Prota 7(1): Timbers/Bois d’œuvre 1
Syn. conif.: 26 (1847).
African pencil cedar, East African cedar, East African juniper, pencil cedar (En). Genévrier d’Afrique, genévrier d’Abyssinie (Fr). Mwangati (Sw).
Origin and geographic distribution
Juniperus procera occurs wild from Sudan, Eritrea and Ethiopia southwards through East Africa and eastern DR Congo to Malawi and Zimbabwe; it also occurs wild in Saudi Arabia and Yemen. It is grown in plantations in its native range and elsewhere, including South Africa, France, the United Kingdom, the United States, India and Australia.
The wood of Juniperus procera (trade name: African pencil cedar) is widely used for building (both construction and lining), joinery, flooring (strip and parquet), furniture and all sorts of outdoor work such as roofing shingles, fence posts, water flumes and transmission poles. In Kenya the wood is also used for making fire sticks, beehives and salt-troughs. Juniperus procera wood was exported to Europe and North America for the manufacture of pencils and penholders, while small quantities were used for wardrobe linings. It is also suitable for ship and boat building, agricultural implements, musical instruments, carving, vats, toys and novelties, turnery, draining boards and food containers. It can be used for making veneer and plywood, hardboard and particle board, and as pulpwood. The wood is used as firewood and to make charcoal.
The bark is used for roof shingles and for covering beehives. Essential oil distilled mainly from the sawdust (‘cedar wood oil’, ‘cedar oil’) is used in the cosmetic industry in soaps and perfumes. Since Juniperus procera can grow in extreme conditions, it is replanted in deforested areas for soil conservation or improvement and for erosion control, e.g. in Eritrea, Ethiopia and Kenya. It is also a useful shade tree, and is frequently planted as an ornamental tree and in windbreaks.
In traditional African medicine, an infusion of ground young twigs is taken against intestinal worms. People with rheumatism are treated by exposure to the smoke of burnt twigs and seed cones. The smoke is also inhaled as an expectorant. Ground dried leaves are applied on wounds of humans and animals. A hot bath to which the leaves are added is used in the treatment of fever. The resin is used as a stimulant and applied to ulcers. Bark macerations are drunk and applied as a vaginal wash as birth-control agents. A decoction of the seed cones is used as a sudorific and emmenagogue. In veterinary medicine, chopped and finely ground leaves mixed with water are used as a drench for horses and mules with stomach disorders, whereas a decoction of dry young branches is a medicine against itch of camels.
Juniperus procera has ceremonial and religious significance, as in some parts of Ethiopia, where it is used especially in September during the traditional orthodox ceremony of Meskel.
Production and international trade
There was formerly considerable overseas trade in African pencil cedar: in 1910, for instance, 31,000 logs were exported from East Africa to Germany. Later the wood of Juniperus procera was exported to Europe and North America in the form of slats for the production of pencils and other articles, but these exports have ceased. Cedar wood oil has also been exported.
The heartwood is pale red, yellow-brown or purple-red when freshly cut, turning reddish brown on exposure; it is well demarcated from the cream-coloured or white sapwood, which is up to 2.5 cm wide in mature trees. The grain is usually straight, texture fine and even. The wood is very fragrant, with a characteristic and persistent aromatic cedar smell. Ingrown bark, spiral grain and compression wood are common defects. The wood is liable to bleach in the sun and is sometimes streaked with zones of darker and lighter colour which produce an attractive figure.
The wood is medium-weight, with a density of 510–670 kg/m³ at 12% moisture content. It seasons well when dried with care, but larger pieces are liable to end-splitting and surface-checking, and the wood should not be allowed to dry rapidly in the initial stages. Kiln drying is preferable. The rates of shrinkage from green to 12% moisture content are 2.0% radial and 3.0% tangential, and from green to oven dry 3.3% radial and 5.0% tangential. Once seasoned, the wood is very stable; thus movement in service is small. At 12% moisture content, the modulus of rupture is 86 N/mm², modulus of elasticity 8925 N/mm², compression parallel to grain 38 N/mm², shear 10.3 N/mm² and Janka side hardness 1910 N.
