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: Blue-Leaved Wattle

General Information

Acacia saligna is a small, prickly, fast-growing, often multi-stemmed evergreen shrub or tree growing up to 9 metres tall, though often smaller[, , ]. Plants can be single-stemmed or multi-stemmed, with mature trunks 20 - 40cm in diameter. Plants produce suckers and sometimes form thickets[]. Although it produces leaves as a seedling, llike most members of the genus the mature plant does not have true leaves but has leaf-like flattened stems called phyllodes[].
The plant is an important source of tannins, especially in southwestern Australia[]. It is harvested from the wild for local use as a food. It is extensively from the wild, and sometimes also cultivated in semi-arid areas of north Africa and the Middle East, as windbreaks, for coastal sand dune fixation and for fuel[]. It has been suggested as a potential commercial seed crop for areas such as Western Australia[]. There is a weeping form that produces an abundance of attractive yellow flowers and is often grown as an ornamental in the tropics and subtropics[, ].
Because of its hardiness and profuse reproductive abilities, this tree has become a serious menace in parts of South Africa by invading native ecosystems and displacing indigenous vegetation. It spreads both by root suckers and seed[], infests water courses (sometimes decreasing the water available for irrigation), and has proved difficult to eradicate[].

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

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Range

Australia - native in Western Australia - naturalized in Queensland, New South Wales, Victoria, Tasmania, South Australia.

Habitat

A variety of habitats including poor sandy soils; clays; sand plains (usually near creeks and rivers); deep sands near watercourses; the base of granite boulders; coastal dune systems (often forming dense thickets in the hollows between sand hills)[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	5.00 m
Growth Rate	Fast
Pollinators	Insects
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Succeeds throughout the lowland tropical, subtropical and warm temperate regions of the world, where it is found naturally at elevations up to 300 metres[]. In its native habitat, the summer temperature ranges from about 23 - 36°c, winter temperatures from 4 - 9°c. The plant does not withstand frost and grows best where the winter and summer means are between 13° and 30°c respectively[]. Plants can tolerate occasional frosts down to about -5°c[]. Particularly drought hardy, it grows where annual rainfall is as low as 250 mm, though it probably does better with 350 - 600 mm, and thrives where annual rainfall is as high as 1,000 mm[].
Succeeds in full sun and in light shade[]. Grows mainly on sandy, coastal plains, but is found from swampy sites and riverbanks to small, rocky hills (often granitic) and coastal slopes[]. It occurs on poor acid or calcareous sands, under the most dry and adverse soil conditions, in moderately heavy clays and a range of podzols[]. Plants are adaptable to barren slopes, derelict land, and exceptionally arid conditions[]. They are also said to be tolerant of saline soils, salt spray, shade and occasional waterlogging[]. Established plants are very drought tolerant[, ].
A fast-growing but relatively short-lived plant, it can often reach up to 8 metres tall with a spread as great as its height in just 4 or 5 years[]. In very dry situations, growth rate is slower[]. The plant generally lives for 10 - 20 years in cultivation[].
Trees coppice freely and also produce suckers[, , ], and production for browse and wood can begin just 3 years after planting out, with yields gradually building to 6 years[].
Coppice rotations for fuel of from 5 - 10 years have all been tried with this species[].
Annual yields of fuel wood vary from 1.5 to 10 cubic metres per hectare, depending on site[].
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[].
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 8 - 12cm long, 4 - 6mm wide, with dark brown to black, oblong to slightly elliptic seeds 5 - 6mm long[, ].

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

Flowers - cooked[]. Rich in pollen, they are often used in fritters.

The damaged bark exudes copious amounts of a very acidic gum that seems to show promise for use in pickles and other acidic foodstuffs[].

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[].

Agroforestry Uses:

An extremely rugged tree, adaptable to barren slopes, derelict land, and exceptionally arid conditions[]. It grows rapidly and is used for reclaiming eroded hillsides and wastelands and for stabilizing drift sands[]. It has been used in the rehabilitation of sand mining areas[]. This is one of the best woody species for binding moving sand, including in coastal regions[, ]. It is useful for windbreaks, amenity plantings, beautification projects, and roadside stabilization in semiarid regions[, ].
Plants respond well to cutting and can be grown as a hedge[]. Their thorns make them an effective security hedge[].

Other Uses

A yellow dye is obtained from the flowers[]. It can dye wool a lemon-yellow colour by using an alum mordant[].
A green dye is obtained from the seed pods[].

A gum is obtained from the trunk and branches. It is similar to gum arabic (Vachellia nilotica)[]. The damaged bark exudes copious amounts of very acidic gum. Such acid-stable gum has promise for use in pickles and other acidic
foodstuffs[].

The bark is a source of tannins[, ]. Tannin content can range from 19 - 30% in different regions[]. Bark harvested for its tannins should only be taken from mature stems, and only when the sap is rising at the beginning of the growing season - which is when the tannin content is highest and the bark is most easily removed from the wood[].

The wood is prettily grained and, if larger, it would be suitable for cabinet-work[]. It has been successfully processed into particle board[]. The stems are used for vine stakes and small agricultural implements[].
The wood is used for fuel and also to make charcoal[, ]. The wood is sometimes reported as sappy, light and not popular for firewood[].

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[].
Cuttings of half-ripe wood with a heel, mid summer in individual pots in a frame[]. Overwinter in a greenhouse for the first winter and plant out in their permanent positions in late spring or early summer. Fair percentage[].