Teak (Tectona grandis) is one of the most renowned tropical hardwood trees native to Africa and Southern Asia, particularly in countries like India, Myanmar (Burma), Thailand, and Indonesia. It is a large, deciduous tree that occurs in mixed hardwood forests. Myanmar’s teak forests account for nearly half of the world’s naturally occurring teak
Teak wood has a leather-like smell when it is freshly milled and is particularly valued for its durability and water resistance. The wood is used for boat building, exterior construction, veneer, furniture, carving, turnings, and various small projects. Its commercial value has made teak to be introduced and cultivated in many tropical regions around the world including Africa, Central and South America, and the Caribbean.
A mature teak tree can grow to a height of approximately 98 to 131 feet in natural conditions. The trunk diameter at breast height (DBH, which is typically measured at 1.3 meters or about 4.5 feet above the ground) can be 1 to 1.5 meters. However, in optimal conditions or with selective breeding for timber production, they might not always reach the full height due to earlier harvesting.
Teak is semi-deciduous or deciduous in drier climates, losing its leaves during the dry season to conserve water. Teak leaves are large with an elliptical or obovate shape. They are rough to the touch, almost sandpaper-like due to tiny hairs, especially on the underside. Young leaves can be reddish or purplish, turning to a vibrant green as they mature. The underside of the leaf is lighter in color. The leaves are opposite or sometimes whorled on the stem.
The bark is usually grey to brown in color, with the outer bark often appearing somewhat mottled or with slight variations in shade. Young trees have relatively smooth bark, but as the tree ages, the bark becomes thick, rough, and deeply furrowed. The furrows run longitudinally along the trunk. In some cases, the bark might peel off in long, fibrous strips, especially in older trees.
Teak flowers are small, white, or off-white and are grouped in large, erect, terminal panicles (a loose branching cluster of flowers) that can be up to 45 cm (18 inches) long. The flowers are pleasantly fragrant. Flowering usually occurs during the rainy season. In its native regions, this means from June to September. Each flower is bisexual, containing both male and female reproductive parts. They have a five-lobed calyx and corolla, with several stamens.
Teak flowers are pollinated by insects. After flowering, teak trees produce fruit which are drupes, containing seeds. The fruit is a small, hard, woody sphere, often surrounded by an inflated calyx which aids in wind dispersal.
Teak trees grow relatively quickly in their first few years if conditions are optimal, with growth rates that can be as much as 1.5 to 2 meters (approximately 5 to 6.5 feet) per year in height under ideal tropical conditions with good soil, water, and sunlight. After the initial rapid growth phase, the growth rate slows down. Over time, the average growth in height might reduce, but the tree continues to increase in girth.
Teak trees can live for over 100 years quite commonly. Some trees can live much longer, with lifespans reaching up to 150 years or more in optimal conditions. For commercial timber purposes, teak is often considered mature enough for harvesting between 20 to 60 years, with 25-50 years being common for good quality wood.
Factors Affecting Growth and Lifespan
- Soil Quality: Rich, well-drained soils enhance growth rates.
- Water: Adequate rainfall or irrigation during the growing season is crucial. Teak has a pronounced growth spurt during the monsoon or rainy season.
- Climate: Teak thrives in tropical climates with a distinct wet and dry season. Continuous high humidity or too much waterlogging can be detrimental.
- Spacing: In plantations, spacing between trees affects growth rates; closer spacing can lead to taller trees with less lateral growth, while wider spacing allows for more canopy development but might slow vertical growth.
- Pruning and Thinning: Management practices like pruning lower branches to reduce knots in the wood or thinning to give remaining trees more space can influence growth.
- Genetics: Certain strains or provenances of teak might be selected for faster growth or better wood quality, affecting both growth rate and potential lifespan.
Types of Teak Tree (Tectona grandis)
Tectona grandis – This is the common teak, native to south and southeast Asia, mainly India, Indonesia, Myanmar, Thailand, and Malaysia. Here are some distinctions within this species:
- Burmese Teak – Often considered the best quality, primarily from Myanmar, known for its golden brown color, fine grain, and high oil content.
- Indian Teak – Widely used and known for its durability and resistance to termites and weather conditions.
- Indonesian Teak – Also of high quality, though it might differ slightly in color and grain from Burmese teak.
