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 leptocarpa is a tree that usually grows up to 15 metres tall, though sometimes it is only a shrub, growing up to 4 metres from a single very short stem. In larger plants the boles can be unbranched for up to 4 metres and 25cm in diameter[, ]. 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 tree is harvested from the wild for local use as a source of wood. It can be used as a pioneer in restoring native woodlands and establishing woodland gardens. A well-shaped tree with beautiful flowers, casting a useful moderate shade, it could be useful in amenity areas[].

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

Australasia - Western Australia, Northern Territory, Queensland to southern New Guinea.

Habitat

Open eucalypt and/or Melaleuca forests, low open forest and low open woodland on the flats and gentle slopes of the coastal lowlands, including stabilized dunes, extending to the slopes and ridges further inland[, ].

Properties

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

Cultivation Details

Acacia leptocarpa is a plant of coastal and sub-coastal belts, preferring hot humid to sub-humid climatic zones in the tropics and subtropics, where it can be found at elevations up to 550 metres[]. It grows best in areas where annual daytime temperatures are within the range 22 - 33°c, but can tolerate 10 - 39°c[]. It prefers a mean annual rainfall in the range 750 - 1,500mm, but tolerates 500 - 1,750mm[].
Requires a position in full sun or bright light[]. Grows in the wild on sandy or rocky soils, sometimes on laterite[]. It can also succeed on heavy clays and soils of low fertility[, ]. It has been planted successfully on salt-affected land in Thailand, where there was a dry season of 6 - 8 months[]. Succeeds on well-drained or waterlogged soils[]. Prefers a pH in the range 4.5 - 6, tolerating 4 - 6.5[].
A fast-growing plant, especially when young - plants can commence flowering when only 14 months old from seed[].
This species hybridizes with Acacia auriculiformis and Acacia creata in its natural range in Australia[].
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:

The tree can fix atmospheric nitrogen and so can grow well on infertile soil. The high biomass it produces indicates great potential for use in improved fallows and other agroforestry systems[]. It is used in mine-site rehabilitation projects in northern Australia[].
It casts a useful, moderate shade, and can be advantageously planted in association with other crops[].
The plant is a natural pioneer species and can be used in reforestation projects and also in establishing woodland gardens[].

Other Uses

The bark contains around 10% tannins[]. 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 heartwood is dark brown; it is clearly demarcated from the white sapwood, The decorative wood is close grained and hard. Not often available in larger sizes, it is useful in turnery and cabinet work and can provide small posts and
poles for village use[, , ].
The wood is suitable for fuel and for making charcoal[]. Wood from 4-year-old trees burnt fast and gave a charcoal of high heating efficiency[].

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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