teak

Teak
Teak foliage and seeds
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Lamiales
Family:	Lamiaceae
Genus:	Tectona
Species:	T. grandis
Binomial name
Tectona grandis L.f.

Flowers at Ananthagiri Hills, in Rangareddy district of Andhra Pradesh, India.

Flower, fruit & leaves of Tectona grandis in Kolkata, West Bengal, India.

U Bein Bridge Amarapura, Myanmar. The longest teak bridge in the world at 1.2 km (0.75 mi) in length.

Teak is the common name for the tropical hardwood tree species Tectona grandis and its wood products.^[1] Tectona grandis is native to south and southeast Asia, mainly India, Indonesia, Malaysia, and Burma, but is naturalized and cultivated in many countries, including those in Africa and the Caribbean. Burma accounts for nearly one third of the world's total teak production.^{[citation needed]}

The word teak comes from the Tamil (in the Dravidan region) word thekku.^[2] This tree is mentioned in the seventh-century literature of Tamil popularly known as the Tevaram.

Tectona grandis is a large, deciduous tree that is dominant in mixed hardwood forests. It has small, fragrant white flowers and papery leaves that are often hairy on the lower surface.

Description

Tectona grandis is a large, deciduous tree up to 40 m (131 ft) tall with gray to grayish brown branchlets. Leaves are ovate-elliptic to ovate, 15–45 cm (5.9–17.7 in) long by 8–23 cm (3.1–9.1 in) wide, and are held on robust petioles that are 2–4 cm (0.8–1.6 in) long. Leaf margins are entire.^[3]

Fragrant white flowers are borne on 25–40 cm (10–16 in) long by 30 cm (12 in) wide panicles from June to August. The corolla tube is 2.5–3 mm long with 2 mm wide obtuse lobes. Tectona grandis sets fruit from September to December; fruits are globose and 1.2-1.8 cm in diameter.^[3] Flowers are weakly protandrous in that the anthers precede the stigma in maturity and pollen is shed within a few hours of the flower opening.^[4] The flowers are primarily entomophilous (insect-pollinated), but can occasionally be anemophilous (wind-pollinated).^[5] A 1996 study found that in its native range in Thailand, the major pollinator were species in the Ceratina genus of bees.^[4]

Distribution and habitat

Tectona grandis is one of three species in the genus Tectona. The other two species, T. hamiltoniana and T. philippinensis, are endemics with relatively small native distributions in Myanmar and the Philippines, respectively.^[6] Tectona grandis is native to India, Indonesia, Malaysia, Myanmar, northern Thailand, and northwestern Laos.^[3][4]

Tectona grandis is found in a variety of habitats and climatic conditions from arid areas with only 500 mm of rain per year to very moist forests with up to 5,000 mm of rain per year. Typically, though, the annual rainfall in areas where teak grows averages 1,250-1,650 mm with a 3-5 month dry season.^[7]

Botanical history

Tectona grandis was first formally described by Carl Linnaeus the Younger in his 1782 work Supplementum Plantarum.^[8] In 1975, Harold Norman Moldenke published new descriptions of four forms of this species in the journal Phytologia. Moldenke described each form as varying slightly from the type specimen: T. grandis f. canescens is distinguished from the type material by being densely canescent, or covered in hairs, on the underside of the leaf, T. grandis f. pilosula is distinct from the type material in the varying morphology of the leaf veins, T. grandis f. punctata is only hairy on the larger veins on the underside of the leaf, and T. grandis f. tomentella is noted for its dense yellowish tomentose hairs on the lower surface of the leaf.^[9]

Cultivation

Teak is a yellowish brown timber with good grains and texture. It is used in the manufacture of outdoor furniture, boat decks, and other articles where weather resistance is desired. It is also used for cutting boards, indoor flooring, countertops and as a veneer for indoor furnishings.

