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Acacia tortillis
Umbrella thorn

(drawing to come)

Origin

Sahel, Middle East to Yemen.

Ecology

Annual rainfall: 50-1000mm.

Normal temperature range: 0-45C.

Altitude range: up to 1000m.

Seasonal adaptability: dry season 6-9 months. moderately frost resistant after about 2 years old.

Soils: well drained eroded sites, sandy loams, lateritic gravel of neutral to alkaline pH. Also grows on shallow and saline soils.

Light requirement:  light demanding.

Other site limitations:  young plants are frost sensitive.

Description

Height at maturity:  4-20m.

Form: poor, multistemmed trees are common; crowns spreading.

Coppicing ability: good.

Growth: 1m in height and 1.3m in diameter per year.

Other:  stem and branches dark brown, bark deeply furrowed and scaly. Has long, white paired thorns 2-10 cm long and also short paired prickles outside leaf axils. Pods 5mm wide, 8-12 cm long, curved and twisted or spirals. Flower clusters white, cream or pale yellow, globular, 1-4 at leafbase. Leaves bipinnate, 1.5-3.5 cm long.

Primary advantages

Drought resistant, multipurpose tree with relatively good growth for arid regions.

Primary disadvantages

Seeds can be attacked by insects. Susceptible to livestock grazing when young. Timber attacked by wood borers. The tree can become a weed.

Products and yields

Wood products: fuelwood, charcoal, poles, household utensils.

Fuelwood:  4400 kcal/kg, Can yield 54 tonnes/ha in 12 years planted at 3x3m.

Fodder: leaves (15-20% protein), pods (19% protein)/seeds are an important fodder source. Production about 900kg/ha/yr.

Other: bee forage, tannin from bark, medicinal use for leaves/bark, soil conservation, dune fixation, ornamental.

Propagation

Mainly from seed, also cropping, direct seeding, natural regeneration.

Seed treatment

Store at ambient temperature. Pretreatment: dip in hot water then soak overnight, or soak in concentrated sulphuric acid for 20-30 minutes. Digestion by animals also helps germination.

Management

Establishment requires weeding, wide spacing (10x10) on shallow soils and protection from grazing for 3-5 years. Coppicing, lopping and pollarding are used for harvesting. Rotationi is 10 years for fuelwood.

Agroforestry uses

Homegardens, pastoral systems, living fences, trees-on-farm.

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