Prota 7(2): Timbers/Bois d’œuvre 2
Engl. & Prantl, Nat. Pflanzenfam. III, 8: 45 (1894).
Parasol tree (En).
Origin and geographic distribution
Polyscias fulva is widespread from Guinea east to Ethiopia and Kenya, and south to Angola, Zimbabwe and Mozambique, but it occurs mainly in mountain regions.
The wood is used for interior joinery, doors, utensils, musical instruments, containers, boxes, crates, beehives, carvings, matches, veneer and plywood. In Cameroon it is valued for carving to make handicrafts and masks, and in Uganda for making drums. It is also used as firewood, although of low quality.
In traditional medicine in DR Congo, bark infusions or decoctions are taken for the treatment of fever and malaria, as an enema to treat colic, and as a purgative. A bark maceration is applied as drops to the nostrils to treat mental illness. Pulverized bark is snuffed as anodyne, and to treat cough, haemoptysis and tuberculosis. In Cameroon the bark is used in mixtures with other plants to treat epilepsy. Leaf decoctions are taken to treat intestinal complaints including those caused by parasites, whereas pounded leaves are applied externally to treat fractures and internally against peptic ulcers. Leaves make good mulch, and the tree is suitable for intercropping with banana, coffee and cocoa. It is planted in life fences. The flowers are a good source of nectar and pollen for honey bees.
The heartwood is whitish to pale yellow-brown, and indistinctly demarcated from the sapwood. The wood is soft and brittle. The grain is usually straight, texture moderately fine to rather coarse. The wood has no distinct smell. The wood is lightweight, with a density of 330–450 kg/m³ at 12% moisture content. It is fairly easy to air dry, but splitting and ring shaking may occur.
At 12% moisture content, the modulus of rupture is 61 N/mm², modulus of elasticity 8625 N/mm², compression parallel to grain 29 N/mm², cleavage 12.5 N/mm and Chalais-Meudon side hardness 1.3. The wood is easy to saw and work, but often planes to a rather woolly surface. It is liable to splitting upon nailing and screwing, but glues well. The wood is not durable; it is susceptible to attacks by fungi such as blue stain and brown and white rot, but it is easy to treat with preservatives.
Some triterpene glycosides have been isolated from the stem bark. One of these, α-hederin, showed antifungal activity against Candida albicans and Cryptococcus neoformans.
Deciduous medium-sized tree up to 30 m tall; bole branchless for up to 15(–25) m, straight and cylindrical, up to 100 cm in diameter; bark surface grey, smooth, with lenticels, inner bark whitish; crown umbrella-shaped, with main branches often whorled, bending upward; branches with prominent leaf scars. Leaves arranged spirally, clustered at ends of branches, usually imparipinnately compound with (3–)5–12(–15) pairs of leaflets; stipules absent; petiole up to 25 cm long, slightly grooved; petiolules up to 8(–14) mm long; leaflets ovate to oblong or lanceolate, 6–20 cm × 2–10 cm, rounded to slightly cordate at base, acute to acuminate at apex, margins entire to slightly wavy, papery to leathery, yellowish brown hairy below, pinnately veined. Inflorescence an axillary panicle up to 70 cm long, yellowish hairy. Flowers bisexual, regular, 5-merous, creamy to greenish yellow, honey-scented; pedicel 1–3 mm long, jointed; calyx with very short teeth; petals free, ovate, 1.5–2 mm long, early caducous; stamens alternating with petals; ovary inferior, 2-celled, styles 2, 0.5–1 mm long, persistent in fruit. Fruit an ovoid drupe-like berry up to 6 mm long, flattened, ribbed, purplish black, glabrous or slightly hairy, 2-seeded. Seeds ovoid, slightly compressed, 3–4.5 mm long, ribbed, glabrous.
Polyscias fulva is fast growing. In plantations in Cameroon seedlings reached a height of 2(–3) m after 4 years and 15 m with a bole diameter of 20(–40) cm after 20 years. The flowers are pollinated by insects such as bees and flies.
Polyscias comprises more than 100 species and is distributed in tropical Africa, Asia, Australia and islands in the Pacific Ocean. Mainland tropical Africa has about 10 species and Madagascar about 50.
The wood of Polyscias kikuyensis Summerh., a medium-sized tree up to 25 m tall with a straight bole up to 120 cm in diameter and endemic to central Kenya, is similar to that of Polyscias fulva and used for similar purposes, especially for food containers, boxes and plywood. In Madagascar the wood of some Polyscias spp. is used by the local population, and is known together with the wood of several other genera of Araliaceae as ‘voantsilana’. One of these is Polyscias ornifolia (Baker) Harms, a small to medium-sized tree up to 20 m tall, the wood of which is heavier (density about 630 kg/m³ at 12% moisture content), stronger and harder than that of Polyscias fulva, and locally used for light construction and flooring, as well as for matches.
Polyscias fulva is found in different types of forest up to 2450(–2750) m altitude, often in secondary forest, also in mountain grassland and in vegetations dominated by bamboo. In West Africa it seems to be confined to mountain areas. The mean annual rainfall in its area of distribution is 1500–2000 mm. Polyscias fulva is sometimes considered a pioneer species, but in Cameroon natural regeneration seems to be rare. It is sensitive to fire, but may recover by producing sprouts and suckers.
Seeds and cuttings are used for planting. One kg contains about 300,000 seeds. The seeds germinate after 5–7 weeks, with a germination rate of up to 75%. Fruits can best be collected from the trees as soon as they have become purplish black, but they are sometimes also collected from the ground. They should be dried in the shade for 1–2 days. Then the fruits should be soaked in water for 4–6 hours and the seeds squeezed out; they float in the water. After drying the seeds in the shade, they can be stored for up to 2 years, preferably at 3°C and 7–10% moisture content. Seedlings are gradually exposed to the sun and can be transplanted from the nursery into the field after 4–6 months. Wildlings are commonly collected for planting.
The logs are susceptible to attack by blue stain fungi directly after felling, and should be treated with anti-stain solution or transported from the logging area and processed immediately.
Genetic resources and breeding
Polyscias fulva has a very wide distribution area, but it is uncommon in several regions, e.g. in West Africa. In Kenya it has been reported that Polyscias fulva is becoming rare in its natural habitat. This is also locally the case in Cameroon and Uganda, where the species has been overexploited for the production of handicrafts. Monitoring of populations in such regions where it is under pressure because of timber harvesting is recommended, but Polyscias fulva is not yet subject to serious genetic erosion, as is the case in Kenya with the endemic Polyscias kikuyensis that is already included as vulnerable in the IUCN Red List.
Although the wood of Polyscias fulva is of rather poor quality for building purposes, it seems to have good prospects for commercial production of carvings, veneer and plywood. The fair growth rates and the development of a long and straight bole are advantageous. Polyscias fulva has good characteristics as a shade tree and auxiliary plant, which make it interesting for agroforestry systems. In Uganda it has already been recommended to start on-farm production of Polyscias fulva to guarantee future supply of the wood for purposes for which it is much in demand, such as drum production. However, research is still needed on propagation techniques and on growth and development.
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Correct citation of this article:
Lemmens, R.H.M.J., 2009. Polyscias fulva (Hiern) Harms. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.