The wood is easy to work with hand and machine tools, although it is rather brittle and fissile, tending to break and chip on drilling and mortising. It can split on nailing and screwing, and pre-boring is necessary. The wood glues, stains and polishes well.
The durability is high, also in the ground. The heartwood is resistant to fungi, termites and most borers except Oemida gahani. The sapwood is not susceptible to attack by Lyctus beetles. The heartwood is impermeable to preservatives, and only thin material can be sufficiently impregnated; the sapwood, however, is permeable.
The wood burns evenly when fresh, but fast, and the charcoal does not last long. The wood contains 0.5–3% essential oil, with as most important component cedrol (23–79%). Cedrol is known to have antitermite effects. Essential oil from the leaves has shown antioxidant activity. The leaves and bark contain diterpenes with antibacterial activity. The butanol fraction of an ethanol extract of the bark has shown anti-implantation activity in rats. The bark contains about 3.5% tannin.
Adulterations and substitutes
The properties of the wood of African pencil cedar are quite similar to those of ‘podo’ (Afrocarpus and Podocarpus spp.).
Large, evergreen, usually dioecious tree up to 40(–50) m tall; bole branchless for up to 20 m, straight, tapered, up to 200(–300) cm in diameter, often fluted; outer bark fissured, exfoliating in long narrow papery strips, pale brown weathering grey-brown; crown pyramidal in young trees, wide-spreading and flat-topped in older ones; branches spreading or ascending. Leaves decussately opposite, simple, scale-like, on ultimate branchlets triangular-rhombic, 0.5–1 mm × c. 0.5 mm, acute, on older branches lanceolate-acute and up to 6 mm long, margin entire, yellowish green to pale green. Male cone terminal on short branchlets, solitary, globose to ovoid, 2–5 mm × 1.5–3 mm, yellowish or green when young, orange-brown when mature; scales 10–12(–14), decussately opposite, peltate, each bearing (1–)2–3(–4) pollen sacs. Female cone terminal on short erect branchlets, mature one berry-like, globose, 3–7(–8.5) mm in diameter, brown, blue or purplish black, usually glaucous or pruinose, (1–)2–3(–6)-seeded; scales 4(–6), decussately opposite, fused. Seeds angular-ovoid, one side more or less flattened, 3.5–5.5 mm × 2–4 mm, yellowish brown.
Other botanical information
Juniperus comprises about 50 species and is very widespread in subtropical and temperate regions of the Northern Hemisphere, with some species in tropical mountains. Juniperus procera is the largest tree in the genus. Juniperus procera is closely related to Juniperus excelsa Bieb., distributed in Europe and temperate Asia. The 2 species have sometimes been treated as conspecific, but this view is not widely accepted.
Wood-anatomical description (IAWA softwood codes):
Growth rings: (40: growth ring boundaries distinct); (41: growth ring boundaries indistinct or absent); 43: transition from earlywood to latewood gradual. Tracheids: 44: tracheid pitting in radial walls (predominantly) uniseriate (earlywood only); 54: latewood tracheids thin-walled (double wall thickness less than radial lumen diameter); 56: torus present (pits in earlywood tracheids only). Axial parenchyma: 72: axial parenchyma present; 78: transverse end walls beaded or nodular. Ray composition: 80: ray tracheids absent or very rare; 85: end walls of ray parenchyma cells smooth (unpitted); 87: horizontal walls of ray parenchyma cells smooth (unpitted). Cross-field pitting: 93: cross-field pits cupressoid; 98: 1–3 pits per cross-field (earlywood only). Ray size: 102: average ray height very low (≤ 4 cells); 103: average ray height medium (5–15 cells); 107: ray width exclusively uniseriate.
