The ayo plant is a huge sprawling shrub with extremely prickly stems up to 15 m long. It forms impenetrable thickets in open disturbed areas of forest and bush in West Africa and can be planted as hedging. The leaves are bright yellow-green and up to 80 cm long, divided into leaflets which in turn are subdivided into pointed elliptic leaflets up to 4.5cm long.
Spikes of yellow five-petalled flowers are produced throughout the year, followed by fat prickly pods, 7 cm long and 4 cm wide, containing two shiny grey seeds which resemble stones. This hard smooth texture is waterproof, enabling them to survive being washed along in river or ocean currents for a year or more. Germination takes place only when the seed coat is chipped or wears thin, by which time the embryo may be far from the parent plant.
The seeds are used as counters in games such as ayo, which gets its name from this plant, and are also popular as beads. Traditionally, extracts of leaves, bark and roots are taken to lower fever, relieve skin eruptions and headache, and to expel worms in children. Scientific research shows that compounds in the seeds have antimalarial, antidiabetic, antibacterial and antifungal effects, while extracts from roots and foliage have antiviral and anticancer effects. Ayo is also a dye plant. Like other kinds of Caesalpinia, it contains pigments that produce shades of red, purple and blue. Commercially these woods are known as Pernambuco wood.
Ayo plants are found in many parts of the tropics but in some areas are scarce through over collection. Though once common in the IITA forest, they were unsustainably harvested. Numbers are now increasing, thanks to a propagation program.