The Pinus kesiya complex is widely distributed between 30oN and 12oN in South East Asia. It occurs in Burma, India, Tibet, Laos, Vietnam, Thailand, the Philippines and the Peoples Republic of China. It has a disjunct distribution pattern suggesting a high degree of ecotypic variation. The taxonomic relationships between several three needled pines occurring in South East Asia (including P. kesiya and P. yunnanensis) are unsettled (Armitage and Burley 1980). Although there is good botanical and biochemical evidence of regarding the complex as elements of a single species, P. kesiya, the species (notably P. kesiya and P. yunnanensis) will be referred to as separate species in this context in order to minimise confusion.
Pinus kesiya is an important conifer species for plantation programmes in the tropical zone. It grows best at medium to high rainfall and at medium altitudes (600-1800 m.a.s.l.). At lower altitudes it is superseded by Pinus caribaea/oocarpa and at higher altitudes it gives way for various sub-tropical pines, which are less frost sensitive, e.g. Pinus patula (Armitage and Burley 1980) . It is fast growing, has the capacity to adapt to various growing conditions (high plasticity), is long living and produces a high quality, long-fibered pulp.
Poor stem form and branching characteristics have militated against the acceptance of P. kesiya as a plantation species (Armitage and Burley 1980). Stem defects as basal sweep, butt sweep, sinuosity, crookedness, nodal swelling, multiple stems commonly occur, as do whorls of heavy persistent branches and long internodes (Burley and Wood 1976). Like other fast growing tropical and sub-tropical pines it has a large juvenile core with less desirable characteristics such as lower density and tracheid length. On favorable sites overspeeded growth may result in total tree collapse (flops) (Armitage and Burley 1980). In addition, the species is sensitive to even the slightest reduction of access to light.