- African Teak – While not a different species of Tectona, teak from Africa might refer to plantations of Tectona grandis or might be confused with other timber like Iroko (which isn’t true teak but is often called African Teak).
Tectona hamiltoniana – This is a lesser-known species of teak, found in Myanmar. It’s not as widely used or recognized as T. grandis due to limited distribution and different wood properties.
Tectona philippinensis – Known as Philippine teak, this species is endemic to the Philippines. It’s used locally for timber but is less known internationally compared to T. grandis.
Cultivars and Variants: Within Tectona grandis, there might be cultivars developed for faster growth, better wood quality, or disease resistance, particularly in plantations. However, these are not always classified as different “types” in botanical terms but rather as improved selections or clones for forestry.
Teak (Tectona grandis) Wood
Physical Properties
- Color: The wood has a golden to medium brown heartwood, which darkens with age. The sapwood is pale yellow and clearly demarcated from the heartwood.
- Grain: The grain is usually straight, though it can occasionally be wavy or interlocked, giving it a beautiful texture.
- Texture: Teak has a coarse, uneven texture with an oily feel due to its high natural oil content.
- Density and Hardness: It’s a dense hardwood, with a high degree of hardness that contributes to its durability. On the Janka hardness scale, it scores around 1,070 to 1,155 lbf (pound-force), making it resistant to denting and wear.
Workability
- Machining: Despite its hardness, teak works well with both hand and machine tools, although its silica content can dull cutting edges faster than many other woods.
- Finishing: Teak takes finishes well, but due to its oily nature, it’s often left untreated. When finishes are applied, they might require special preparation to adhere properly.
- Gluing: It can be challenging to glue because of the oils, but with the right preparation and adhesives, it glues satisfactorily.
Uses
- Outdoor Furniture: Its durability and resistance to elements make it perfect for garden and patio furniture.
- Marine Applications: Used for decking, trim, and interior joinery in boats and ships.
- Indoor Furniture: High-end furniture, cabinets, and flooring.
- Construction: Doors, window frames, and beams where durability is required.
- Decorative: Veneers, carvings, turnery, and inlays due to its attractive grain and color.
Cultivation of Teak Tree (Tectona grandis)
Site Selection
- Climate: Teak thrives in tropical climates with a distinct wet and dry season. It requires temperatures between 27°C to 36°C (80°F to 97°F) for optimal growth.
- Rainfall: Ideal annual rainfall ranges from 1,200 to 2,500 mm, with a pronounced dry season no longer than four months.
- Soil: Well-drained, fertile soils with good depth are best. Teak does well in soils with a pH between 6.5 and 7.5. Sandy loam or lateritic soils are commonly preferred.
- Altitude: Typically, teak is cultivated at altitudes below 700 meters (2,300 feet), although it can grow at higher elevations with less optimal conditions.
Planting
- Source of Seeds: Use seeds or seedlings from reliable sources with known provenance for better growth rates and wood quality. Sometimes, stumps (root-shoot cuttings) are used for plantations due to their faster initial growth.
- Pre-treatment: Seeds benefit from soaking in water for 24-48 hours before sowing to enhance germination.
- Spacing: Plant spacing can vary but commonly used spacings are 2m x 2m to 3m x 3m, allowing for an eventual thinning process to give the best trees more room to grow.
- Time of Planting: Planting should coincide with the onset of the rainy season to ensure enough moisture for seedling establishment.
Care and Maintenance:
- Weeding: Initial years require regular weeding to reduce competition for nutrients and water.
- Thinning: Thinning is crucial in teak plantations. It involves removing weaker trees to give more space to the healthier ones, usually done several times during the growth cycle.
- Pruning: Pruning lower branches helps in producing clear, knot-free wood. This is often done up to a height of 2-3 meters to improve timber quality.
- Irrigation: While teak is drought-resistant once established, supplemental irrigation during dry spells in the first few years can significantly enhance growth.
- Fertilization: Although teak can grow in relatively poor soils, applying organic or chemical fertilizers can improve growth rates, particularly in plantation settings.
Pest and Disease Management
- Pests: Teak defoliators and skeletonizers are common pests. Biological controls, like using Bacillus thuringiensis, or selected pesticides can be used.
- Diseases: Root rot can be an issue in poorly drained soils. Ensuring good drainage is key to prevention.