Pinus recurvata Rowlee

Pinus caribaea is a fine tree to 20-30 m tall, often 35 m, with a diameter of 50-80 cm and occasionally up to 1 m; trunk generally straight and well formed; lower branches large, horizontal and drooping; upper branches often ascending to form an open, rounded to pyramidal crown; young trees with a dense, pyramidal crown. Leaves needlelike, crowded and spreading at ends of twigs, remaining attached for 2 years, in fascicles of 3-5, mostly 15-25 cm long, 1.5 mm broad or less, rigid serrulate, dark or yellowish-green, slightly shiny, with stomata in whitish lines on all surfaces. Strobili appear before the new leaves; male strobili many and sessile in whorled, short, crowded clusters near ends of twigs, mostly in lower part of the crown; mature cones usually reflexed, symmetrical; cone scales reflexed or wide spreading, thin, flat, dark chocolate-brown on inner surfaces; seeds narrowly ovoid, about twice as long as broad, pointed at both ends, 3 angled, averaging less than 6 mm long, 3 mm wide, black, mottled grey or light brown. ‘Pinus’ is from the Greek word ‘pinos’ (pine tree), possibly from the Celtic term ‘pin’ or ‘pyn’ (mountain or rock), referring to the habitat of the pine.

Young plantations usually start bearing female cones when they are 3-4 years old but these do not produce fertile seed owing to the inadequate supply of pollen at this age, unless older plantations adjoin the site. Male and female flowers are borne on the same plant. The female cones are the equivalent of long shoots whereas the male cones are the equivalent of needle bundles (short shoots). There is a variation in the proportion of male to female cones, with some trees producing almost entirely male cones and others almost entirely female cones.

Soils are usually loams or sandy loams, sometimes with high amounts of gravel and generally well drained. The pH is usually between 5.0 and 5.5.

This species grows best in frost-free areas up to about 700 m in more fertile sites with good subsoil drainage and annual rainfall of 2000-3000 mm. Generally at elevations of 600-800 m it is associated with P. oocarpa var. hondurensis and P. oocarpa var. ochoterenai. P. caribaea is rated as moderately fire resistant. It tolerates salt winds and hence may be planted near the coast.

The 1st seed exports of P. caribaea were from British Honduras to Placerville in California and to South Africa. Around 1930, a plot of P. caribaea was planted at Imbil in Queensland, Australia. Few countries initiated trials of P. caribaea after these initial introductions until the British Honduras itself started plantations of the local variety (var. hondurensis) from 1943 onwards. Cuba established several acres of its variety starting in 1945. In 1946, seeds and soil from the coastal pine zone in British Honduras were sent to Trinidad, and trial plots established in 1948. The 1st plots in Malaysia were planted in 1953. East and central African countries began trials from 1957. An FAO seminar on tropical pines in Mexico in 1960 stimulated an upsurge of replicated provenance trials in Fiji, Kenya, Malawi, Queensland, Sudan, Tanzania, Uganda, South Africa and Zambia. The list of countries grew rapidly to include Colombia, Costa Rica, Gambia, India, Jamaica, Madagascar, Nigeria, Sierra Leone, Sri Lanka and USA.

Collection of cones can start as soon as they begin to change from green to brown on the tree; collecting cones earlier that this may give seeds with short viability. Seeds can be extracted from cones opened in the sun by raking them over as they lie open on the tarpaulin. P. caribaea is propagated artificially from seed. Seeds germinate in 8-12 (max. 21) days, and need no pretreatment. However, they are often soaked in cold water overnight, followed by 2-3 days of cold storage at 4-5 deg. C. Mechanical sifting of seed before sowing to eliminate hollow and defective seed can also improve germination considerably and make it possible to sow single seeds directly into containers instead of 1st sowing in germination beds. Seed of good quality germinate within 8-21 days of sowing.

