Common Name: African Oil Bean

General Information

Pentaclethra macrophylla is a relatively fast-growing evergreen tree growing from 20 - 40 metres tall[]. It has a characteristic low branching habit and an open crown, which allows substantial light under its canopy[]. The stem form is usually crooked and buttressed, though some straight-stemmed and less buttressed trees, which can pass for good timber, are occasionally seen in the forests[]. The bole can be around 1 metre in diameter[].
An important multipurpose tree for local people, providing food, medicines and a range of other commodities[]. It is often left when other trees are cleared and is planted, mostly along roads, in Africa. It is sometimes also used as a shade tree and is grown as an ornamental[, ].

Known Hazards

The seeds contain a toxic alkaloid[]. They are pulverized and used as a component of an arrow poison, they are also used as fish poison and as mild drug (snuff)[].

Botanical References

Range

West tropical Africa - Senegal to Central African Republic, south to Angola and the Congo.

Habitat

Mainly in lowland rainforest, but also sometimes in the high forest zone[]. Often occurs near streams and on the edges of damp depressions, and is frequently seen as a small tree of untidy habit and large crown on roadsides and farms[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	30.00 m
Growth Rate	Fast
Pollinators	Bees
Cultivation Status	Cultivated, Ornamental, Semi-cultivated, Wild

Cultivation Details

A plant of the humid and subhumid tropics[]. It grows best in areas where the mean annual temperature is within the range 24 - 30°c, but can tolerate 18 - 34°c[]. It prefers a mean annual rainfall in the range 1,800 - 2,200mm, tolerating 1,000 - 2,700mm[].
Succeeds in full sun and in light shade[]. Prefers a deep, moderately fertile medium soil[]. Tolerant of some water-logging[]. Prefers a pH in the range 4.5 - 5.5, but tolerates 4 - 6.5[].
Seedling trees can reach a height of 1.5 metres by the end of their first year[].
The trees start to produce beans from their tenth year and will continue to bear regularly[].
After about 2-years growth in the forest, the trees become relatively fire resistant and resprout readily when lopped[].
Trees coppice well and often produce watershoots around their base[].
There are conflicting reports on whether or not this tree has a symbiotic relationship with certain soil bacteria, so it is unclear as to whether this tree fixes atmospheric nitrogen[].

Edible Uses

Seeds - boiled or roasted[, , ]. They can be ground into a flour and used in making bread[]. The pods are 40 - 50cm long and 5 - 10cm wide, containing 6 - 10 flat, glossy brown seeds up to 7cm long[, ].
The seeds are fermented to produce 'ugba'[]. They are boiled for 3 - 12 hours; then the seedcoat is removed. When the cotyledons are cooled to room temperature they are sliced into small pieces of 4 - 5 cm × 1 - 2 mm and washed with water. The slices are boiled for 1 - 2 hours, cooled and soaked in water for 10 hours[]. Then the slices are drained in a basket lined with banana leaves[]. The drained slices are wrapped in blanched leaves of banana or Mallotus oppositifolius and incubated at ambient temperature for 4 - 6 days when prepared for use as a snack or sidedish, or for 7 - 10 days when prepared as a condiment for soups[]. The fermentation is proteolytic and proceeds under alkaline conditions. It is caused mainly by Bacillus subtilis, but other Bacillus spp. are also involved, while other bacteria may be present as contaminants[].

The seeds contain 30 - 36% of an edible oil[]. They are used for the production of 'owala-oil', or 'owala-butter' which is used in food[].

The ash of the seedpods is used as a salt substitute[].

Medicinal

Extracts of the leaf, stembark, seed and fruit pulp have anti-inflammatory and anthelmintic activity, and are used to treat gonorrhoea and convulsions, and also used as analgesic[].

The crushed seeds are taken to acquire an abortion[].

Leaf and stem decoctions are taken against diarrhoea[].

A lotion made from the bark is used as a wash on sores[].

The ripe fruits are applied externally to heal wounds[].

The root bark is used as a laxative, as an enema against dysentery and as a liniment against itch[]. An infusion of the bark is used as an abortifacient[].

Agroforestry Uses:

Farmers protect this species on farms because of its open crown form that allows substantial light and does not inhibit crop plants grown under its canopy[]. This accounts for the trees use in combination with food crops on farms and particularly in home gardens in south east Nigeria[]. The tree produces a heavy leaf fall and these are used as a mulch[].

Other Uses

The seeds contain 30 - 36% oil[]. They are used for the production of 'owala-oil', or 'owala-butter' which is used in soap and candle production[].

The dried pods are used as fuel[].

The ashes of burnt pods are used as a mordant[, ].

The seeds are decorative and are used as beads in necklaces and rosaries[].

The heartwood is reddish brown and not always distinctly demarcated from the whitish or grey sapwood[]. The wood is hard, the grain interlocked and difficult to work[, ]. Wood of suitable size can be difficult to find but, when available, it is used for turnery, wheelwright's work, fencing, railway sleepers and general carpentry[, ]. Traditionally, it is used to make pestles and mortars[].
The wood is used as firewood and charcoal[].

Propagation

Seed - best sown as soon as it is ripe because it has a short viability[]. Storage at 15°c can extend longevity for about three months[]. Scarifying the seed and then soaking for 24 hours in warm water prior to sowing increases the germination rate and reduces the time taken to germinate[]. About 87% of treated seed germinates within 14 - 16 days[].
Adult trees can be air layered[].
Cuttings of juvenile plants can be rooted, but usually require rooting hormone[].

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