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: Hickory Wattle

General Information

Acacia implexa is an evergreen tree that can grow from 3 - 12 metres tall, reaching 15 metres on selected sites. The trunk sometimes divides into two either near the ground or at about 2 metres; each bole can be 15 - 40cm in diameter, exceptionally to 60cm. The plant often suckers and can form clumps of growth[, , ]. Although it produces true leaves as a seedling, and also as a yound plant, llike 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 as a medicine and source of materials. It has potential as a crop for high volume wood production, and can be used in soil stabilization programmes.
Introduced into South Africa as a plantation crop, the tree has escaped from cultivation and it has been declared a weed there[].

Known Hazards

Stock deaths have been caused by ingestion of green pods[].
The bark contains high levels of tannins and saponins and was traditionally used as a fish poisin to stun fish so that they could be captured for eating[].
Although poisonous, saponins also have a range of medicinal applications and many saponin-rich plants are used in herbalism (particularly as emetics, expectorants and febrifuges) or as sources of raw materials for the pharmaceutical industry. Saponins are also found in a number of common foods, such as many beans.
Saponins have a quite bitter flavour and are in general poorly absorbed by the human body, so most pass through without harm. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of raw foods that contain saponins.
Saponins are much more toxic to many cold-blooded creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish and make them easy to catch[].
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 - Victoria, New South wales, Queensland

Habitat

Found in a variety of situations but often in shallow, well-drained soil in hilly country in woodlands or open forest[].

Properties

Weed Potential	Yes
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

Acacia implexa is a plant of the temperate to subtropical zones of eastern Australia, mainly in higher rainfall areas. It is fairly frost-tolerant when dormant, surviving short periods with temperatures falling to around -6°c[]. The plant grows best in moister regions, cropping well in an area where the mean annual rainfall was 825, (where it attained a height of 3.1 metres and a dbh of 38mm at 2.6 years, increasing to 4.2 metres with a dbh of 44mm at 5.2 years[].
Requires a sunny position. Established plants are reasonably drought tolerant[]. Requires a well-drained soil, succeeding in a variety of textures even when the fertility is low[]. Plants are tolerant of strong winds, though they are apt to become wind-shaped[].
A vigorous, long-lived, fast to moderately fast growing species[].
The plant responds well to coppicing, and can also sucker freely, particularly if the main stems are cut back severely or if the roots are disturbed[].
The plant is resistant to debarking by stock[].
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[].
This species is often confused with Acacia melanoxylon[].

Edible Uses

None known

Medicinal

The bitter bark of this tree probably possesses medicinal properties[]. A lotion made from the bark is ued to treat sores and skin disorders[, ].
The bark of young trees contains a very pleasant bitter[].
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 more or less of a gum from the trunk and stems. This is sometimes taken internally in the treatment of diarrhoea and haemorrhoids[].

Agroforestry Uses:

The plant has a spreading root system and is an excellent plant to use for erosion control on rocky hills[].
Moderately useful for shelter purposes, the tree is occasionally planted in windbreaks and for shade on slopes and tablelands[].

Other Uses

The bark contains much tannin. One analysis showed 7.82% of tannic acid and 20.54% of extract, whilst another showed 14.16% of tannic acid and 33.51% of extract[].

The leaves produce a yellow dye with alum, and brown dye when copper is used as mordant[].

The heartwood is dark-brown with paler stripes; the sapwood is paler in colour. The wood is close-grained, strong and hard. Of good quality, it has been used for turning, furniture making, parquetry etc[, , ].
The wood is used for fuel[].

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[].