Pinus finlaysoniana Wall. ex Blume

A large tree up to 50(-70) m tall with a straight and cylindrical bole free of branches for 15-25 m and an average diameter of 55 cm, but occasionally up to 140 cm, thick bark which forms plates and is grey-brown underneath, but scaly and more reddish tinged upwards, and heavy horizontal or ascending branches. Needles in pairs, slender but rigid, 16-25 cm long, with persistent basal sheaths. Cones solitary or in pairs, almost sessile, cylindrical, 5-11 cm long, after opening twice as thick and ovoid, generally falling off soon; apophysis broadly tetragonal with a smooth, almost depressed umbo. Seed small with a deciduous wing of c. 2.5 cm long. The normal architecture of pines is Rauh's model. The trunk is monopodial and grows rhythmically, and develops tiers of branches; the formation of cones does not affect shoot construction. Sometimes ""foxtails"" occur, plants without branching and without growth rings in the wood. Merkus pines of the Asian mainland and the Philippines differ slightly from those of Sumatra: the seedlings have a ""grass stage"", the needles are slightly longer, the cones are less cylindrical, and the seeds nearly twice as heavy. In Sumatra three different strains of P. merkusii have been recognized (the Aceh, Tapanuli and Kerinci strains) which differ markedly in e.g. stem form, branching, bark, resin content and susceptibility to attack by the moth Milionia basalis.

In plantations, trees of P. merkusii reach sexual maturity when about 20 years old. They bear cones every year, although seed production varies. In Sumatra ripe seeds are produced most abundantly between July and November, but viable seeds are produced throughout the year.

It is the southernmost occurring pine of all pines, and the only one whose natural distribution extends into the southern hemishpere. The naturally occurring pines of South-East Asia (P. kesiya and P. merkusii) inhabit a wide range of forest and savanna habitats. They are pioneers and their natural range is extended by colonization following disturbances such as fire. They grow, for instance, scattered in fire-prone grassland and woodland. The trees are increasing in number in recently disturbed areas. They are strongly light-demanding and habitually grow in pure stands. Pines grow naturally in South-East Asia only in strongly seasonal environments.

Eastern Burma, Indo-China, southern China, northern Thailand, the Philippines (Mindoro, western Luzon), Sumatra (Aceh, Tapanuli, Kerintji mountain); commonly planted in South-East Asia.

Successful natural regeneration is only possible where a relatively large amount of sunlight reaches the ground. In Sumatra ripe seeds are produced most abundantly between July and November, but viable seeds are produced throughout the year. Only cones that have just changed their colour from green to brown should be collected and air dried. Seeds germinate in 8-12(-21) days, and need no pretreatment. However, they are often soaked in cold water overnight before sowing. A germination rate of P. merkusii seeds of 40-60% may be expected. After about 8 months the seedlings of P. merkusii in nursery beds are 20-25 cm tall and ready for planting into the field. Propagation by tissue culture is possible. Suspensor, root tissue and hypocotyl segments of 2-week-old seedlings of P. merkusii have been used, and they all readily yield callus when cultured on a Murashige and Skoog mineral formulation supplemented with naphthalene acetic acid (0.25-0.65 ppm) and benzylamino purine (1.0-2.0 ppm).

Husbandry: In plantations of P. merkusii the first thinning is usually carried out in the 9th or 10th year, and about every 5 years thereafter. Rotation cycles of 30 years are needed for optimal timber production and have been stipulated by the Indonesian forestry administration. For the production of pulpwood, a cutting cycle of 15 years is usually practised. Mycorrhizae are required for successful growth and allow seedlings to survive in more adverse sites. P. merkusii and P. kesiya require more weeding than P. caribaea and P. oocarpa. The prolonged ""grass stage"" often present in young trees of P. merkusii means increased weeding requirements when compared to P. caribaea, P. oocarpa and P. kesiya.

The seeds can be stored for several years, provided they are kept dry, cold and in an airtight container. However, seeds of P. merkusii are reported to have a rather short viability; seeds from Sumatra can be stored dry for only 1-2 years, and those from continental Asia during even shorter periods. The weight of 1000 seeds of Sumatran P. merkusii about 17 g, and of continental provenances of P. merkusii 25-33 g.

Intercropping: In Indonesia P. merkusii has been successfully intercropped with Irish potatoes. Shade or shelter: The tree is used to shade out alang-alang grass with fairly good results.

Gum or resin: Good quality oleoresin is collected from this species, often on plantation scale. Timber: Merkus pine is a general-purpose timber; it can also be used for construction work, flooring and boat building as it is fairly durable and heavy.