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 irroratum (Sieber ex Spreng.) Pedley
Common Name: Green Wattle
Acacia irrorata is an erect shrub or a tree with an open crown; it usually grows from 5 - 12 metres tall, but can reach 20 metres on favoured sites. The bole is moderately straight and cylindrical and can be around 50 - 70% of the total tree height[
]. Unlike most of the Australian Acacias, this species retains its true leaves into maturity and does not develop phyllodes.
The plant is a good producer of tannins. It has potential for use as a fuel crop and is often grown as an ornamental.
The plant's ability to regenerate rapidly makes it a potential weed species[
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 - Victoria, New South Wales, southeastern Queensland
Rainforest margins, open forest, scrub-forest, in valleys or on hillsides, often in sandy or volcanic soils[
|Other Uses Rating||
|Cultivation Status||Ornamental, Wild
Acacia irrorata is a plant of the warm temperate to subtropical regions of eastern Australia, where it is found at elevations up to 1,300 metres. It grows best in areas where annual daytime temperatures are within the range 18 - 32°c, but can tolerate 10 - 39°c[
]. When dormant, the plant can survive temperatures down to about -10°c, but young growth is more tender and can be severely damaged at -1°c[
]. It prefers a mean annual rainfall in the range 750 - 1,000mm, but tolerates 600 - 1,100mm[
Requires a sunny position in a well-drained soil[
]. Prefers a soil on the heavy side, but tolerates a range of well-drained soils of medium to low fertility[
]. Prefers a pH in the range 5.5 - 6.5, tolerating 5 - 7[
A fast-growing species that regenerates rapidly after fire[
The soft green foliage of this tree is a feature that makes it an attractive ornamental[
Plants can flower at any time of the year[
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.
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 tree can be utilized for shade, shelter, soil conservation on steep slopes, and as an ornamental[
The bark is a very good source of tannins[
]. The bark of subsp. irrorata is thin and the tannin content inferior to that of Acacia mearnsii[
]. 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 pale brown. The wood is hard, moderately and dense, but probably not as durable as many other Acacias. It can be used for posts and poles[
The wood is a good fuel when dry[
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[