Teak, though easily worked, can cause severe blunting on edged tools because of the presence of silica in the wood. Teak's natural oils make it useful in exposed locations, and make the timber termite and pest resistant. Teak is durable even when not treated with oil or varnish. Timber cut from old teak trees was once believed to be more durable and harder than plantation grown teak. Studies have shown^[10] Plantation Teak performs on par with old-growth teak in erosion rate, dimensional stability, warping, and surface checking, but is more susceptible to color change from UV exposure.

The vast majority of commercially harvested teak is grown on teak plantations found in Indonesia and controlled by Perum Perhutani (a state owned forest enterprise) that manages the country's forests. The primary use of teak harvested in Indonesia is in the production of outdoor teak furniture for export.

Teak consumption raises a number of environmental concerns, such as the disappearance of rare old-growth teak. However, its popularity has led to growth in sustainable Plantation Teak production throughout the seasonally dry tropics in forestry plantations. The Forest Stewardship Council offers certification of sustainably grown and harvested teak products. Propagation of teak via tissue culture for plantation purposes is commercially viable.^[11]

Much of the world's teak is exported by Indonesia and Myanmar. There is also a rapidly growing plantation grown market in Central America (Costa Rica) and South America.

Hyblaea puera, a moth native to southeast Asia, is a teak pest whose caterpillar feeds on teak and other species of trees common in the region.^[12]

Uses

Teak is used extensively in India to make doors and window frames, furniture, and columns and beams in old type houses. It is very resistant to termite attacks. Mature teak fetches a very good price. It is grown extensively by forest departments of different states in forest areas.

Leaves of the teak wood tree are used in making Pellakai gatti (jackfruit dumpling), where batter is poured into a teak leaf and is steamed.^{[citation needed]} This type of usage is found in the coastal district of Udupi in the Tulunadu region in South India. The leaves are also used in gudeg, a dish of young jackfruit made in Central Java, Indonesia, and give the dish its dark brown color.

Teak is used as a food plant by the larvae of moths of the genus Endoclita including E. aroura, E. chalybeatus, E. damor, E. gmelina, E. malabaricus, E. sericeus and E. signifer and other Lepidoptera including Turnip Moth.

Teak is used extensively in boat decks, as it is extremely durable and requires very little maintenance. The teak tends to wear in to the softer 'summer' growth bands first, forming a natural 'non-slip' surface. Any sanding is therefore only damaging.^{[citation needed]} Use of modern cleaning compounds, oils or preservatives will shorten the life of the teak,^{[citation needed]} as it contains natural teak-oil a very small distance below the white surface. Wooden boat experts will only wash the teak with salt water, and re-caulk when needed.^{[citation needed]} This cleans the deck, and prevents it from drying out and the wood shrinking. The salt helps it absorb and retain moisture, and prevents any mildew and algal growth. People with poor knowledge often over-maintain the teak, and drastically shorten its life.^{[citation needed]}

Propagation

Tree in new leaves in Kolkata, West Bengal, India.

Teak is propagated mainly from seeds. Germination of the seeds involves pretreatment to remove dormancy arising from the thick pericarp. Pretreatment involves alternate wetting and drying of the seed. The seeds are soaked in water for 12 hours and then spread to dry in the sun for 12 hours. This is repeated for 10–14 days and then the seeds are sown in shallow germination beds of coarse peat covered by sand. The seeds then germinate after 15 to 30 days.^[13][14]

Clonal propagation of teak has been successfully done thorough grafting, rooted stem cuttings and micro propagation. While bud grafting on to seedling root stock has been the method used for establishing clonal seed orchards that enables assemblage of clones of the superior trees to encourage crossing, rooted stem cuttings and micro propagated plants are being increasingly used around the world for raising clonal plantations.^{[citation needed]}

References

External links

Media related to Tectona grandis at Wikimedia Commons

•  "Teak". The New Student's Reference Work. Chicago: F. E. Compton and Co. 1914.