Agroforestree Database

Local names:
 English (eru), French (koko), Igbo (okazi), Portuguese (nkoko)

Gnetum africanum is a dioecious forest perrenial liana up to 10 m long but sometimes longer; branches somewhat thickened at the nodes, glabrous. 

Leaves decussately opposite, sometimes in whorls of 3, simple, ovate-oblong or elliptic-oblong, more rarely lanceolate, 5-13 cm long, 2- 5 cm broad, attenuate at base, abruptly acuminate, obtuse or minutely apiculate, entire, thick-papery, glabrous, pale green above, paler beneath, with 3-6 pairs of strongly curved lateral veins looped near the margin; stipules absent; petiole up to 1 cm long.

Inflorescence an unbranched catkin, axillary or terminal on a short branch, solitary but male inflorescences at apex of branches often in groups of 3, up to 8 cm long, jointed, peduncle 1-1.5 cm long, with a pair of scale-like, triangular bracts; male inflorescence with slender internodes and whorls of flowers at nodes; female inflorescence with slightly turbinate internodes and 2-3 flowers at each node. Flowers small, c. 2 mm long, with moniliform hairs at base and an envelope; male flowers with a tubular envelope and exserted staminal column bearing 2 anthers; female flowers with cupular envelope and naked, sessile ovule. 

Seed resembling a drupe, ellipsoid, 10-15 mm × 4-8 mm, apiculate, enclosed in the fleshy envelope, orange-red when ripe, with copious endosperm.

This lianoid species lacks fibre-tracheids characteristic of G. gnemon. However, tori are clearly present in tracheary elements of this species.

In Africa, there are only two species, G.africanum and G. buchholzianum. The specific epithet africanum refers to its African origin.

The plant is threatened with disappearance because of intensive gathering and cultural practices which are destroying the forests which support these plants. Possible introduction into farm systems is a step in the right direction in conserving this plant.

Ecology

G. africanum is an endangered liane normally found in humid tropical forest. It is usually found with other climbers on middle- and under-storey trees, frequently forming thickets. It can also be found in riverine forest in areas that are otherwise too dry for the species. Gnetum africanum is mostly found at the periphery of primary forest and in secondary forest. It extends in distribution from SE Nigeria, to Congo and as far as Angola in the south.

Native range
Angola, Cameroon, Central African Republic, Congo, Democratic Republic of Congo, Gabon, Nigeria

Tree management

Gnetum africanum is still mainly collected from wild stands, but farmers often retain it when clearing fields. If cultivated, farmers need to provide support, e.g. by using commercial plantations of rubber trees, oil palm and other tree crops. Fences were only found to be successful when there is enough shade, and they are generally too expensive. Fully exposed plants do not grow well; their leaves are thin and pale green, and traders reject them.

G. africanum is an endangered liane normally found in humid tropical forest. It is usually found with other climbers on middle- and under-storey trees, frequently forming thickets. It can also be found in riverine forest in areas that are otherwise too dry for the species. Gnetum africanum is mostly found at the periphery of primary forest and in secondary forest. It extends in distribution from SE Nigeria, to Congo and as far as Angola in the south.

In Cameroon, propagation by seed was difficult because germination take one year or more. It is assumed that seeds need pretreatment, such as passing through the intestines of a bird, fruit bat, squirrel or other animal, before they germinate. Seed is normally found only in the tree canopy. Seed collection is thus far from easy, a further reason why Gnetum africanum is hardly cultivated. 

Methods of vegetative propagation using leafy stem cuttings have recently been developed. It is recommended that leaf blades of cuttings be trimmed in half. Nursery beds under shade and made of well-decomposed sawdust or fine river sand can be used for propagation. Ectomycorrhizae (such as Scleroderma sinnamarense) assist the roots in absorption of nutrients . After about 6 weeks the rooted cuttings are transferred to polythene sleeves, bamboo pots or other containers where they remain for a further 2-3 months. The soil mixture for these containers consists of 25% sand and some compost, supplemented with forest soil. Field planting, preferably next to a young tree or shrub, takes place at the beginning of the rainy season.

  The leaves of this species are edible, as are those of other American and Asian Gnetum species. G. africanum holds an important place in the diets of many people in central Africa. In the Congo Gnetum consumption has been evaluated at 2g /capita. Women play a great role in the gathering and selling of the much relished leaves all year round. Commerce in Gnetum has increased considerably. A company, 'Paysans Centrafricains' has exported leaves to Europe particularly France and Belgium.  It is a significant source of protein (16.5% dry wt.) carbohydrates (70.6% dry wt.), essential amino acids (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine), non essential amino acids (aspartic acid, serine, glutamic acid, proline,glycine, alanine, cysteine, tyrosine histidine and arginine) and mineral constituents i.e. macro and micro-elements (7.0% dry wt.).  It can be eaten raw, but is generally added to meat and fish dishes after cooking time. The fruit and seeds are edible.

Lipids:  The leaf fat content in gnetum is significant, up to 14.20% (Okafor et al.1996.).

Medicine:  The leaves are used to treat enlarged spleen, sore throat and also used as a cathartic. The plant provides an arrow poison antidote. In West Africa chopped leaves are used as a dressing on furuncles to hasten maturation. The stem is used in making preparations to ease childbirth.

Alcohol:  The potential of African species to yield a potable sap as the Asian species is worth investigation.

Has significant cultural value in traditional ceremonies.