Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species (including this one) should retain the name Acacia, whilst other sections of the genus should be transferred to the genera Acaciella, Mariosousa, Senegalia and Vachellia[].

Common Name: Dune Wattle

General Information

Acacia ligulata is a dense, rounded multi-stemmed shrub or a small tree, usually growing 1 - 3 metres tall but occasionally reaching 5 metres[, ]. Although it produces true leaves as a seedling, like most members of this section of the genus, the mature plant does not have true leaves but has leaf-like flattened stems called phyllodes[].
The plant is harvested from the wild for local use as a food and medicine. Tolerant of some of the hottest and driest conditions in Australia, the plant can be used as a soil stabilizer and low windbreak.
The plant's ease of regeneration suggests it has the potential of becoming a weed under favourable conditions[].

Known Hazards

The seed of many Acacia species, including this one, is edible and highly nutritious, and can be eaten safely as a fairly major part of the diet. Not all species are edible, however, and some can contain moderate levels of toxins[]. Especially when harvesting from the wild, especial care should be taken to ensure correct identification of any plants harvested for food[].
Especially in times of drought, many Acacia species can concentrate high levels of the toxin Hydrogen cyanide in their foliage, making them dangerous for herbivores to eat.

Botanical References

Range

Australia - all mainland States

Habitat

Widespread in arid regions, usually growing in sand, often in mulga and mallee communities; at elevations up to 700 metres[]. Common on sand dunes but also occurs on flood and erosion plains, lower hill slopes, and on the lunettes fringing lakes[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Shrub
Height	3.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

A plant of arid regions in the temperate to subtropical zones and just entering into the tropics of southern and central Australia, where it is found at elevations up to 700 metres. It succeeds in some of the hottest and driest regions of Australia. It grows best in areas where annual daytime temperatures are within the range 18 - 33°c, but can tolerate 8 - 42°c[, ]. When dormant, the plant can survive temperatures down to about -5°c, but young growth is more tender and can be severely damaged at -1°c[]. It prefers a mean annual rainfall in the range 125 - 225mm, but tolerates 100 - 700mm[, ]. It withstands a dry season of 5 - 11 months[].
Requires a sunny position in a well-drained soil[]. Tolerates a wide range of soil textures, succeeding even where fertility is very low[]. Tolerant of moderate levels of salt in the soil[]. Prefers a pH in the range 7 - 8, tolerating 6.5 - 8.5[]. Established plants are very drought tolerant[].
The plant's ease of regeneration suggests it has the potential of becoming a weed under favourable conditions[].
A fast-growing plant when young[].
Plants can spread by suckers and will re-shoot from a damaged crown[].
Although usually top-killed by fire, the plant can resprout from the base and any seeds in the soil will be stimulated into germinating - in central Australia the plant germinates so freely that it is considered to be a fire-weed[].
The seeds of most acacia species can be quickly and efficiently harvested at full maturity without the need for any specialised equipment. Small seed-bearing branches can be cut and beaten on sheets, or bushes can be beaten or shaken directly onto large sheets[]. Mature seeds of this species remain attached within the pods for several weeks following dehiscence. The pods, however, especially on plants in Central Australia, can mature unevenly and consequently much effort can be required to collect large amounts of seed[]..
This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].
This species is closely related to Acacia bivenosa and in places the two species seem to hybridize[].

Edible Uses

Seed - cooked[]. The seeds can be ground and eaten but undesirable side-effects have been observed[, ]. The seedpods are up to 90mm long and 5 - 9mm wide, with shiny brown, oblong-elliptic seeds normally 4 - 6mm long[].
Acacia seeds are highly nutritious and contain around 26% protein, 26% available carbohydrate, 32% fibre and 9% fat. The fat content is higher than most legumes with the aril providing the bulk of fatty acids present. These fatty acids are largely unsaturated. The energy content is high in all species tested, averaging 1480 ±270 kJ per 100g. The seeds are low glycaemic index foods - the starch is digested and absorbed very slowly, producing a small, but sustained rise in blood glucose and so delaying the onset of exhaustion in prolonged exercise[].

The ground seed can be used to produce a high quality, caffeine-free coffee-like beverage[].

Gum[].

Medicinal

The leaves and branches of this species are used traditionally by N.T. aborigines as a diaphoretic for several complaints, including certain disturbances of the nervous system[].

Its ash is favoured for use with pituri (Duboisia hopwoodii) as a narcotic. The smoke from its leaves is considered to have benefits for a range of illnesses and a decoction of its bark is used as a medicinal wash[].

The bark of all Acacia species contains greater or lesser quantities of tannins and are astringent. Astringents are often used medicinally - taken internally, for example. they are used in the treatment of diarrhoea and dysentery, and can also be helpful in cases of internal bleeding. Applied externally, often as a wash, they are used to treat wounds and other skin problems, haemorrhoids, perspiring feet, some eye problems, as a mouth wash etc[, ].
Many Acacia trees also yield greater or lesser quantities of a gum from the trunk and stems. This is sometimes taken internally in the treatment of diarrhoea and haemorrhoids[].

Agroforestry Uses:

The primary use of the species is for sand dune stabilisation[, ], and for low windbreaks in arid areas[].
Acacia ligulata is an excellent plant for revegetation work in arid lands and although it is not common in the Kalannie region it warrants investigation for use in revegetating areas of slight to moderate salinity. This species would be suitable for salinity and erosion control on colluvial earth soils and would be appropriate as a low windbreak[].

Other Uses

The wood is of very small dimensions and is not known to be utilized. It can be highly suitable for small-sized fuelwood[].

Propagation

Seed - best sown as soon as it is ripe in a sunny position in a warm greenhouse[].The dried seed of most, if not all, members of this genus has a hard seedcoat and may benefit from scarification before sowing to speed up germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. Sow the seed in Spring in a greenhouse. As soon as the seedlings are large enough to handle, prick them out into individual pots and grow them on in a sunny position in the greenhouse for their first winter. Plant them out in late spring or early summer, after the last expected frosts, and consider giving them some protection from the cold for their first winter outdoors.
Acacia seeds that have matured fully on the bush and have been properly dried have a hard seed coat and can be stored in closed containers without deterioration for 5 - 10 years or more in dry conditions at ambient temperatures. It is best to remove the aril, which attracts weevils and can lead to moulds forming. The arils are easilyremoved by placing the seeds in water and rubbing them between the hands, then drying the seeds and winnowing them[].