Searsia erosa

(Thunb.) Moffett, comb. nov.

Family: Anacardiaceae (mango family)
Common names: Broom karee, Besembos

Searsia erosa tree

The Free State is a haven for many different plant species, one of the most interesting inthe family Anacardiaceae being Searsia erosa and it grows well in the garden. Its large, soft, yellow green shape stands out in the landscape. Many Searsia species, either shrubs or trees, are popular garden plants. Their gene pool is large because hybridization (cross pollination) takes place easily.

Description
Searsia erosa leavesThis much-branched, evergreen shrub or small tree grows to about 4 m. in height, but spreads to about 9 m across. It is fairly fast growing and has brown bark. The trifoliate leaves are very distinctive. The leaflets are very long (up to 130 mm) and narrow (3 mm wide). They usually have toothed, jagged margins which look as if they have been gnawed, giving rise to the specific name. Leaves are attached to the stem by a petiole which is up to 30 mm long, but the leaflets are sessile. The leaflets appear leathery, hairless and sticky in texture, and olive-green or yellowish green in colour, with paler undersides. The midribs are prominent and crushed leaves often emit a strong turpentine or resinous odour.

Small, white or greenish yellow flowers, are borne in loose, slender sprays and appear in early summer from October to December. They are followed by yellowish, sometimes light brown, hairless and shiny fruits (drupes) from January to April.

Searsia erosa is not threatened nor endangered.

Distribution
It occurs in karroid areas of the Cape provinces, Free State and Lesotho, usually in large numbers on rocky koppies (hills).

Derivation of name and historical aspects
Searsia was named after Paul B. Sears (1891-1990) who was head of the Yale School of Botany, and erosa (Latin) refers to the leaf margins which are toothed or look gnawed.

Most of the species grown in southern Africa, belonging to the genus Rhus, have been placed in Searsia. There are about 111 species in southern Africa. Searsia are deciduous or evergreen shrubs and trees, armed or unarmed suffrutices, shrub or trees, and stems and branches have prominent lenticels. Leaves of this genus are compound with 3 leaflets (trifoliolate).

Ecology
Bees and other insects pollinate the flowers. Birds eat the ripe fruits. Searsia erosa can withstand harsh environmental conditions such as drought and frost.

Uses and cultural aspects
This plant is not grazed, but is good for conserving soil and preventing erosion. Branches as well as leaves can be used for thatching and making brooms, hence its common name. The plant is a good garden subject in harsh environments and is sometimes used for hedges. It is said to feature in rainmaking ceremonies in Lesotho (Palgrave 1981) and various parts are used to treat diarrhoea in both man and cattle.

Growing Searsia erosa

Searsia erosa has delicate, airy foliage. It can be grown in the garden as a soft, screening plant or hedge and it is attractive enough to use as a focal point in gardens where it grows well. It can be replaced in the garden by S. tenuinervis, in areas where the latter grows.

Searsia erosa survives extremes of temperature and thrives in gardens where temperatures soar to 42 C in summer and plunge to -10 C in winter. It grows well on stony and gravel soil as these are well drained. Avoid waterlogged soils with poor drainage.

This species grows easily from seed, if fresh, unparasitized seed can be found. Before planting the seed, place it in water. Discard all seeds that float to the surface, as they will not germinate. Rub off all fleshy bits from the remaining seed and dry the seeds in a sunny place. Then plant them in a mixture of gravel, loam and river sand. Only lightly cover the seeds and keep them moist, but never too damp. Seeds should start germinating about 8 weeks after sowing. Prick them out into individual bags when they have 4 leaves. Once plants are 0.5 m high they are ready to be planted out in the garden.

References

  • MOFFETT, R.O. 2007. Name changes in the Old World Rhus and recognition of Searsia (Anacardiaceae). Bothalia 37(2):165-175
  • ACOCKS, J.P.H. 1988. Veld types of South Africa, edn 3. Memoirs of the Botanical Survey of South Africa No. 57.
  • VAN WYK, B. & VAN WYK, P. 1997. Field guide to trees of southern Africa. Struik, Cape Town.
  • PALMER, E. 1977. A field guide to trees of southern Africa. Collins, London & Johannesburg.
  • COATS PALGRAVE, K. 1981. Trees of southern Africa, edn 2. Struik, Cape Town.
  • LUMLEY, M. J. & OLIVER, I. B. 1986. Cultivation of Rhus erosa and Tarchonanthus camphoratus. Veld & Flora 72: 112, 113.
  • MOFFETT, R.O. 1993. Anacardiaceae: Rhus. Flora of southern Africa, Vol. 19, Part 3, Fascicle 1, National Botanical Institute, Pretoria.


Peter Gavhi
Free State National Botanical Garden
With additions by Yvonne Reynolds
October 2002
Updated July 2008


To find out if SANBI has seed of this or other SA species, please email our seedroom.
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