(P. Baas & I. Heinz)
Growth and development
Growth of Juniperus procera is slow. In Ethiopia 10–15-year-old plantation trees were 6–9 m tall, with a bole diameter of 8–16 cm, whereas 30–40-year-old plantation trees were 17–21 m tall, with a bole diameter of 16–29 cm. In a 200-year-old stand, the trees were 37.5 m tall, with a bole diameter of 107 cm. In the Usambara mountains in Tanzania (altitude 1450 m, average annual temperature 18°C, average annual rainfall 1070 mm) 61-year-old Juniperus procera trees in a density of 182 trees/ha had an average height of 32.5 m and an average bole diameter of 47 cm. The standing volume was 247 m³ per ha. A naturally regenerated 15-year-old stand in Kenya, result of an earlier fire, had an average tree height of 14.7 m and an average bole diameter of 23 cm; 35 years later the trees in this stand (density 262 stems/ha) had an average height of 23.5 m and an average bole diameter of 39 cm. In a 41-year-old plantation in Burundi, trees had an average height of 24 m and an average bole diameter of 29.5 cm (range 19–50 cm).
Juniperus procera has irregular flowering and fruiting periods, only flowering once every several years. It is wind pollinated and seeds are dispersed by birds. Juniperus procera is assumed to be deep-rooting, like other Juniperus spp., but the characteristics of its root system are poorly known.
Juniperus procera is a highland species and prefers cold high ridges. It is commonly found between 1800 m and 2800 m altitude, but occurs in a broader range of 1000–3500 m, with an average annual temperature range from 5°C to 20°C. Average annual rainfall in the forest belt with much Juniperus procera is 1000–1400 mm, but the tree can grow in a wide range of rainfall zones (300–2000 mm/year). Individual trees can survive in hot and dry conditions, once established, but in areas with low rainfall, the trees are generally of poor form and small size. Where rainfall exceeds 1400 mm/year, the forests dominated by Juniperus procera are gradually replaced by moister types of evergreen forest in which Juniperus procera becomes increasingly rare. Juniperus procera prefers rocky soils, with a light to medium texture and free drainage.
Juniperus procera is a characteristic tree of the undifferentiated and dry Afromontane forest types, but can also occur in forests transitional between dry Afromontane forest and semi-evergreen bushland and thicket. The understorey of Juniperus procera forest is usually a dense, evergreen mix of shrubs and herbaceous plants. The trees are sometimes covered with mosses and lichens. Climbers are common (the large liana Toddalia asiatica (L.) Lam. is very frequent) and epiphytic figs are occasionally found. Juniperus procera is a prolific seed-bearer and the seeds, though sometimes damaged by seed-boring insects, are usually fertile. However, no regeneration is observed in mature juniper forests as young seedlings are very light demanding and absolutely intolerant of any decomposing organic matter covering the ground. Therefore the seeds can only germinate freely in open, grassed areas or among shrubs, such as in glades or forest edges, with adequate light and mineral soils. Consequently, Juniperus procera forests can only develop in two principal ways: either saplings are found growing under the shelter of bushes at forest edges, or natural regeneration occurs after a fire or in large clearings of other origin, giving rise to usually very dense, even-aged stands of trees with long, branch-free boles. Due to these strict requirements, artificial regeneration appears to be the easiest and fastest way to maintain Juniperus procera forests.
Propagation and planting
Juniperus procera is easily propagated by seed. The 1000-seed weight is 20–30 g. Seeds can be obtained by collecting seed cones from the tree, spreading them on a floor to dry, crushing them with mortar and pestle, and separating the seeds by sieving and winnowing. The seed stores well. The optimum temperature for germination is around 20°C; germination is better in light than in the dark. The germination rate in nurseries is usually 40% after 6 weeks, but considerable variation has been found in seed and germination characteristics of Juniperus procera. Germination can be enhanced by pre-treatment with hot water, concentrated sulphuric acid or scorching. Seedlings are ready to be planted out when 1–2 years old and 15–25 cm tall. Relatively dense spacing is required, preferably 1.2–2 m × 1.2–2 m, to promote self-pruning in the extremely branchy thicket-stage. Wildlings are also used for planting. Under conditions in which Juniperus procera readily regenerates, stand establishment by direct sowing may even be applicable.
Vegetative propagation of Juniperus procera is possible: stecklings (rooted cuttings) with well-developed root systems easily establish and grow well. In experiments, rooting was best in cuttings from young plants (5 months old), but somewhat older plants (10–15 months) yield more cuttings. Rooting in cuttings from mature trees is poor.
In plantations, weeding should be done during the rainy season at least once a year during the early growth stages. Pruning is an important management operation which can significantly increase the timber production of a stand, although the presence of wounds in which the heartwood is exposed increases the risk of damage by the wood-rot fungus Fomes juniperinus. Pruning should start 3–6 years after planting. Early selective thinning, starting in the 5th year, is also recommended to enhance crown development and diameter growth. Litter fallen from the tree makes the soil acidic, so Juniperus procera should not be intercropped with crops.
Diseases and pests
Juniperus procera is subject to serious attacks by the wood-rot fungus Fomes juniperinus. The fungus creates cavities of various sizes, and in the case of serious infestation a large tree may be reduced to a mere shell. Mature trees or trees growing in humid locations almost always contain at least some heart rot. The fungus cannot survive in dead trees. Measures to reduce damage by Fomes juniperinus include strict protection from fire and other injury, maintenance of dense stands to favour natural pruning while trees are still young (before heartwood formation), periodical thinning of all stems with broken branches or wounds in which the heartwood is exposed, and removal of stems already attacked by the fungus. The tree is also affected by Rhynchosphaeria cupressi, causing stem and branch canker.
Juniperus procera is damaged by the cypress aphid (Cinara cupressi), but not as severely as Cupressus lusitanica Mill.
The production of suitable logs for the sawn wood and veneer market may be possible with a rotation period of 70–100 years.
The growth of plantations ranges from 3.5 to 13 m³/ha/year, averaging 7.5 m³/ha/year, considerably less than that of some exotic species on the same sites, e.g. 50 m³/ha/year for Eucalyptus globulus Labill.
In spite of its wide distribution, Juniperus procera is mentioned in the 2006 IUCN Red list of threatened species, although in the lower risk category. Overexploitation, changing land use patterns, browsing (particularly by buffalo and elephants) and the increasing populations of fast-growing exotic species are contributing to the decline of Juniperus procera. Populations in Ethiopia and Kenya are of wide extent, but outlying populations in Zimbabwe, DR Congo and Malawi are extremely small and threatened. The single wild Juniperus procera tree specimen known in Zimbabwe is protected.
Juniperus procera has favourable attributes for employment as a plantation species: it is able to adapt to extreme climatic conditions and it produces high-quality timber. However, its slow growth, coupled with fluting of the bole and poor survival in the field due to attacks by heart rot, has discouraged cultivation in its native range. Replanting to convert poor sites into woodland is carried out in deforested areas, e.g. in Eritrea, Ethiopia and Kenya. However, this practice is limited, mainly because it does not provide direct income to the countries concerned. In general it is likely that in plantation forestry continued preference will be given to species that grow faster than Juniperus procera.
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Sources of illustration
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Correct citation of this article:
Couralet, C. & Bakamwesiga, H., 2007. Juniperus procera Hochst. ex Endl. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, tree habit; 2, branchlet with male cones; 3, branchlet with female cones; 4, seed cone; 5, seed.
Redrawn and adapted by Iskak Syamsudin
habit of free-standing tree
Juniperus landscape, Ethiopia
base of bole
bole and crown
branch with female cones
transverse section of bole