Acacia mucronata

Willd. ex H. L. Wendl.

Narrow-leaved wattle

Fabaceae Edible: Seeds 1,485 iNaturalist observations

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Summary

Acacia mucronata, the variable sallow wattle or narrow-leaved wattle, is a shrub or small tree to 5 m high. It is native to southeast Australia, mainly the states of Tasmania and Victoria (where it is widespread and common in forests and woodland, mostly south of the Great Dividing Range). It often grows as an understorey tree or shrub in eucalypt forest or as a dominant in scrubland. In drier regions of its distribution, like in northeast Tasmania, it often grows along creeks and sheltered coastlines.

Description

A shrub or small tree. It grows 5 m tall. There are prickles along the stem. The leaves are twice divided and there are 8-18 pairs of pinnae. There are up to 50 pairs of pinnules on each pinnae. The flowers are yellow. They are in large clusters at the ends of branches. The pods are flattened.

Edible Uses

The following uses are based on the closely related A. longifolia and almost certainly apply to this species as well. Flowers are cooked and, being rich in pollen, are frequently used in fritters. Seeds are roasted and are starchy; acacia seeds are highly nutritious, containing approximately 26% protein, 26% available carbohydrate, 32% fibre, and 9% fat. The fat content is higher than most legumes, with the aril supplying the bulk of fatty acids, which are largely unsaturated — a health advantage, though one that presents storage challenges since such fats oxidise readily. The mean total carbohydrate content of 55.8 ± 13.7% is lower than lentils but higher than soybeans, while the mean fibre content of 32.3 ± 14.3% exceeds other legumes such as lentils, which register 11.7%. Energy content averages 1480 ± 270 kJ per 100g. Wattle seeds are low glycaemic index foods — their starch is digested and absorbed slowly, producing a small but sustained rise in blood glucose and delaying the onset of exhaustion during prolonged exercise. Seedpods, which grow up to 10cm long, can also be roasted.

Medicinal Uses

None known.

Distribution

It is a temperate plant. Arboretum Tasmania.

Where It Grows

Australia, Tasmania,

Cultivation

Prefers a sandy loam and a very sunny position. Succeeds in any good garden soil that is not excessively limey. This species is fairly lime-tolerant. Plants are very tolerant of drought, they succeed in a hot dry position and in poor soils. A fairly wind resistant tree, growing well in maritime areas. Tolerates some salt in the soil. Hardy to about -10°c for short periods, it can be grown outdoors in many of the milder areas of the country though, even in Cornwall, it is liable to be cut back to the ground in excessively cold winters. It can resprout from the base. This species is closely related to A. longifolia, but is considered to be hardier and is possibly the hardiest of all the Acacias in Britain. Dislikes root disturbance. A very ornamental plant. 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.

Propagation

Seed is best sown as soon as it is ripe in a sunny position in a warm greenhouse. Stored seed should be scarified, pre-soaked for 12 hours in warm water, then sown in a warm greenhouse in March; germination takes 3–4 weeks at 25°C. Once seedlings are large enough to handle, prick them out into individual pots and grow on in a sunny greenhouse position through their first winter. Plant out in late spring or early summer after the last expected frosts, with some cold protection recommended for the first winter outdoors. Cuttings of half-ripe wood with a heel can be taken in July or August, potted individually in a frame, overwintered in a greenhouse, and planted out in late spring or early summer the following year. Success rate is fair.

Other Uses

The following uses are based on the closely related A. longifolia and almost certainly apply to this species. A yellow dye is obtained from the flowers and a green dye from the seed pods. The plant's extensive root system helps prevent soil erosion and is used to stabilise sandy soils and steep banks. Trees are planted as screens in Australia, and this species is often grown as a rootstock for grafting lime-intolerant members of the genus. The wood is pale and tough. This plant is a nitrogen fixer.