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:

General Information

Acacia pruinocarpa is a shrub or a tree with a dense and spreading crown; it usually grows from 3 - 8 metres tall, reaching 12 metres on favourable sites. The bole of taller trees can be up to 6 metres tall and 25cm in diameter[, ]. 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 tree is harvested from the wild for local use as a food and source of materials. It has potential as a food crop in arid regions and is often grown as an ornamental.

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 - Western Australia, northwestern South Australia, Northern Territory.

Habitat

Arid areas, growing in a variety of topographic situations, usually in sand or loam, often with Acacia aneura and spinifex[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Tree
Height	6.00 m
Growth Rate	Slow
Pollinators	Insects
Cultivation Status	Ornamental, Wild

Cultivation Details

Acacia pruinocarpa is a plant of arid regions in the subtropical and lower tropical zones of central Australia, where it is found at elevations up to 750 metres. It grows best in areas where annual daytime temperatures are within the range 22 - 35°c, but can tolerate 8 - 43°c[]. When dormant, the plant can survive temperatures down to about -5°c, but young growth is more tender can be severely damaged at -1°c[]. It prefers a mean annual rainfall in the range 200 - 250mm, but tolerates 125 - 300mm[].
Requires a sunny position[]. Requires a well-drained soil, preferring soils of light to medium texture and succeeding in soils of low fertility[]. Prefers a pH in the range 6 - 7, tolerating 4.5 - 8[]. Established plants are very drought tolerant[].
An attractive ornamental plant and shade tree[].
A slow-growing species[].
The plant responds well to coppicing and also survives fire by resprouting from the base and producing root suckers[].
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[].

Edible Uses

Seed - cooked[]. It can be eaten in the same ways as other small legume seeds and is also ground into a powder then used as a flavouring in desserts or as a nutritious supplement to pastries and breads[]. The seedpods are up to 70mm long and 8 - 13mm wide, with dark red-brown, oblong-elliptic seeds 4 - 7mm 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[].

The above report cited Acacia notabilis as a synonym of Acacia pruinocarpa. The two are not synonymous, and it is possible that the reports of edibility for this species more properly rest with Acacia notabilis[].

A sweet gum exudes from the trunk and branches[]. It is not produced in large quantities[].

Medicinal

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[].

Other Uses

The wood is close-grained, tough, strong, durable ; it splits freely, and is probably useful for turnery, etc[].
The above report is for Acacia notabilis, which is described as a tree that can grow up to 9 metres tall. However, the Flora of Australia[].actually describes Acacia notabilis as a shrub growingup to 3 metres tall. The Flora of Australia also mentions that Acacia pruinocarpa (a tree that does fit the description in []) has at times been wrongly described as Acacia notabilis[, ]. It is quite likely that the description of the wood given here more properly belongs to Acacia pruinocarpa[].
The following report is for Acacia pruinocarpa:-
The wood is an attractive dark ebony colour, has a high density and as such has potential for use in furniture manufacture, as a craft wood and also for making musical instruments. However, it is very susceptible to attack by borers and quickly rots once such damage occurs[].

The wood is used for fuel[].

Propagation

The 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.
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[].

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