African Locust Bean

Parkia biglobosa

Origin:

Native to Central and West African savannahs and now also grown in a number of Caribbean Islands.

Climate:

It grows best in dry regions with annual rainfall of about 650mm pa but will survive down to 400mm and up to 1200mm in some circumstances. In its native areas it is found up to 1500m above sea level.  The ideal temperature range is 21-36°C but it can survive up to 45°C.  It is not adapted to high rainfall, humidity or frost, and usually occurs in isolated stands either domestically or in parks, or wild across the African savannahs.

Plant Description:

This deciduous tree can grow to 20m in its native habitat and has a large spreading crown. It has dark green bipinnate leaves 20-40cm long with numerous pinnae, each containing many pairs of leaflets.

Relatives:

Fabaceae, formerly called Leguminoseae.  Other fruiting plants include carob, Tahitian chestnut and tamarind.

Soils:

Like most fruit trees it is more productive with fertile soils but it can also survive on poorer soils. Once established, its deep roots maintain it under dry conditions. As a legume it has a symbiotic relationship with nitrogen-fixing bacteria which not only enriches the tree itself but the surrounding soil also.

Propagation:

Seeds are mainly used but they have an exceptionally thick seed coat. There are two types, reddish-brown which germinate easily, and the dark brown types which need pre-sowing treatment by scarification and/or soaking in water or acid. Chance selections can then be grafted on to these seedlings. Cuttings can also be used. There is considerable genetic variation in fruit shape, size, yield and quality between different trees and environments.

Cultivars:

There are no recognised cultivars, reflecting the fact that it has received almost no horticultural development.

Flowering and Pollination:

Orange-red club-shaped flower heads about 5cm in diameter are clustered on long peduncles. In dry climates the trees may be completely or partially leafless while flowering. The flowers are hermaphrodite and will produce a small crop, but this is greatly increased with cross pollination. The topmost flowers in each cluster are thought to be sterile but nevertheless produce ample nectar to attract pollinators, principally bees, flies and bats. Flowers remain open for one night and early morning only. Good soil moisture improves flowering.

Cultivation:

No studies have been undertaken on general fertilizer needs, but predictably, nitrogen fertilization does not improve growth. The tree is delicate when young and needs protection from full sunlight or drought.

Wind Tolerance:

Unknown.

Pruning:

Training and maintaining an open canopy improves fruit yield. Growers report that regular pruning increases fruit production.

The Fruit:

The fruit is a slightly bent brown dehiscent pod about 15-40cm long, hanging in clusters from the fruit base. There are 5- 20 seeds encased in a yellow-orange pulp that tastes like a rich custard.

Fruit Production and Harvesting:

The juvenile period is 5-8 years but can be less in cultivation. Pods for edible pulp are best picked from the tree; however if only seeds are desired they can also be collected from the ground after dehiscence. Mature trees can produce 20-80kg of pods pa.

Fruit Uses:

The sweet dry pulp is eaten fresh and consists of 50-60% sugars along with good levels of vitamin C. It is also dried and used in cooking. After considerable processing, seeds are fermented and used as a condiment in traditional cultures.

Pests and Diseases:

To date, these do not seem to present major problems.

Comments:

This fruit tree is still basically in its undeveloped wild form and offers the promise of major possible improvements to an already valued food.