Prota 7(2): Timbers/Bois d’œuvre 2
Lundell, Fl. Texas 3: 104 (1943).
2n = 30
Rhus lancea L.f. (1781).
Karee, African sumac, willow rhus (En).
Origin and geographic distribution
Searsia lancea is indigenous in Zambia, Namibia, Botswana, Zimbabwe, South Africa and Lesotho. It is planted in hedges and as ornamental tree, e.g. in South Africa, but also in desert regions of the United States and Mexico, where it is locally naturalized.
The tree boles are considered valuable as fence poles, and the wood is used for implement handles and wagon parts. Branches have been used for bows and for spars in hut building. Young twigs are occasionally used for basketry. The fruits are edible; they are pounded with water and produce a beer after fermentation, and they are also used to produce curdled milk. Searsia lancea is commonly planted in hedges, as an ornamental tree in gardens and parks, as a roadside tree and in live fences and wind breaks. Roots, leaves and stem bark are used to treat skin diseases. A root infusion is taken to treat abdominal and chest complaints and diarrhoea, and the roots are chewed against stomach-ache. Leaf decoctions or infusions are taken to treat measles and pustules, whereas leaf vapours are inhaled to cure cough. The bark and wood have been used for tanning, and the bark gives a brown dye. The leaves are browsed by livestock, especially in the dry season.
The wood is reddish brown, with a fine texture, and it is hard, tough and durable. It is heavy, with a density of 890–970 kg/m³ at 10% moisture content. The rates of shrinkage are moderate, from green to oven dry about 3.1% radial and 7.2% tangential. The wood works well and takes a nice polish. It has a sweetish and spicy smell.
Bark extracts showed in-vitro antibacterial activity against a wide range of gram-positive and gram-negative bacteria. Leaves yield 0.2% of essential oil, with α-pinene, benzene and δ-3-carene as main constituents. The oil showed remarkable anti-oxidant activity and dose-dependent antibacterial and antifungal activities. These activities may be associated with the high concentration of α-pinene in the oil (87%). The flavour of cattle milk is affected when large quantities of Searsia lancea leaves are browsed.
Evergreen, dioecious shrub or small tree up to 9(–12) m tall, glabrous; bole often twisted and crooked; bark surface dark grey to dark brown, rough, often irregularly fissured; twigs reddish brown, angular or slightly grooved, pendulous. Leaves arranged spirally, 3-foliolate; stipules absent; petiole 2–7 cm long, slender but slightly winged near apex, grooved above; leaflets sessile, narrowly lanceolate, often slightly sickle-shaped, 7–24.5 cm × 0.5–3 cm, cuneate at base, acute at apex, margins entire, thinly leathery, pinnately veined with numerous lateral veins. Inflorescence an axillary or terminal, much-branched panicle up to 9 cm long, lax. Flowers unisexual, regular, usually 5-merous, greenish yellow; pedicel 2–3 mm long; calyx segments c. 0.5 mm long, obtuse; petals free, oblong, c. 1.5 mm long; stamens usually 5, free; disk cup-shaped; ovary superior, globose, 1-celled, styles 3, thick, recurved; male flowers without ovary or with strongly rudimentary ovary, female flowers with rudimentary stamens. Fruit a depressed-globose drupe 4–6.5 mm in diameter, often slightly asymmetric, dull yellow to greyish or brown, with fleshy pulp.
Searsia lancea grows fairly fast, up to 80 cm/year in height for young trees. It flowers from April to September(–January) and ripe fruits can be found from September to February. The flowers have a sweet smell and are visited by insects such as bees, which serve as pollinators. The fruits are eaten by birds such as guinea-fowl, francolins and bulbuls, which are probably the main seed dispersers.
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.
Several other Searsia spp. produce wood that is used for similar purposes as that of Searsia lancea. The wood of Searsia glutinosa (Hochst. ex A.Rich.) Moffett (synonyms: Rhus abyssinica Oliv., Rhus glutinosa Hochst. ex A.Rich.), a shrub or small tree up to 10 m tall from Sudan, Eritrea and Ethiopia, is used for agricultural implements and tool handles, and as firewood. The leaves are used in traditional medicine to treat influenza, the roots in veterinary medicine to treat udder complaints. They have been used for tanning.
The reddish, hard and tough wood of Searsia gueinzii (Sond.) F.A.Barkley (synonym: Rhus gueinzii Sond.), a shrub or small tree up to 8 m tall occurring in Zimbabwe, southern Mozambique and eastern South Africa, is used for wall laths in house building. Branches are used to treat eye complaints; they are made into a lotion, or smoke from burning twigs is applied to the eyes. A root infusion is taken to treat schistosomiasis and a leaf decoction against gall sickness.
The stems of Searsia lucida (L.) F.A.Barkley (synonym: Rhus lucida L.), a shrub or small tree up to 7 m tall from Zimbabwe and South Africa, are valued for fence posts. The bark has been used for tanning. Ground bark is applied to ring worm infections.
The stems of Searsia pendulina (Jacq.) Moffett (synonyms: Rhus pendulina Jacq., Rhus viminalis auct. non Aiton nec Vahl), a small tree up to 10 m tall occurring in Namibia and South Africa, are used as fence posts and in hut building, whereas the twigs are used for fish traps. The bark yields a reddish brown dye. The fruits are edible and have been used in beer making. Searsia pendulina is planted as ornamental tree.
The wood of Searsia retinorrhoea (Steud. ex Oliv.) Moffett (synonym: Rhus retinorrhoea Steud. ex Oliv.), a shrub or small tree up to 6 m tall from Sudan, Eritrea, Ethiopia, Somalia and Arabia, is used for agricultural implements and walking sticks, and as firewood. The leaves serve for local mattresses. Several flavonoids have been isolated from the leaves, some of which showed weak antibacterial and antimalarial activities in vitro.
Searsia lancea occurs in grassland and open woodland, often on river banks and termite mounds. It is considered as an indicator of underground water. It seems to prefer soils rich in lime. Once established, the tree is drought and frost tolerant.
Searsia lancea is easy to propagate by seed, cuttings, truncheons and air layering. Ripe seeds should be sown in seedling trays and can be transplanted in containers when the seedlings have 2 leaves. Cuttings taken from young shoots often root successfully.
The tree boles are often crooked, and straight pieces of wood of fair length are usually difficult to obtain. Moreover, the bole of older trees is reportedly often hollow. A disease, causing leaves at the extremities of young branches to become deformed, has been recorded from the central highlands of Namibia. In South Africa the fungus Muribasidiospora indica was identified as the causal organism associated with leaf spots, a serious disease in several Anacardiaceae.
The fruits are usually rubbed between the hand palms to remove the tough skin before they are being eaten, or are soaked in milk.
Genetic resources and breeding
Searsia lancea is widespread and locally common, and is not threatened by genetic erosion.
The boles of Searsia lancea and other Searsia spp. are too small and poorly shaped to yield timber of sufficient dimensions and quality for the international market, but locally the wood will continue to be valued for e.g. fences and implements. The tree has considerable ornamental value, and has a non-aggressive root system and provides shade throughout the year with its evergreen, wide-spreading crown. The pharmacological properties of the leaf oil deserve more attention.
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Correct citation of this article:
Lemmens, R.H.M.J., 2009. Searsia lancea (L.f.) F.A.Barkley. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.