Pycnanthus angolensis

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100 of the World's worst Invasive and Alien Species.




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Local names:
English (pycnanthus,false nutmeg,cardboard,boxboard,African nutmeg), Igbo (oje,akwa-mili), Luganda (munaba,lunaba), Spanish (calabo), Trade name (pycnanthus,lunaba,ilomba), Yoruba (akomu)

Pycnanthus angolensis is a tree to about 25-35 (40) m high and 60-100 (150) cm in diameter, occasionally more, evergreen; bole straight, cylindrical, without buttresses; bark grey, longitudinally fissured, flaking in patches, in old trees; slash reddish, exuding a sticky, honey-coloured sap turning red. Branches in whorls; twigs and foliage covered in rust-coloured felt.

Leaves 18-31 x 5-9 cm, usually with the margins nearly parallel, acuminate at apex, cordate at base, leathery, glabrous on the upper surface, densely covered beneath with a short rust-coloured felt which wears off with age. The leaves are so often eaten by insects that this is a characteristic feature; the midrib is very prominent beneath with the lateral nerves running at a wide angle to it and lopped close to the margin; stalk stout, about 1.3 cm long.

Flowers densely clustered at the ends of irregularly-branched panicles 7.5-15 cm long, upright among the leaves or slightly below them; branches stout, rust-coloured. Individual flowers cannot be easily distinguished, the clusters appear as a rust-coloured mass, but the stamens are conspicuous after the male flowers open. 

Fruits (often occurring within the flowers) ellipsoid or almost spherical drupe, 2.5-3.8 cm long and 1.9-3.2 cm in diameter, often in dense clusters at the base of the twigs, opening by 2 valves and exposing a solitary black seed with a bright red aril much branched at the apex.

The generic name, Pycnanthus is derived from Greek, the literal meaning is ‘dense flowers’ and it refers to the numerous flowers crowded together.

Ecology

P. angolensis is found in the moist lowland rainforests from West Africa to Uganda and Tanzania. The tree is mainly found in scattered fashion in the secondary formation of evergreen and semi-deciduous forests. When frequent in closed high forest it is usually an indicator of old secondary forest. It does not colonize in quantity but occurs as individuals in forest gaps and clearings. The boundaries of its natural range correspond to its minimum rainfall and a dry season of 3-5 months.

Native range
Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Congo, Cote d'Ivoire, Gabon, Ghana, Guinea, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, Tanzania, Togo, Uganda

Tree management

P. angolensis is a sun-loving species with a medium rate of initial growth and an overall fast rate of growth. It reaches a height of 0.5 m in 1 year and 3-4 m in 4 years. At the age of 10 years the average height is 12-15 m, and reaches 20-25 m in 20 years. Early pruning is recommended. 
The recommended planting density is 1 100 stems/ha. The first thinning should be carried out when the trees are about 7 years old to reduce the density to 300-350 stems/ha. Toward the age of 12 years a second thinning reduces density to 150-200 stems/ha. On good evergreen forest sites, the exploitable diameter of 50 cm is reached around the age of 30 years and that of 60 cm toward 45 years. At 15 years the mean volume increment is 15 m³/ha/year and at 30 years it is 10 m³/ha/year.

Seed storage behaviour is orthodox. There are about 500 seeds/kg.

P. angolensis is found in the moist lowland rainforests from West Africa to Uganda and Tanzania. The tree is mainly found in scattered fashion in the secondary formation of evergreen and semi-deciduous forests. When frequent in closed high forest it is usually an indicator of old secondary forest. It does not colonize in quantity but occurs as individuals in forest gaps and clearings. The boundaries of its natural range correspond to its minimum rainfall and a dry season of 3-5 months.

Soaking in cold water for 24 hours will hasten germination. Germination is hypogeal. The germination period is from 16-36 days. Seeds are sown in pots.
The young plant very rapidly grows a large taproot whose development must be checked in the nursery. Care must be taken to avoid cutting the taproot if it is large because its destruction greatly reduces the plant’s rate of growth.

The seeds burn like candles and seed oil is used as an illuminant in West Africa.

Timber:  Wood is greyish-white or tinged with pink. It is light, very soft, of medium nervosity and shrinkage. Its natural durability is low, but it is easy to impregnate; mechanical properties are medium and it is easily machined. During seasoning the wood sometimes warps. This easily worked, and straight-grained wood is used for veneer peeling, panels, furniture frames, box-making and minor joinery. In Cameroon it is split into rough planks for house building and roofing materials.

Shade or shelter:  In Uganda P. angolensis is often planted as a shade for bananas, coffee and cocoa.

Lipids:  Oil is extracted from the seeds and is used in making soap. 

Medicine:  Bark decoction is an emeto-purgative and can act as an antidote to poisoning; help treat leprosy and, if pounded, used for stomachic. Sap acts as a syptic (arrests bleeding). Leaf and bark help to relieve toothache. Leaf decoction as a drink or enema for dropsy. Seed fat and probably leaf juice is used in treating thrush. Root infusion acts as an anthelmintic.