Initial spacing for P. caribaea depends on the markets for which the pine is being grown and the technique used in tending the plantation. Mechanical cultivation requires a spacing of at least 3 m between rows, but close spacing is possible within rows. When it is grown for pulpwood, a spacing of 2 x 2 m is used to give maximum stem production of suitable sizes in the shortest time possible without thinning. Pruning is recommended to reduce fire danger, improve form, improve access within the crop, and reduce the size and frequency of knots, especially in saw logs. In P. caribaea plantations grown for pulpwood on a short rotation of 10-15 years, there may be 1 early cleaning thinning at 3-4 years old to remove malformed trees, or no thinning at all. Where both saw logs and pulpwood are being produced, a heavy thinning at 10 years for pulpwood may leave an open crop for logs saw harvested during the 2nd thinning at 17 years. The tree responds well to low levels of nitrogen fertilization, but trials in the Philippines showed no response to either phosphorus or potassium.

One of the most important insect pests is a bark beetle, the southern pine beetle (Dendroctonus frontalis), found in the southern USA and Central America. A related species is D. mexicana, whose outbreak caused damage to several hectares of P. caribaea var. hondurensis in Honduras. Other bark beetles include Ips calligraphus, which is widely distributed in Canada and Central America to West Indies. Aphids such as the pine aphid (Pineus laevis) and Cinara carolina (North American aphid), leaf cutting insects such as Atta spp., and termites also attack the tree. P. caribaea diseases are the nursery diseases, which include ‘damping off’ and seedling blight, and plantation diseases such as foliage blight, stem rot, stem die-back, cone rust, sap stain, heart rot and root rot.

Seed storage behaviour is orthodox; viability is lost within 1 year in hermetic storage with seeds at room temperature with 13 ± 2% mc; no loss in viability during 2 years hermetic storage at room temperature; no loss in viability after 5 years of storage at 0-5 deg. C with over 8% mc; hermetic storage at 4.5% mc recommended; about 16% viability lost after 2.7 years of hermetic storage at 8 deg. C. There are 59 000-72 000 seeds/kg, depending on the variety.

Erosion control: In many places where P. caribaea grows, the mat of needles on the ground is considered valuable for the protection of the soil surface from erosion. Reclamation: In Sri Lanka a massive reforestation programme was undertaken with plantations of P. caribaea to convert heavily eroded lands on which nothing else could be grown. It is the only species so far successfully used to clothe barren eroded and denuded lands with a tree cover.

Fuel: P. caribaea, being a fast-growing species, can be used for fuelwood for both industrial and home use. However, it throws out sparks when burning. Fibre: The presence of long tracheids makes P. caribaea (and other pines) a good source of wood pulp. Plantations at 15 years are ideal for pulpwood production. The tree is used in Nicaragua and Honduras for general-purpose pulpwood. Wood pulp is also used for the manufacture of particleboard, fibreboard and chipboard. Timber: Plantation-grown wood has an average density of 410 kg/m³. The grain is even to finely interlocked with a coarse texture. Transmission poles of P. caribaea are popular in Tanzania and Malaysia, among other places. Its low timber density and other poor properties, however, render the timber unstable for structural work or even furniture. The wood exudes much resin, which makes it less suitable for certain uses such as joinery and flooring. It can be used for shuttering, temporary applications and packaging. Ease of setting, ease of nailing it, and its resistance to splitting render it useful for turnery, toys, moulding and other novelty items. Gum or resin: P. caribaea can be effectively tapped for oleoresins from when it is 10 years old and has a 20 cm dbh. In Sri Lanka, an industry has been established to manufacture gum resin, turpentine and heavy oils from oleoresins. An average of 25 g per tree per day of oleoresins can be tapped. About 75% gum resin and 20% turpentine can be manufactured from the oleoresin. Tannin or dyestuff: P. caribaea bark contains tannin; about 10% can be extracted and dried to a reddish powder soluble in water. Medicine: P. caribaea leaf oil is sometimes used for medicinal baths; locally, the seeds may be consumed.