Tikovina

Teak is a large, deciduous tree that occurs in mixed hardwood forests. It is native to south and southeast Asia, mainly Bangladesh, India, Indonesia, Malaysia, Myanmar, Thailand and Sri Lanka. Myanmar's teak forests account for nearly half of the world's naturally occurring teak. The tree grows up to 40 m tall and has grey to greyish-brown branches. Its fragrant white flowers are borne on panicles from June to August. Teak is naturalised and cultivated in many countries in Africa and the Caribbean. Molecular studies show two centres of genetic origin, one in India and the other in Myanmar and Laos. It grows in habitats ranging from arid areas with 500 mm of rain a year to very moist forests with up to 5,000 mm. Its IUCN conservation status is Endangered.

The Wood

The heartwood is yellowish to golden-brown. The sapwood is whitish to pale yellowish brown. Teak darkens as it ages, and there can be a large variation depending on which region the teak is from. The wood is hard and its rings are porous; old growth has much tighter rings than new growth. In the wood, the number of black stripes increases with age, and these stripes are a defense that protects it from insects and fungi. Teak's natural oils make the timber termite- and pest-resistant. It is also highly resistant to rot, fungi and mildew. Teak is durable even when not treated with oil or varnish. The wood has a relatively low shrinkage ratio, which suits uses where it undergoes periodic changes in moisture. Teak is both an excellent structural timber and easy to work and finish. Left unfinished, it weathers to a silver grey, while oiling with linseed or tung oil gives a somewhat dull finish.

Chemistry

The anthraquinone 2-methylanthraquinone (C₁₅H₁₀O₂) is found in teak heartwood and is often associated with its high durability. Reports indicate that teak wood extractives contain 0.3%-0.9% of this compound. In no-choice feeding tests on a subterranean termite, the amount of 2-methylanthraquinone in the extractives was not related to feeding deterrence or toxicity. Teak wood extractives are fundamental to its resistance against termites and fungi. 2-Methylanthraquinone has a molecular weight of 222.24 and the IUPAC name 2-methylanthracene-9,10-dione.

Uses

Teak wood is used for boat building, exterior construction, veneer, furniture, carving, turnings and various small projects. It is particularly valued for its durability and water resistance. Much of the world's teak is exported by Indonesia and Myanmar. Teak's high oil content, high tensile strength and tight grain make it particularly suitable where weather resistance is desired. The leaves are used in gudeg, a dish of young jackfruit from Central Java, and give it its dark brown colour. The LNER used teak for its coaches until 1942.

Cultivation

Teak plantations were widely established in Equatorial Africa during the colonial era, and a plantation-grown market is growing in Central America and South America. Propagation by tissue culture for plantation purposes is commercially viable. The teak defoliator, a moth native to southeast Asia, is a pest whose caterpillar feeds on teak.