Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species should retain the name Acacia, whilst other sections of the genus should be transferred to other genera. This species is transferred to Vachellia[].

Common Name: Umbrella Thorn

General Information

Vachellia tortilis is a distinctive small to medium-sized evergreen tree or shrub that develops a large, umbrella-like, spreading canopy[]. It is one of the few timber-producing species able to grow on the Arabian Peninsula[]. In good conditions it can grow up to 21 metres tall, though it is more likely to be in the range 8 - 10 metres and in marginal situations it can be a shrub as small as 1 metre tall[, ].
An important, multi-purpose tree within its native range, where it has a wide range of uses, providing food, medicines, timber, fuel, tannins etc. It is often gathered from the wild for local use, and is also used in planting schemes for soil stabilization and shelterbelts[].

Known Hazards

There are unconfirmed allegations that the foliage can be toxic to livestock[].

Botanical References

Range

Africa - semi-arid areas from S. Africa to the Sahel and also to Israel and Arabia.

Habitat

Widespread in the Sahel, in woodlands and in the savannah[]. It generally forms open, dry forests in pure stands or mixed with other species[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	15.00 m
Growth Rate	Fast
Cultivation Status	Cultivated, Wild

Cultivation Details

Umbrella thorn is a plant for semi-arid tropical and subtropical areas, succeeding at elevations from sea level to 2,000 metres[, ]. It grows best in areas where the mean annual temperature is in the range 23.4 - 31.3°c, with a mean annual rainfall of 100 - 1,000mm[]. It tolerates a maximum temperature of 50°c and a minimum temperature close to 0°c[], though trees less than 2 years old are very susceptible to frost damage[].
The tree favours alkaline soils and grows in sand dunes, sandy loam, rocky soils and other soils that drain well[]. It also does well on light brown, sandy soil with little or no calcium carbonate, and pH ranges of between 7.95-8.30[]. Tolerates pH in the range 6.5 - 8.5[]. A drought resistant plant, it can tolerate strong salinity and seasonal waterlogging[]. The long taproot and numerous lateral roots enable it to utilize the limited soil moisture available in the arid areas[]. Plants can grow fairly well in shallow soil, less than 0.25 m deep, though they develop long lateral roots that can become a nuisance in nearby fields, paths, and roadways[].
A fast-growing tree, it develops a long lateral root system and creates problems in marshy fields, paths and roadways. It grows fairly well even on shallow soils less than 25cm deep. However, the plant assumes shrubby growth and must be widely spaced for the lateral root growth[].
It responds vigorously to felling by producing numerous coppice shoots, provided there is no interference from browsing animals[]. Lopping of entire branches does not seem to affect the vitality of the tree[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

A porridge is made from the pods after extracting the seed[].

The immature seeds are eaten[].
The ripe fresh pods are eaten, but the seeds are discarded[]. The crunchy pods have a faint sweet taste[].

An edible gum is obtained from the stems[]. Of moderate quality[].

Medicinal

An infusion of the bark is drunk as a treatment for stomach ache and diarrhoea[].
The dried, powdered bark is used as a disinfectant in healing wounds[]. In Senegal the powdered bark is used as an anthelmintic and is dusted on to skin ailments[, ].

The stem is used to treat asthma[].

Seeds are taken to treat diarrhoea[].

Agroforestry Uses:

Due to its drought hardiness and fast growth, this is a promising species for afforesting shifting sand dunes, refractory sites, hill slopes, ravines and lateritic soils[]. It is the tree most recommended for reclaiming dunes in India and Africa[]. It has been grown successfully with Azadirachta indica in shelterbelts[].

Other Uses

The pods have been used as beads in necklaces[].

The source of a resin called Gomme Rouge[].

The bark is reported to be a rich source of tannin[, ].

A strong fibre is obtained from the bark[].

A powerful molluscicide and algicide, the fruits are placed in fish ponds to kill the snail species that carry schistosomiasis, without affecting the fish303].

The thorny branches are suitable material for erecting barriers[].

The sapwood and heartwood are white and lustrous, with the heartwood aging to reddish-brown. Growth rings are distinct and separated by brown lines. The wood is moderately soft, not very strong, and is readily attacked by decay-causing fungi and insects. It should be promptly converted after felling and subjected to rapid drying conditions. The timber is not durable in the open but moderately so under cover. It is used for planking, boxes, poles, moisture-proof plywood, gun and rifle parts, furniture, house construction and farm implements[]. It is believed that Noah of the Old Testament made his ark from the wood of this tree[].
The root of this tree is traditionally used to make quivers for arrows[]. A piece of wood about 40 - 60cm long is placed in the spent ashes of a warm fire and left overnight. The next morning, a short section of the bark of the root is removed at one end; a circular groove is carved into the exposed core wood; a piece of wire is wound around the groove at one end whist the other end is attached to a tree; the bark (having already been loosened from the wood by the drying action of the warm ashes) is then simply pulled whole off the root[]. The core of wood remaining is then often used as a pestle[].
The plant starts producing fuel wood at the age of 8 -18 years, at the rate of 50 kg/tree. Its fast growth and good coppicing behaviour, coupled with the high calorific value for its wood (4400 kcal/kg), make it suitable for firewood and charcoal[].

Propagation

Seed - requires pre-treatment. The simplest method is to pour boiling water over the seeds and soak the seeds in this cooling water for 24 hours[]. Commercially, scarification with 50% concentrated sulphuric acid for 40-50 minutes followed by washing in cold running water and then drying in the shade overnight is often used[]. Seeds of various dimensions have varying scarification requirements[]. This method gives the maximum germination rate, about 95%. It is further reported that older seeds give healthier seedlings compared with fresh seeds[]. The pre-treated seeds are sown in cylindrical metallic containers 10.2 cm in diameter and 30.5 cm long, filled with equal proportions of finely powdered farmyard manure, tank silt and soil that is sieved through a fine wire mesh. Two seeds are sown in each container. The sowing depth should not be more than to 4 cm; otherwise, seedling emergence will be adversely affected. Germination starts on the 4th day and is mostly completed over 10 days, although it may continue for 60 - 70 days. Germination rates can be low, around 45%[]. Seedlings should be watered twice a day. Shade, when provided during the summer months, reduces the water requirement of the plants by 9.6% as compared with those grown in the open. Seedlings raised in metallic containers and planted in cemented beds, which are immersed in water, require 29% less water than those kept in earthen beds. In the long run, metallic containers are cheaper than the other types of containers and last longer (about 12 years). Seedlings are planted out when 0.5 - 1 m high and require initial weeding to facilitate growth[]. Plants less than 2 years old are damaged by frost and are tender to hot, desiccating winds[].
Seed storage behaviour is orthodox; viability can be maintained for several years in hermetic storage at 10 deg. C with 4.5-9% mc[].

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