Fig 1: A 13-year-old Acacia kirkii in Kajiado North District near Kiserian. Note the undergrowth below the tree.
Fig 2: Acacia kirkii leaves and thorns
Fig 3: Acacia kirkii flowers
Fig 4: Acacia kirkii pods
Fig 5: Three-month-old Acacia kirkii seedlings
Fig 6: A thinned stand of Acacia kirkii wildlings – estimated to be about 3 years old.
The unexploited potential of acacias Fast-growing A. kirkii offers commercial promise for charcoal and firewood By Fridah W. Mugo and Beth Muchiri
A
cacia trees, which are famous for producing high quality charcoal, are perceived to be slow-growers in the arid and semi-arid lands of Kenya. While many acacias fit this description, others have been observed to be fast-growing. Leading the list of fast-growers is Acacia kirkii. It has multiple uses that range from fixing nitrogen, acting as a windbreak, providing firewood, charcoal, and can be used for land reclamation. The planting materials are easily available and the tree is easy to plant and manage. Farmers commonly intercrop the tree during the initial two years of planting. Other fast-growing acacias are Acacia xanthophloea, Acacia gerrardii and Acacia polyacantha. Indigenous tree species are better adapted to our environment and are better at conserving the environment. They produce high-quality products, especially firewood and charcoal, compared with most exotics, hence the need to promote their domestication. Unfortunately, there is very little information
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on their management and yields. This article is an attempt to promote deliberate planting of acacia trees for charcoal and firewood. For the last seven years, Kenyans have been planting various acacia trees in their farms as cash crops, particularly for producing charcoal. The species most commonly planted are A. xanthophloea and A. polyacantha. Two new additions to these are A. kirkii and A. gerrardii, both for charcoal production. The tree is also commonly used for fencing. Other uses include medicine, fodder, shade and dead fence thorny branches. The inner bark is chewed to quench thirst. Common names Acacia kirkii, or simply kirkii, is found mainly in Central, Rift Valley and Eastern provinces. It therefore has common names based on where it is found. Some of these names are - kimwea or mwea (Kamba), chepyaliliet (Kipsigis) and ol-lerai (Maasai).
Characteristics Acacia kirkii is a handsome flat-topped thorn tree growing to a height of 15m with ascending branches radiating from low down the trunk (Fig 1). The bark is brown-yellowgreen, smooth and peeling thinly in scrolls to show greenish-yellow under-bark. Thorns are in pairs, straight, up to 8cm long and greyish white in colour. The leaves are twice divided, with 6 - 14 pairs of pinnae and 7 - 20 pairs of leaflets (Fig 2). Flowers are reddish pink in buds, creamy white when fully open, in round heads (Fig 3) and slightly fragrant. The fruit develops into straight, brown pods, much constricted between the seeds, often with a raised boss above each seed and up to 9cm long (Fig 4). Distribution Acacia kirkii is widespread from West to East Africa and southwards to Namibia and Botswana. In Kenya, it is found mainly in Central and Rift Valley Provinces. It is common
Miti October-December 2011