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[
Racosperma macdonnellense (Maconochie) Pedley
Acacia macdonnellensis is a shrub or a tree with one to several trunks and a spreading crown; it can grow 3 - 6 metres tall[
]. 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 as a food, and has the potential to become a cultivated crop in arid areas
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.
Australia - southern Northern Territory, eastern Western Australia
Found mainly in skeletal soils, in rocky mountain ranges, usually towards the tops of ridges; at elevations from 550 - 1,150 metres[
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Acacia macdonnellensis is a plant of arid regions in the subtropical and tropical zones of central Australia, where it is found at elevations up to 1,150 metres. It grows best in areas where annual daytime temperatures are within the range 24 - 33°c, but can tolerate 8 - 42°c[
]. Frosts can occur in much of the plant's range, it is able to survive temperatures down to about -5°c, but young growth is more tender and can be severely damaged at -1°c[
]. It prefers a mean annual rainfall in the range 200 - 250mm, but tolerates 150 - 300mm, and can withstand a dry season of 8 - 12 months[
Requires a sunny position. Requires a well-drained soil, preferring a light to medium texture and succeeding where the fertility is very low[
]. Prefers a pH in the range 5 - 6.5, tolerating 4.5 - 7[
]. Established plants are very drought tolerant.
A slow-growing but long-lived species.
Plants respond poorly 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[
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[
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 30 - 95mm long and 2 - 4mm wide, containing dark brown seeds 2.5 - 5mm 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 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[
The plant can be used to form low windbreaks.
The wood makes a good quality fuel.
Seed - best sown as soon as it is ripe in a sunny position[
]. Stored seed should be scarified, pre-soaked for 12 hours in warm water and then sown. The seed germinates in 3 - 4 weeks at 25°c[
]. As soon as the seedlings are large enough to handle, prick them out into individual pots and grow them on in a sunny position until large enough to plant out.
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 of half-ripe wood with a heel, in individual pots[
]. Fair percentage[