Acacia tortilis is common in most of dry Africa, from North and West to the South of the continent. In Kenya, it is widespread in lowland arid and semi-arid regions.
The altitude ranges from 0 to 1,650 metres above sea level and annual rains of 150-900mm, according to Kenya Forestry Research Institute’s (Kefri) Guide to Tree Planting in Kenya.
Benefits
This acacia has many uses, which include firewood, timber, charcoal, poles, edible pods, medicine, fodder (pods and leaves), bee forage, shade, dune fixation, nitrogen fixation, soil conservation, fibre (from bark), live fence and dye. Its thorns are used as pins or needles.
Fodder
Acacia tortilis’s leaves and pods make nutritious fodder for herbivores. The pods are collected and saved for the dry season and even sold in northern Kenya.
A 10-year-old tree yields up to six kilos dry leaf and 12kg of pods per year. The foliage is a favourite for sheep, goats, camels, cows and wildlife. The leaves are fed green as well as dry.
Crude protein in the leaves and pods is as high as 18 per cent while digestibility is 46.2 per cent.
They also have high levels of carbohydrates at 46.2 per cent, minerals (5.1 per cent) and crude fibre 20.1 per cent, according to the Indian Council of Forestry Research and Education.
Environment
This acacia species helps in nitrogen fixing, thus is a soil improver, according to the Food and Agricultural Organization.
It is used in erosion control since it grows quickly and stabilises shifting sand dunes or hill slopes. In India, it is used to make shelterbelts along highways, railways and farms.
Acacia tortilis is particularly suitable for fuel wood. Its dense, red hard wood has high calorific value making superior firewood and charcoal. The tree starts giving fuel wood at the age of eight to 10 at the rate of 50kg/tree.
Twigs, branches and thorns are used as fencing materials. Bigger branches are used as poles for erecting fences around farms and plantations.
It is a sustainable source of fuel wood, because it is fast-growing and multiple-stemmed.
Medicine
Africans have traditionally used this tree to treat a number of ailments. In Egypt, Libya, Tunisia, Algeria and Morocco, its gum is used to treat ocular infections, jaundice and pulmonary diseases.
The dried powdered bark is used as a disinfectant in healing wounds, and the seeds are taken as an anti-diarrhoeic. In Somalia, the stem bark is used in treating asthma.
In Oman, young shoots of Acacia tortilis are used for treating mastitis. In Senegal, the bark, which contains a high concentration of tannin, is used as an anthelmintic. Its powder is also used for treating skin disorders.
Its roots are made into spear shafts in Senegal, stems into fish spears by fishermen in Lake Chad and flexible roots are used to build mobile huts by the nomadic Fulani.
The bark is used to expel parasitic worms from the body and as a dusting powder for skin diseases in Guinea.
For bee farmers, the tree’s flowers provide a reliable source of honey.
If you are from Kenya’s semi-arid lowlands such as Taita-Taveta, Makueni, Kitui, Tana River, Machakos and in the north, this tree comes highly recommended.
Propagation is by seedlings, wildings and direct sowing. However, seedlings are the most popular. Seeds cost Sh2,500 a kilo at Kefri shops.
Because of its nutritious leaves, keep animals, especially goats, away from it.
Seeds of Acacia tortilis have a hard coat which is impervious to water that causes seed dormancy and the germination may extend over months or years. To ensure faster germination, pre-sowing treatment is necessary.
There are two main methods of doing this. One is the use of boiling or hot water, acids, organic solvents and alcohols, which is known as wet pre-treatment. Seeds are soaked in these liquids for a period of time, usually 12 hours.
The second method involves use of dry heat, microwave energy, impaction, percussion and manual or mechanical scarification.
Studies on seed treatment indicate that maximum germination in shortest time could be achieved by soaking the seeds in concentrated sulphuric acid for between 20 and 60 minutes.
To avoid these complicated processes, you can buy seedlings at Kefri and Kenya Forestry Service nurseries.
