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 holosericea is a shrub or a usually multi-stemmed tree with a large, dense crown; it can grow 3 - 8 metres tall[, ]. 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 a traditional food and medicine, though little used by modern society. It is also grown as a windbreak, soil stabilizer and in land restoration projects. It is sometimes grown as an ornamental, valued for its silver foliage, long, yellow flower spikes and twisted seedpods[, ].

Known Hazards

The plant (probably the seeds[]) has been used as a fish poison[].
The seed of many Acacia species 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, including this species, 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, Northern Territory, Queensland.

Habitat

Gravelly sand or loam, commonly forming communities along watercourses[]. Usually grows in open forest but sometimes found in monsoon forest and vine thickets, at elevations up to 900 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Shrub
Height	6.00 m
Growth Rate	Fast
Pollinators	Insects, Birds
Cultivation Status	Ornamental, Wild

Cultivation Details

Acacia holosericea is a plant of the drier, seasonal tropics of northern Australia, where it is found at elevations up to 750 metres. It grows best in areas where annual daytime temperatures are within the range 24 - 32°c, but can tolerate 12 - 45°c[]. When dormant, the plant can survive temperatures down to about -1°c[]. It prefers a mean annual rainfall in the range 600 - 1,200mm, but tolerates 250 - 1,600mm[].
Requires a sunny position[]. Dislikes heavier soils[]. Succeeds in soils of low fertility[]. Prefers a well-drained soil, but tolerant of dry conditions and seasonal inundation of the soil[]. Prefers a pH in the range 5.5 - 7.5, tolerating 4.5 - 8.5[].
The early and abundant seeding of this plant has the potential of making it a weed. Seed dispersal is prompted by propulsion from drying dehiscent pods. Browsing vertebrates sometimes also play a role in seed dispersal[].
Early rapid growth makes this tree a highly productive fuelwood source. Trees 4 years old can yield up to 13 tonnes per hectare[].
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[].
The tree can be lopped or pollarded, but generally does not respond well to coppicing[].
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

Seeds - cooked[]. Although edible, the seeds contain toxic substances and need to be carefully prepared in order to destroy these substances[]. They are traditionally made into a flour[]. The seeds have an unpleasant odour whilst being prepared[]. The pods are 20 - 80mm long and 2 - 3mm wide, containing rectangular black seeds 2.5 - 3.5mm long and up to 2mm wide[].

Medicinal

The phyllodes, bark and pods are used traditionally for the treatment of pruritic skin conditions, headache and tropical infection[].

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:

Due to its large dense crown, this species is used to form the lower part of a multistorey windbreak in conjunction with Eucalyptus camaldulensis[].
The plant grows fast, has a dense crown, succeeds on infertile soils, fixes atmospheric nitrogen and has vigorous colonizing characteristics. It is a natural pioneer species, rapidly invading disturbed areas, and can be used for restoring native woodland or establishing woodland gardens[]. It is also an ideal plant to use for the revegetation and restoration of degraded mining sites as well as for the fixation of sand dunes[].

Other Uses

The plant was used to make a soap[]. No more details are given[].

The heartwood is dark brown. The wood is hard with a high density, and can be turned into small decorative articles[, ]. Traditionally, it was used to make spear shafts[].
The wood is an excellent fuel that can readily be converted to charcoal[, ]. The calorific value of the wood is estimated at 4,670 kcal/kg and the charcoal 7,536 kcal/kg[].

Propagation

Seed - it has a hard seedcoat and benefits from scarification before sowing in order to speed up and improve 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.
Seeds can store for 14 years at room temperature with only 11% loss of viability[].

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