Prota 3: Dyes and tannins/Colorants et tanins
Bothalia 37(2): 173 (2007).
Rhus tomentosa L.(1753).
Wild currant, furry rhus, hairy taaibos (En). Sumac (Fr).
Origin and geographic distribution
Searsia tomentosa is found in eastern Zimbabwe and eastern and southern South Africa.
The wood, bark of roots and branches, and leaves of Searsia tomentosa are collected from the wild and used in tanning. The bark also produces fibre for rough rope. The wood is hard and tough, but it is only used as fuel because the trees are small. The fruits are edible, but of very poor flavour. Searsia tomentosa is an attractive shrub with potential as an ornamental and seed is available from specialist suppliers. It was one of the first Searsia species introduced into botanical gardens.
The leaves of Searsia tomentosa yield 8% tannin and the twigs 5.7%. The bark is rich in tannic acid.
Dioecious shrub or small tree up to 5 m tall, much-branched; bark smooth, grey-brown; branches shallowly ridged, densely red-hairy when young, older ones dark green. Leaves alternate, 3-foliolate; stipules absent; petiole up to 4 cm long; leaflets lanceolate-elliptical to obovate, 39 cm Χ 14 cm, terminal leaflet largest, base broadly tapering, margin entire or in upper part with 13 small teeth, leathery, yellowish to whitish hairy below. Inflorescence a lax, much-branched, axillary or terminal panicle, male one up to 9 cm long, female one up to 5 cm long. Flowers unisexual, regular, 5-merous; pedicel 12 mm long; calyx with ovate segments; petals c. 1 mm long; male flowers with 5 stamens; female flowers with superior, globose, 1-celled ovary, styles 3, stigmas headlike. Fruit a globose drupe 46 mm Χ 34 mm, densely grey-tomentose.
Searsia comprises approximately 110 species and occurs in southern Europe, Asia and Africa. Southern Africa is by far richest in species. Until recently, most authors did not separate Searsia from Rhus, although the separation has already been proposed at the beginning of the 1940s. Recent phylogenetic research using DNA and gene spacer data confirmed that Searsia is distinct from Rhus sensu stricto, which is limited to the Northern Hemisphere.
Other African Searsia species are used occasionally for dyeing: the bark of Searsia lancea (L.f.) F.A.Barkley gives a brown dye, that of Searsia pendulina (Jacq.) Moffett, more reddish-brown colours. The bark of Searsia undulata (Jacq.) T.S.Yi, A.J.Mill. & J.Wen is a traditional source of tannin in Namaqualand (South Africa) and the root of Searsia ciliata (Licht. ex Roem. & Schult.) A.J.Mill., the wood of Searsia lancea and the bark and wood of Searsia lucida (L.) F.A.Barkley have also been used for tanning. However, these species are more important for their edible fruits and/or timber.
Searsia tomentosa grows on rocky mountain slopes and on edges of low bushland vegetation, up to 2500 m altitude.
Genetic resources and breeding
Searsia tomentosa does not seem to be in danger of genetic erosion.
Most probably Searsia tomentosa will remain important for tanning only very locally. Possibly it will become more important as an ornamental.
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Correct citation of this article:
Jansen, P.C.M., 2005. Searsia tomentosa (L.) F.A.Barkley. In: Jansen, P.C.M. & Cardon, D. (Editors). Prota 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.