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Sophora tomentosa L. 1753
pronounced: SOFF-or-uh tow-men-TOW-suh
(Fabaceae – the pea family)
subfamily: Faboideae – the bean subfamily
common name: Silverbush
The Sophora genus consists of about 45 species of small trees and shrubs native to south-east Europe, southern Asia, Australasia, the Pacific islands, and western South America. Probably its most famous member is Sophora toramiro, which was formerly a common tree in the forests of Easter Island. The tree fell victim to the deforestation that wiped out the island’s forests by the 18th century, and later became extinct in the wild. The tree is being reintroduced to the island in a scientific project led jointly by Kew Gardens and the Götengorg Botanical Garden, where the only remaining plants of this species with a documented origin were propagated in the 1960s from seeds collected by Thor Heyerdahl.
Silverbush† is a shrub or small tree up to 5 m high, occurring in coastal areas in the Northern Territory, Queensland and northern NSW. It used to be common north from Port Stephens, but is now uncommon and found only north of Old Bar, near Taree. Populations previously recorded from Tweed Heads, Coffs Harbour and Iluka are now thought to be extinct. The largest known population in NSW, at Port Macquarie, is estimated at up to 500 plants; other populations are of fewer than 20 plants. It is listed there as an endangered species. Its habitat has been invaded by Bitou Bush, Chrysanthemoides monilifera ssp. rotundata, a native of southern Africa which was introduced into Australia for dune stabilization purposes, but which has itself become invasive.
Silverbush has also been affected by the clearing of dunal vegetation, inappropriate recreational use of beaches and foredunes, and damage to the plants during weed control programmes. It is not in quite as much danger in Queensland or the Northern Territory, although it has been affected by the development of coastal resorts. The plant whose seed pods are shown was on the foreshore of Geoffrey Bay, but was, alas, lost in Cyclone Yasi. I have not yet noticed any regeneration from residual seeds. In early 2015 another single plant appeared just above the high tide line on Picnic Bay beach, and this one is shown in most of the photographs. It has come into flower for the first time in November 2017. Another small colony of the plant has been observed recently on the Horseshoe Bay foreshore.
The leaves are 10–20 cm long, and there are generally 11–17 leaflets, ovate to more-or-less orbicular, 2–4 cm long, 1–3 cm wide, the apex obtuse or retuse, the margins entire, greyish to white tomentose; the petiole is 1–3 cm long, and the lateral petioles 2–4 mm long.
The inflorescence, which occurs in late winter, is a raceme 10–15 cm long, with pedicels 5–7 mm long; the calyx is about 6 mm long, and the corolla 2–2.5 cm long, pale yellow. The seed pod resembles a string of beads; it is indehiscent, 10–18 cm long, up to 14 mm in diameter, tomentose, strongly constricted between seeds; there are 5–10 seeds, each about 6 mm long. Their surface is smooth, and they are coloured olive, brown or black.
† This common name is rather misleading, as it is one of several different plants thus known
Photographs taken in Geoffrey Bay 2011, Picnic Bay 2015-2017
Page last updated 20th November 2017