Acacia redolens Seeds | Prostrate Acacia, Bank Wattle
LATIN NAME: Acacia redolens
COMMON NAME: Prostrate Acacia, Bank Wattle
Plant Profile
Acacia redolens is a prostrate wattle from southern Western Australia, grown as a ground cover for slopes and road edges. It grows on the south coast between Albany and Esperance, on sand and gravel over limestone, in scrub that is baked in summer and windswept all year. The plant spreads three to six metres across but rarely rises more than a metre, with grey-green, broadly oval phyllodes that are thick, leathery and strongly scented when crushed. In late winter and spring it covers itself with small, bright yellow flower heads, followed by narrow, curled pods. The seed is hard-coated and persists in the soil for years. It is one of the most widely planted ground-cover wattles in California and Australia, where its tolerance of drought, wind and poor soil makes it useful on embankments and in car parks. A low form sold as ‘Low Boy’ is the usual clone in the trade.
Science & Biotechnology
Acacia redolens is a phyllodinous wattle: what look like leaves are flattened leaf stalks, and the true leaves are reduced to small scales on the seedling. The phyllodes are held more or less vertically, which reduces the leaf area exposed to the midday sun and is one of the reasons the plant survives on hot, exposed sites. The species is diploid and belongs to the Australian acacia group that dominates the southern arid zone, and it fixes nitrogen through root nodules in partnership with soil bacteria. Its seed carries a small oily appendage that attracts ants, which carry it into their nests and bury it, giving the seed both dispersal and a safe site. The plant is short-lived by tree standards, often declining after fifteen years, and it regenerates from seed rather than from suckers. Provenance matters: coastal forms are prostrate, while inland forms can be taller and less hardy.
Uses & Benefits
Its main use is as a ground cover on slopes, embankments, road verges and large commercial landscapes, where it knits the surface together within two seasons and needs no irrigation after the first year. It is also planted for erosion control on sandy and gravelly soils and as a pioneer in revegetation, since its nitrogen fixation improves the ground for later species. The flowers are a useful source of pollen for bees in late winter, and the seed is eaten by parrots. The wood is small and is used for fuel, and the bark has some tannin. In a garden it works as a weed-suppressing mat on a dry bank, but it is too wide for a small bed and it will swallow low plants. It is not a lawn substitute: it does not take foot traffic, and it becomes leggy and bare in the centre after a decade.
Growing from Seed
Break the hard seed coat with a file or with hot water, then soak overnight and sow one centimetre deep in a sandy mix at 20 to 25 degrees; germination is quick and usually high. The seedling develops a strong taproot, so sow in a deep tube and plant out young. Choose a site in full sun with sharp drainage and plenty of room; the plant spreads several metres and does not transplant well once established. Water through the first summer, then leave it alone. It tolerates frost to about minus seven, coastal wind and alkaline soil, but not shade or waterlogging. Prune lightly after flowering to keep it dense, and cut back hard if it becomes leggy; it resprouts from old wood. The plant is short-lived, so let some seed set to replace it.
Our Take
A flat, wide wattle for a hot bank, with scented leaves and yellow winter flowers. Plant it where it can spread and forget it.
Related Reading
If Prostrate Acacia appeals to you, these related plants are worth a look: