Pinus caribaea (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
|Essential oil / exudate|
Pinus caribaea Morelet
- Protologue: Rev. Hort. Côte d’Or 1: 107 (1851).
- Family: Pinaceae
- Chromosome number: 2n = 24
- Caribbean pine, pitch pine, Caribbean pitch pine, Nicaragua pine, Cuban pine, Honduras pine, yellow pine (En).
- Pin mâte, pin jaune, pin caraïbe, pin des Caraïbes, pin de Cuba (Fr).
- Msindano (Sw).
Origin and geographic distribution
Pinus caribaea occurs naturally in eastern Central America, Cuba and the Bahama Islands. It is planted throughout the tropics, including many countries of tropical Africa, and in Australia and New Zealand.
The wood (trade names: Caribbean pitch pine, Honduran yellow pine) has a comparatively low density and exudes much resin, making it less suitable for e.g. joinery and flooring, and limiting its value as a timber. Nevertheless, it is used for a wide range of purposes, including construction, light flooring, joinery, inexpensive furniture, boxes, pallets, turnery, toys and, after treatment with preservatives, poles, posts, railway sleepers and mine props. Resin-soaked wood is popular for boat decking, because of its high durability. The wood is also suitable for interior trim, veneer, plywood, piles, vats, particle board and fibre board. It is used as fuelwood, although it tends to throw out sparks, and for the production of charcoal. The wood is also used for the manufacture of paper, but is not suitable for dissolving-grade pulp.
When tapped, the tree yields a good quality of oleoresin which is distilled to give turpentine and rosin. Turpentine is used in paint and batik industries, and rosin is used in the production of paper, soap and glue. The oleoresin products are often termed ‘naval stores’ because of their historic use for ship caulking. Pinus caribaea is planted in windbreaks and as an ornamental and shade tree. The mat of needles on the ground is considered valuable for protection against soil erosion. The seeds are locally consumed.
Production and international trade
Pinus caribaea is fairly important for the production of timber, but trade and export statistics are unavailable because the wood is often used locally. The pulp is often mixed with that of other species.
The heartwood is yellowish to reddish brown and distinctly demarcated from the white or yellowish sapwood. The grain is straight, texture medium to coarse. Growth rings are distinct. Numerous resin canals are present and clearly visible as straight brown streaks on longitudinal surfaces.
Wood properties show large differences between sites and between trees. The wood is moderately lightweight to fairly heavy, with a density of 350–560(–820) kg/m³ at 12% moisture content. The wood from slower-growing trees from natural stands has a higher density and lower resin content than the wood from faster-growing trees from plantations. The wood air dries well, but end splits may occur. Boards of 30 mm thick require about 6 weeks to air dry from green to 20% moisture content. Conventional kiln drying is successful for both 25 mm thick material (which takes 3–4 days to dry to 12–14% moisture content) and 50 mm thick material. High temperature drying has proved successful for framing sizes. Boards of 30 mm thick of plantation-grown wood may be dried in a solar kiln to 12% moisture content in 40 days. Rates of shrinkage from green to oven dry are 1.9–4.5(–6.3)% radial and 5.7–7.9% tangential.
At 12% moisture content, the modulus of rupture is (50–)61–115 N/mm², modulus of elasticity (2600–)6300–15,400 N/mm², compression parallel to grain (22–)34–59 N/mm², shear 14 N/mm², cleavage 12 N/mm radial and 13 N/mm tangential, Janka side hardness 3020–5520 N and Janka end hardness 3740 N.
The wood works and finishes well with hand and machine tools, although resin may clog and gum up tool edges and surfaces. It takes nails and screws particularly well and glues satisfactorily.
The wood is moderately durable, being susceptible to marine borer and termite attacks, but resistant to powder-post beetles and fungi. Resistance to insect attacks increases with increasing resin content. The heartwood is moderately resistant to impregnation with preservatives; the sapwood is highly permeable and easily treated in open-tank or pressure-vacuum systems. The energy value of the wood is 20,300 kJ/kg.
The wood fibres are on average 4.6 mm long and 41–52 μm wide. The wood fibres of 8–12-year-old trees from Tanzania were 2.9–3.0 mm long, with a diameter of 40–47 μm and a cell wall thickness of 4.2–4.5 μm. The chemical composition of the oven-dry wood was: holocellulose 64–65%, α-cellulose 40–42% and lignin 31%. The solubility in cold water was 1.8–2.6%, in hot water 2.1–3.3%, in alcohol-benzene 1.2–1.3% and in 1% NaOH 11. 6–12.8%. Pulping with the sulphate (kraft) process yielded 41–46% screened pulp, with a kappa number of 23–48, satisfactory tensile and bursting strengths, but relatively low tearing strength.
The oleoresin, which is found in the intercellular canals in especially the sapwood, is a pale yellow, clear and sticky mass, becoming brittle on evaporation. It is a hydrophobic substance soluble in neutral, non-polar organic solvents such as dry ethyl ether, hexane, and other petroleum solvents. On distillation, it produces gum rosin and gum turpentine in a ratio of 4–6:1. Gum rosin is a brittle solid, insoluble in water, but soluble in many organic solvents. It consists primarily of a mixture of abietic and pimaric-type acids. Gum turpentine is a liquid mixture of mainly terpene hydrocarbons and terpenoids, including (+)-α-pinene, (–)-α-pinene and (–)β-phellandrene. From the bark about 10% tannin can be extracted; it can be dried to a reddish powder soluble in water. Hexane extracts of the bark have shown strong antifungal and antibacterial activity, and may have potential for control of fungi and bacteria in the pulp and paper industry.
- Evergreen, monoecious, medium-sized tree up to 30(–45) m tall, but in plantations usually much smaller; bole branchless for up to 21 m, up to 80(–135) cm in diameter, usually straight, cylindrical; bark surface reddish brown to pale brownish grey, deeply fissured, inner bark very resinous; crown thin, rounded to pyramidal, slightly spreading; twigs orange brown, later turning grey-brown.
- Leaves in bundles of (2–)3(–5) in whorls at the end of the shoots, needle-shaped, 15–25 cm long, minutely toothed, stiff, dark or yellowish green, slightly shiny.
- Male cone in dense clusters, 2–4 cm × 0.5 cm, red-brown.
- Mature female cone solitary or in groups of 2–5, on a peduncle 1–2 cm long, ovoid, 4–14 cm × 2.5–4 cm, reddish brown, with reflexed or wide spreading scales.
- Seeds narrowly ovoid, up to 6 mm × 3 mm, with a persistent membranous wing up to 20 mm long, black to mottled grey or pale brown.
- Seedling with hypogeal germination.
Other botanical information
Pinus is a large genus comprising over 110 species, almost all restricted to the northern hemisphere. Many Pinus species are cultivated outside their natural distribution area, in tropical, subtropical and temperate regions. In the tropics 2 species are more important than all others: Pinus caribaea in the lowland humid tropics and Pinus patula Schltdl. & Cham. in the cooler highland tropics and subtropics.
Pinus caribaea is often divided into 3 varieties: var. bahamensis (Griseb.) W.H.G.Barrett & Golfari, var. caribaea and var. hondurensis (Sénécl.) W.H.G.Barrett & Golfari. In plantations outside the native area of the species var. hondurensis is generally grown; it is the most suitable variety for tropical lowlands. In South Africa it is recorded to have more crooked stems than the other 2 varieties. Var. bahamensis is reported to have some tolerance to shoot moth attack. Pinus caribaea var. hondurensis forms natural hybrids with Pinus oocarpa Schiede ex Schltdl. Pinus caribaea has often been mistaken for Pinus elliottii Engelm. in the past.
Wood-anatomical description (IAWA softwood codes):
- Growth rings: 40: growth ring boundaries distinct; (42: transition from earlywood to latewood abrupt); (43: transition from earlywood to latewood gradual).
- Tracheids: (44: tracheid pitting in radial walls (predominantly) uniseriate (earlywood only)); (45: tracheid pitting in radial walls (predominantly) ≥ 2-seriate (earlywood only)); 46: tracheid pits in radial walls oppositely arranged (earlywood only); 55: latewood tracheids thick-walled (double wall thickness larger than radial lumen diameter); 56: torus present (pits in earlywood tracheids only).
- Ray composition: 79: ray tracheids commonly present; 82: cell walls of ray tracheids dentate; 83: cell walls of ray tracheids reticulate; 85: end walls of ray parenchyma cells smooth (unpitted); 87: horizontal walls of ray parenchyma cells smooth (unpitted).
- Cross-field pitting: 91: cross-field pits pinoid; 98: 1–3 pits per cross-field (earlywood only).
- Ray size: 103: average ray height medium (5–15 cells); 107: ray width exclusively uniseriate.
- Intercellular canals: 109: axial intercellular (resin) canals present; 110: radial intercellular (resin) canals present; 117: epithelial cells thin-walled.
Growth and development
Pinus caribaea usually grows rapidly. In Nigeria 6-year-old trees were 7–8.5 m tall, and 11-year-old trees 17 m. In trials in Rwanda 13-year-old trees were 17 m tall, with a bole diameter of 18.7 cm. In Malawi 9-year-old trees (density 670 trees/ha) were on average 19 m tall. In South Africa (70 m altitude, mean annual temperature 22°C, mean annual rainfall 965 mm) 34-year-old trees reached a height of 27 m and a bole diameter of 47 cm. Bole straightness generally improves from the subtropics towards the tropics. Fairly often ‘foxtails’ occur, plants without branching and without growth rings in the wood. Foxtailing is a reaction to off site planting.
In southern Africa female flowering starts when trees are 3–4 years old, but male flowering starts later. Pollination is by wind. The time between pollination and ripening of the female cones is 18–21 months. Cones are readily shed from the branches, but sometimes persistent for over one year. Seed dispersal is by wind, but sometimes birds, rodents and people, who gather the seeds for food, also disperse them. Outside its native area Pinus caribaea rarely regenerates naturally.
Pinus caribaea is mostly grown up to 1000(–1500) m altitude, in areas with a mean annual temperature of 20–27°C, a mean maximum temperature of the warmest month of 28–34°C, a mean minimum temperature of the coldest month of 8–23°C, an average annual rainfall of (650–)1000–3000(–4000) mm, and a dry season of up to 6 months. It is moderately drought resistant, but does not tolerate frost. The tree is moderately tolerant to wind, also to salt wind, and it may be planted near the coast. Pinus caribaea grows on a wide variety of soils, but does best on well-drained, deep, fertile soils with pH 5–5.5. It tolerates seasonally waterlogged soils. Young trees are highly susceptible to fire damage, but older trees are moderately fire resistant. Pinus caribaea is strongly light-demanding.
Propagation and planting
Pinus caribaea is easily propagated from seed. The 1000-seed weight is 12–33 g. To obtain seed, cones can be collected as soon as they begin to change from green to brown on the tree; cones collected earlier may give seeds with short viability. Seeds are collected after sun-drying the cones in the sun or in open-sided sheds covered with plastic roofs. Seeds can be stored for up to 10 years under dry (below 10% humidity), cold (0–10°C) and airtight conditions. Pre-treatment before sowing is unnecessary, but soaking in water for 12–48 hours gives more uniform germination. Germination takes 8–21(–42) days, and up to 80% germination is common. Mycorrhizae are necessary for seedling growth, so it is recommended to inoculate with spores or to add soil from near established trees. Seedlings are suitable for planting out after 4–8 months, when they are 20–30 cm tall. The planting site should be thoroughly cleaned. Initial spacings are 2–5 m × 2–5 m, depending on production aims, with pulpwood plantations having the closest spacing. For resin production the recommended spacing is 4 m × 4 m. Direct sowing is uncommon. Vegetative propagation is possible using stem cuttings, grafting, air-layering or tissue culture.
Weeding is recommended during the early years, also to decrease the risk of fire. Pruning is recommended to reduce the risk of fire, improve access, improve tree form and reduce the size and frequency of knots. In plantations for sawn wood, veneer and large posts, trees are planted at an initial density of 1100 trees/ha, pruned during the first years, and later thinned to a final density of 250–400 trees/ha, with rotations of 15–25 years. In pulpwood plantations there may be a single thinning at 3–4 years to remove malformed trees or no thinning at all. Where both timber and pulpwood are produced, plantations can be heavily thinned when 10 years old to obtain pulpwood, with a more open plantation remaining for the production of timber.
Diseases and pests
Needle blight caused by Cercospora pini-densiflorae can seriously attack plantations. Damage by Armillaria mellea has been recorded in Tanzania, Malawi and Mauritius. In nurseries damping off may occur. Pinus caribaea is resistant to pitch canker (Fusarium circinatum), a serious disease threatening pine plantations in South Africa.
To obtain the resin various methods are practised. The first tapping or wounding of a living tree, at 30–40 cm above the ground, is about 1.3 cm wide and 30 cm long and is followed by a series of tappings until breast height is reached. A sulphuric acid solution (usually 40–60%) is applied immediately after tapping. This process yields the ‘gum naval stores’ which is the major source of the world’s supply of rosin and turpentine. ‘Wood naval stores’ can be obtained by solvent extraction of stumps of old trees; the resin obtained in this manner is less pure. Turpentine and wood resin can also be obtained as byproducts from the kraft or sulphate pulping of pines. Turpentine is removed from the chip digester during the initial steaming and is condensed from the relief gases. This method gives ‘kraft naval stores’.
Mean annual volume increments are 10–40 m³/ha. In Malawi 9-year-old trees (density 670 trees/ha) yielded 179 m³/ha. Because branching is light, the yield of first-grade structural timber is exceptionally high.
Handling after harvest
Freshly felled logs exude copious amounts of resin. Although not numerous, knots can cause degrade because they are large and tend to cause splitting on drying.
Felled logs discolour easily and should be converted and dried rapidly to avoid blue stain. Seasoned boards should be stored under cover.
Genetic linkage maps of Pinus caribaea var. hondurensis have been made using AFLP and microsatellite markers.
Provenance trials have been conducted in over 50 countries, including Gambia, Sierra Leone, Côte d’Ivoire, Nigeria, Congo, Sudan, Kenya, Uganda, Tanzania, Malawi, Zambia, Zimbabwe, South Africa and Madagascar, with var. hondurensis consistently showing the fastest growth. Clonal material of about 150 ‘plus trees’ has been distributed by the Oxford Forestry Institute, and clone banks were established in Zimbabwe, Australia and Brazil. A hybrid of Pinus caribaea var. hondurensis and Pinus elliottii has become important in plantations in Queensland (Australia) because of its superior growth and shape.
Pinus caribaea is commonly planted in the tropics because of its fast growth, ability to grow on virtually all soil types, the detailed information available on its silviculture, and the suitability of the wood for a wide range of applications. It has become the most important pine of the lowland humid tropics. However, the quality of the wood is often not high because of the high resin content, and improvement of the wood quality should be a research priority.
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Sources of illustration
- Farjon, A., 1984. Pines: drawings and descriptions of the genus Pinus. E.J. Brill, Leiden, Netherlands. 220 pp.
- A.A. Oteng-Amoako, Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
- M. Brink, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Correct citation of this article
Oteng-Amoako, A.A. & Brink, M., 2008. Pinus caribaea Morelet. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 9 July 2021.
- See the Prota4U database.