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 microbotrya is a bushy shrub or a tree that can grow 2 - 7 metres tall[]. Sometimes a single stem up to 100cm long before branching and up to 11cm in diameter is produced, at other times the plant can branch into 2 - 4 main trunks from the base[]. The plant often suckers and can form dense thickets[]. Although it produces true leaves as a seedling, 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 food and source of materials. It has been suggested as a potential commercial seed crop for areas such as Western Australia[].

Known Hazards

The seed of many Acacia species, including this one, 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 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 - southwestern Western Australia

Habitat

Found in a variety of habitats but often on clay loam or sandy loam flats, often near watercourses, in Eucalyptus woodland[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Tree
Height	5.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Acacia microbotrya is native to the Mediterranean climate of southwestern Western Australia, where it can be found at elevations up to 430 metres. It grows best in areas where the mean maximum temperature of the hottest months can reach 27 - 34°c, and the mean minimum in the coldest month can fall to 4 - 8°c. The plant can experience moderate frosts, down to around -5°c for short periods. Mean annual rainfall can vary from 320 - 625mm, with a variable dry season that can range from 7 - 8 months[].
Requires a sunny position. Grows best in a well-drained, light to medium-textured soil[]. Plants can tolerate low to moderate salinity[]. Prefers an acid to neutral soil[]. Established plants are tolerant of drought[].
A widespread, variable species which, together with 43 relatives Australia-wide, constitutes the informal ‘Acacia microbotrya group’. Some members of the group, particularly Acacia chrysella , Acacia brumalis , Acacia chamaeleon and Acacia microbotrya from Western Australia, are extremely variable and further studies are needed to elucidate the complex variation patterns and clarify the relationships between these species. It is likely that future work will result in the recognition of additional species within this species-complex[].
A fast-gowing species[]. It suckers freely and probably also responds well to coppicing[].
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[].
Acacia microbotrya is especially closely related to Acacia amblyophylla and Acacia jennerae and superficially similar to Acacia galeata[].
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

Seed - cooked[, ]. It can be eaten in the same ways as other small legume seeds and is also ground into a powder then used as a flavouring in desserts or as a nutritious supplement to pastries and breads[]. The seedpods are up to 15cm long, occasionally reaching 20c, and around 6 - 8mm wide, with black, oblong to elliptic seeds 5.5 - 8mm long[]
Acacia seeds are highly nutritious and contain around 26% protein, 26% available carbohydrate, 32% fibre and 9% fat. The fat content is higher than most legumes with the aril providing the bulk of fatty acids present. These fatty acids are largely unsaturated. The energy content is high in all species tested, averaging 1480 ±270 kJ per 100g. The seeds are low glycaemic index foods - the starch is digested and absorbed very slowly, producing a small, but sustained rise in blood glucose and so delaying the onset of exhaustion in prolonged exercise[].

The ground seed can be used to produce a high quality, caffeine-free coffee-like beverage[].

The plant probably produces an edible gum by exudation from the trunk and stems[]. A pleasant, sweetish taste[]. A tree can often produce 20 kilos of gum in one season - the native Australians would often store it in hollow trees for winter use[].

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[].

Other Uses

The bark is a source of 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[].

A good quality gum is produced in abundance. It forms a superior gum arabic (see Vachellia nilotica)[].

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[].