Gum Arabic Tree

The gum arabic tree (Acacia senegal, now often placed in the genus Senegalia as Senegalia senegal) is a small, thorny, intensely drought-hardy legume of Africa’s drylands.123 It is native to the semi-desert regions of sub-Saharan Africa and also occurs in Oman, Pakistan, and west-coastal India, with a wide African range running from Mauritania and Senegal east to Sudan, Ethiopia, and Kenya and south to Tanzania and Mozambique.12 For a homesteader on hot, sandy, marginal ground, its appeal is straightforward: it is one of the few woody plants that establishes on near-desert soil, fixes its own fertility as a legume, and still yields a saleable crop — gum arabic, the hardened sap tapped from the bark and used as a food additive and dietary fibre.124

It is a deciduous shrub or small tree, typically 2 to 6 m tall and occasionally reaching up to about 15 m, with a flat to rounded crown; some sources describe it at 5 to 12 m with a trunk up to 30 cm across.12 It is usually low-branching with several stems, its branches carry the short, sharp thorns characteristic of the acacias, and the bark is pale to grey, roughening with age.12 Leaves are bipinnate (twice-divided into many small leaflets), the typical form of the mimosoid legumes, and the tree drops them through the long dry season.12 The flowers are small and cream to whitish, borne in dense spikes, and are followed by flat pods holding several seeds.12

Growing gum arabic tree

The standard method is propagation by seed. In nursery production, seed is sown in polyethylene pots at 2 to 4 seeds per pot and thinned to a single seedling after about 4 to 6 weeks.1 For direct seeding on site, 5 to 8 seeds are sown into prepared pits of roughly 30 by 30 by 30 cm (or larger).1 Trees go in as bare-root or potted seedlings, the way the agroforestry “gum gardens” of Sudan are established.15 Like many acacias the seed generally responds to pre-treatment such as scarification, but the sourced material does not spell out a specific treatment for this species, so none is invented here.

This is a plant for the harshest, driest sites. It is very drought-resistant and grows across an annual rainfall band of roughly 100 to 950 mm — most commonly around 300 to 400 mm — and copes with dry seasons lasting 5 to 11 months.1 It tolerates very high mean maximum temperatures of 45 °C or more, along with dry winds and sandstorms.1 For soil it prefers coarse, sandy ground such as fossil dunes, but also takes slightly loamy sands and shallow, skeletal, rocky soils (Lithosols), and in the Sudanese gum belt it is found on sandy hills and sometimes on heavy “cotton” clays.15 The primary sources describe its climate but do not assign USDA hardiness zones, so no zone number is stated here; in practice this is a frost-free, very warm-climate tree adapted to hot semi-arid country.12

Harvest and uses

The signature product is gum arabic: the tree exudes hard, translucent nodules — pale yellow to reddish — from cuts in the bark, and a typical tree yields on the order of 200 to 300 g of gum per season.2 Gum arabic is an approved food additive and a source of dietary fibre, which is the main commercial reason the species is cultivated, particularly across the Sahel and similar drylands where it is a key agroforestry tree.1 Beyond the gum, the seeds are eaten as a vegetable in some regions, and the tree carries broad ecological and agroforestry value as a hardy dryland legume.1 As a nitrogen-fixing pioneer it suits the role of a soil-building first species on degraded, sandy, or dune ground where more demanding plants cannot start.1

How to identify it

Look for the combination of features that distinguishes this acacia in dry country:12

• Habit: a low-branching, often multi-stemmed thorny shrub or small tree, commonly 2 to 6 m (occasionally taller), with a flat to rounded crown.
• Thorns: short, sharp spines along the branches, typical of the acacias.
• Leaves: bipinnate, made up of many small leaflets, and shed during the long dry season.
• Flowers: small, cream to whitish, packed into dense spikes.
• Fruit: flat pods containing several seeds.
• Gum: hard, translucent, pale-yellow-to-reddish nodules oozing from wounds in the pale-grey bark.

Safety and cautions

Gum arabic from Acacia senegal has relatively low documented toxicity when used as gum in normal food amounts, and it is an approved food additive.1 That said, the tree is armed with sharp thorns, so handle prunings and tapping work with appropriate care. The edible uses recorded in the sources are specific — the gum and, in some regions, the seeds used as a vegetable — and other parts of the plant should not be assumed edible on that basis.1 This profile describes traditional and commercial uses only and makes no medical claims.

Sources

1. Acacia senegal: A Gum Tree with Promise for Agroforestry – Winrock FACT Net
2. Senegalia senegal – Wikipedia
3. Acacia senegal – iNaturalist
4. Gum arabic tree (Acacia senegal) – Feedipedia (INRAE, CIRAD, AFZ & FAO)
5. Acacia senegal gum gardens and agroforestry in Sudan – Tropentag 2008