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 polystachya is an evergreen, multi-stemmed, bushy shrub 3 - 4 metres tall when growing in exposed positions near the coast, becoming a tree that can grow up to 25 meres tall in sheltered positions inland[, ]. 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 of its wood. It has good potential for use in agroforestry systems, especially in exposed positions near the coast.

Known Hazards

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 - northeastern Queensland

Habitat

Alluvial soils often near watercourses in semideciduous mesophyll vine thicket and deciduous vine thicket or along beaches by the coast; at elevations up to 500 metres[].

Properties

Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Acacia polystachya is a plant of the moist tropical zone of northeastern Australia, where it is found at elevations up to 500 metres. It grows best in areas where annual daytime temperatures are within the range 24 - 32°c, but can tolerate 15 - 38°c[]. The plant does not experience frost in its native range. It prefers a mean annual rainfall in the range 1,200 - 2,000mm, but tolerates 1,000 - 2,200mm[].
Requires a sunny position. Prefers a light, well-drained soil that can be rather dry and of low fertility[]. Prefers a pH in the range 5 - 6, tolerating 4.5 - 6.5[]. Plants succeed in calcareous soils[]. Plants are tolerant of salt-laden winds and saline soils[].
A fast-growing plant, it can commence flowering when around 3 years old[, ].
The plant will coppice successfully, but only if cut well above the ground. Three-year-old trees coppiced poorly near ground level but 92% of stumps coppiced at 30 m and 73% at 50 cm responded vigorously[].
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

None known

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:

It can be planted in calcareous soils near the coast in order to provide shelter and protection from salt-laden winds[].
Iy has good potential as an agroforestry plant, succeeding in soils of low fertility, providing high biomass, fixing atmospheric nitrogen and providing light shade[].

Other Uses

The heartwood is dark brown or red with attractive markings. The wood is hard and heavy[]. It is used traditionally for making spears, but is not otherwise utilizes[].
The wood is a good fuel and makes a good charcoal[].

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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