia%20karroo)

If you live in Victoria and discover Giraffe Thorn on your property you should report it to Agriculture Victoria and they will come and remove the plant (https://agriculture.vic.gov.au/biosecurity/weeds/state-prohibited-weeds/karoo-and-giraffe-thorn).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

In a study in Botswana, Giraffe Thorn flowered at the end of the cool dry season and produced new leaves at the same time as flowers. Temperature and daylength appeared to be the most probable triggers for the production of new leaves and flowers (Sekhwela & Yates 2007).

Seeds germinate under suitable conditions after passing through the digestive tract of large grazing mammals, which disperse the seed in their dung. Giraffe Thorn trees start to flower when about 10 years old (Faithfull & Blood 2004; Dlamini 2007).

Where Is It Found?

Which states and territories is it found?

Not naturalised in Australian state or territory.

What areas within states and territories is it found?

Giraffe Thorn is present in Australia but has not yet naturalised. Some sources suggest that it has naturalised in the Australian Capital Territory, but this has proven not to be the case (Navie 2004; Australian National Herbarium 2008; AVH 2008; Lepschi et al. 2008).

Where does it originate?

Giraffe Thorn is widely distributed in southern Africa (Dlamini 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

QLD, 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

Vachellia erioloba

Other scientific names (synonyms)?

Acacia erioloba E.Mey.

Does it have other known common name(s)?

Camel Thorn, Camelthorn, Transvaal Camelthorn, Camelthorn Acacia, Camel-thorn Acacia, Camel Thorn Acacia, Green Camel Thorn, Mimosa, African Acacia, Kameeldoring