Umbrella Thorn, samur

Acacia tortilis ssp. spirocarpa is one of four geographically demarcated subspecies of A. tortilis, which is ubiquitous in arid regions of Africa and widespread in Saudi Arabia, where it is known as samur. The ssp. spirocarpa is restricted to eastern Africa, with scattered occurrences on sand dunes and rocky hillsides, on deep alluvial calcareous soils, often indicating a higher water table or drainage lines. It can also occur on lateritic gravels and saline soils, and will colonise disturbed sites. This species dominates some savannah communities and provides an important source of forage. A tall, flat-topped tree, under optimal conditions, it tolerates the severe desert environment – in Africa, its range often extends into the Sahara desert – although vulnerable until established, it is hardy to frost, With multiple spreading trunks and the typical silhouette of an inverted triangle, A. tortilis ssp. spirocarpa is easily recognised by its flattened, spreading crown and hairy branchlets and pods. Young branchlets and leaves are densely pubescent. It also has spirally twisted pods, long straight stipular spines and whitish fragrant flowers. Propagation is the same as A. tortilis ssp. raddiana. It is also planted as a hedge and used for sand dune stabilisation and shelterbelts. Irrigation is necessary until well-established, but deep watering during the summer will enhance growth. Low maintenance only, except for pruning to improve appearance, it can be trained as a standard single leader tree.