It is shown that the planting site has a strong effect on the growth, development and wood quality of teak plantations. The productivity of a plantation can be largely improved through the selection of a correct site for the plantation programme. It is noted that the teak distribution pattern in its natural range is of discontinuous or patchy type (Troup, 1921; FAO, 1956,1958). Size, quality, density, and the form of teak trees varies from one location to another. There are several factors which control the distribution and growth pattern of the species. The major factors include the amount and distribution of rainfall and moisture, soil and light.
It is common knowledge among Thai-loggers that teak from wetter site conditions, e.g. along river banks or in the lower moist teak forest, is usually darker in wood colour than that from drier site conditions. Teak wood colour seems to be influenced by the site. As the golden brown wood colour is one of teak's most attractive timber qualities, the variation in wood colour and texture has been widely studied (Sono and Saensakul, 1959; Sandermann and Simatupang, 1966; Sunyata et al., 1992; Kaosa-ard, 1993). A study on clonal variation in wood colour and texture in Thailand in a 20-year old clonal test clearly demonstrated that teak wood colour and texture is strongly controlled by the planting site (Kaosa-ard, unpublished data). In this test, clones of trees from different locations with different wood colours (i.e. dark brown, golden brown, light brown colours, and wood textures, i.e. stony-wood and waxy-wood textures (produced similar wood colour and texture when planted on the same site (< 0.5 ha plot). Similarly, results of 14-year old intentional provenance trials in Thailand (established within and outside the teak bearing area) clearly showed that there is no or little significant effect of provenance or seed source on wood colour (i.e., the golden brown colour) and wood density (Kaosa-ard, 1993). These trials consist of provenances from India, Thailand, Indonesia, Lao and African races. Within a provenance, there is a marked site effect on wood colour, e.g. golden brown colour (Kaosa-ard, 1993). The proportion of trees with golden brown wood colour decreases from a natural teak bearing site (Ngao, Lampang) to a non-teak bearing site (Khon Kaen), i.e., from 74% to 63% (Kaosa-ard, 1993). The cause of such variation is still not known but is possibly due to differences in soil chemistry and moisture content in the two planting sites. (Credit : Dr. Apichart Kaosa-ard)