General Info

Tree is up to 9m high. Bark is dark and irregularly fissured. Leaves are trifoliate and alternate. Small, yellowish, unisexual, regular Flowers are in panicles. The Fruit is a small drupe with 1 Seed.

Description

Tree

Searsia lancea, Rhus lancea, Rhus viminalis.

RSA Tree No. 386. DNA research has confirmed difference between European Rhus and our Searsia.

Common names: Karee, Bastard willow, Karoo tree, taaibos, Rooikaree.

Family: Anacardiaceae (Mango family), which has about 83 genera and 850+ species – including Cashew). Resin canals are present and woolly stellate hairs cover all young parts. Leaves lack stipules. They are deciduous or evergreen and usually alternate. Leaves are simple, trifoliate or digitally compound and imparipinnate. When present, leaflets are usually opposite. Crushed leaves may smell of turpentine. Trees are monoecious or dioecious with occasional bisexual Flowers. Flowers are small, usually regular and unisexual. The Calyx has 4-7 sepals and there are 4-7 Petals. The number of Stamens is the same as, or twice the number of petals and the Anthers are versatile. The superior Ovary has up to 4 locules, each with a single ovule. The 1-5 Styles are free or connate and separated at the base. Fruit is usually an indehiscent fleshy drupe with a single Seed. The southern Africa genera include Harpephyllum, Lannea, Loxostylis, Ozoroa, Sclerocarya and Searsia.

Name derivation: Searsia named after Paul Sears an American ecologist (December 17, 1891 – April 30, 1990). lancea – lance-like (shape of leaflets). There are a many species of the genus Searsia in southern Africa.

Conservation Status: LC (least concern). 2009.

Tree is well-rounded and up to 9m tall and has a spread of 6m or more. The Bowl may be twisted and crooked. The plant may also develop into a scrubby bush. The Bark is dark brown to blackish. It is rough, irregularly fissured and often twisted in older trees. Branches tend to droop and are reddish brown.

Leaves

The Leaves are alternate and trifoliate (compound leaves with 3 leaflets) and are spirally arranged. Each Leaflet is fairly stiff and linear to narrowly lanceolate (lance-shaped). Except in very cold conditions, this tree is evergreen and only sheds old leaves when the new leaves appear. Leaflets have a resinous smell when crushed. The central leaflets are the longest – up to 13 x 1,2cm. Leaflets may be slightly sickle-shaped. The hairless, slightly stiff, smooth and leathery leaves are dark, shiny green above and slightly paler below. A shiny resinous exudate is often present. Lateral Veins are best viewed with the aid of a hand lens against a light. In this way, a large number of close-together parallel lateral veins can be seen. These veins may loop around and join up before reaching the margin. The Midrib is raised on both sides. The lateral veins protrude slightly on the upper side. On the lower side, only the midrib protrudes and the net veins are more obvious. The Apex is narrowly tapering, may be mucronate (ending in a small hair like tip). The Base is narrow and tapering to cuneate (wedge shaped). Margins are usually entire (with a continuous margin, not in any way indented but may be hairy) and untoothed. The thin Petiole (leaf stalk) is up to 4cm long. It is not winged and slightly grooved above – close to the blade. Petiolules (leaflet stalks) and Stipules (basal appendage of the petiole) are absent.

Flowers

The unisexual Flowers are actinomorphic (regular, symmetrical. The Perianth, the calyx and corolla are divisible into 3 or more identical sectors). The trees are dioecious (male and female flowers occur on separate trees). The sweetly scented flowers are very small, pale yellow-green and arranged in Panicles (indeterminate, branched inflorescence with stalked flowers). These axillary or terminal sprays are up to 9cm long. Each flower has 5 Sepals which are joined at the base and the 5 Petals are free. In Male Flowers the 5 Stamens have free filaments. Their Anthers have 2 Thecae (pollen sacs) present and dehiscence is longitudinal. An ovary is lacking but a rudimentary pistil is present. The Female Flowers have a single Pistil (a unit of the Gynoecium, the female element of the flower which is composed of the Ovary, Style and Stigma). The superior Ovary has 3 free Styles (Photo 159). Usually 5 Staminodes (sterile stamens) are present. (Apr-Sep).

Fruit

Fruit is a small compressed Drupe (a fleshy, 1-seeded indehiscent fruit with the seed enclosed in a stony endocarp; stone fruit e.g. peach) with a thin fleshy layer. It is almost spherical, often slightly asymmetric, about 4-6mm in diameter. A persistent recurved Calyx is visible (photo 1196). The fruit changes from green to a reddish brown and finally to a dull whitish yellow or brown. (Sep-Jan).

Distribution & Ecology

This is a Kimberley street tree. It can live for a 100 years or more. This tree is a survivor. It is drought, termite and frost resistant. Leaves are browsed by many animals – especially in the dry season. It is found in most of RSA including the Western Cape, Eastern Cape, Free State, Gauteng, Limpopo e.g. Pilanesberg, Mpumalanga, Northern Cape, North West. It is not common in KwaZulu-Natal. It also occurs in Zimbabwe, Botswana and Zambia. This tree often grows together with Acacia karoo (Vachellia karroo). It is most noticeable in arid areas near water although it roots do no not penetrate as much as Acacia karoo. It therefore is found closer to water.

Ethnobotany

It is a possible indicator of underground water. It is reported to have non-invasive roots. The red-brown close grained Wood is hard, dense (up to 970kg per cubic metre at 10% moisture content) durable and polishes well but may splinter. Flowers attract bees and other insects and, as a result, even more Birds. Birds include bulbuls, francolins, and guineafowl. Fruit is edible but not much sought after by man. The fruits are usually rubbed between the hand to remove the tough skin before they are being eaten, or they may be soaked in milk. The fruit makes good Beer when pounded with water and allowed to ferment. It is also used as a good poultry food. However our parrot (African grey) was not very impressed. Kudu, roan antelope and sable antelope do browse the Leaves. The supple branches were once used by Bushmen to make their bows. The tree can be used as a wind barrier and serves as a protection for frost sensitive shade plants. Branches are used as fence posts. The Bark has in-vitro antibacterial activity. It has been introduced into desert regions in the USA (here it is called African sumac or willow rhus) and to Mexico.

References

Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.

Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.

Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.

van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.

 

http://plantzafrica.com/plantqrs/searsialancea.htm

http://redlist.sanbi.org/species.php?species=5522-71

https://en.wikipedia.org/wiki/Paul_Sears

http://www.greenaplanet.co.za/blog/searsia-lancea-karee-a-practical-tree

https://en.wikipedia.org/wiki/Rhus_lancea

http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=12012

http://www.prota4u.org/protav8.asp?en=1&p=Searsia+lancea

http://posa.sanbi.org/flora/browse.php?src=SP