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 heterophylla is a shrub or small to medium-sized tree with a spreading crown; usually growing up to 20 metres tall but exceptionally to 25 metres. The bole is often short and crooked, and can be up to 150cm in diameter[]. 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 tree is harvested from the wild for its valuable timber. It is occasionally cultivated as a timber crop and is also planted as an ornamental along roads[].

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

Africa - Madagascar, Réunion.

Habitat

Humid forests at elevations from 800 - 1,800 metres, occasionally to 2,500 metres[].

Properties

Medicinal Rating
Other Uses Rating
Habit	Tree
Height	15.00 m
Pollinators	Bees
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Acacia heterophylla is a plant of the moist tropics, growing in areas where the annual rainfall should be at least 1,500mm and divided evenly over the year[].

The growth rate of seedlings is usually high, in good conditions it can reach about 1 metre per year for the first 5 years after germination[]. It is estimated that trees need 100 years to reach a bole diameter of 70cm[].
In trials in Madagascar, the tree succeeded only at elevations of 900 metres with an annual rainfall of 1,700 mm[]. (Does this mean that the trees succeeded only above 900 metres or only below 900 metres?[].) Ten year-old trees had a diameter at breast height of 18cm and were 18 metres tall, but they had a bad shape[].
Rooting is superficial, which explains the often severe damage caused to the trees by cyclones[].
Natural germination occurs after disturbance of the forest, such as after a fire. Regeneration can be abundant under such circumstances[]. In Réunion, clear felling of the natural forest has been practised in order to establish pure, even-aged stands of this species as a result of natural regeneration[]. Regular weeding is necessary, twice a year for the first 3 years, to avoid smothering of the seedlings by weedy plants. Thinning is practised when the trees are 6 and 10 years old, to 1,250 stems/ha and 800 stems/ha, respectively. The eventual density to be reached after 50 years is 200 stems/ha[].
The yield of timber per tree in natural forest is often comparatively small due to the poor shape and short length of the bole; wood defects such as knots are common. Proper silvicultural practices may improve bole shape and length, and thus timber yield[].

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 is a natural pioneer species within its native range, rapidly establishing itself after disturbances such as fire or clear felling[]. It would make a useful species for reforestation projects[],

Other Uses

The heartwood is pinkish yellow to orange-brown; it is distinctly demarcated from the paler sapwood. The wood is easy to work; nailing and gluing properties are good, and the wood takes varnish well. It takes an excellent polish[]. A valuable wood, it is used for construction, local furniture, joinery, flooring, arts and handicrafts, and for the production of shingles[]. At one time it was used for the construction of small boats[].

Propagation

Seed - it 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. Germination takes place 1 - 3 weeks after sowing. Seedlings stay in the nursery for 6 - 8 months before being planted out[]. Direct sowing in the field is also possible[].
Seeds may remain viable for over 30 years[].

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