Local names:
Gujarati (kandol,kadai,kadayo,kagdoli), Hindi (kulu,kadaya,gulu,gular,karaya), Tamil (kavili,kavalam,villay putali,errapunikichettu,senthanuku,tabsu), Trade name (karaya,kadaya), Urdu (konda-tamara)
Sterculia urens is a medium-sized, deciduous tree to 15 m in height, usually with a clean, crooked, short bole up to 2 m DBH; branches large, spreading; bark thick, greyish-white or reddish, smooth, shining with a thin, white transparent outer coat, peeling off in papery flakes. Leaves on long petioles, crowded at the ends of branches, palmately 5-lobed, 20-30 cm diameter; tomentose beneath, glabrous above, entire, acuminate; stipules caducous. Flowers greenish yellow, small, in terminal panicles; follicles 4-6, ovoid-oblong, about 2.5 cm diameter, coriaceous, red, covered with stinging hairs. Fruit consists of 5 sessile, radiating, ovate-lanceolate hard, coriaceous carpels, 7.5 cm long, red when ripe, covered outside with many stiff bristles. Seeds 6 mm long, oblong, dark chestnut-brown, 3-6 per carpel. The generic name is based on the Latin name ‘stercus’, meaning ‘manure’, which refers to the smell of the flowers and leaves of some species. The specific name means stinging in reference to the hairs on flowers.
Ecology
Karaya usually occurs in dry, tropical deciduous forests and is often associated with Boswellia serrata. The tree occupies hilltops, exposed ridges, rocky crevices, eroded slopes and similar habitats. It is a xerophytic species, very resistant to drought and will grow on the poorest of dry stony soils. It is gregarious on ferruginous soils.
Native range
India, Myanmar, Sri Lanka
Tree management
S. urens is a strong light-demander but seedlings and saplings tolerate shading and are prone to fire damage. The tree does not stand competition and should be protected from browsing animals. It coppices when young.
Seed storage behaviour is orthodox. Viability is maintained for more than 3 years in hermetic storage at room temperature with 13 % moisture content. There are about 5 300 seeds/kg.
Karaya usually occurs in dry, tropical deciduous forests and is often associated with Boswellia serrata. The tree occupies hilltops, exposed ridges, rocky crevices, eroded slopes and similar habitats. It is a xerophytic species, very resistant to drought and will grow on the poorest of dry stony soils. It is gregarious on ferruginous soils.
Propagation is by seed, which are sown in April. Germination takes 10-15 days and gives nearly 100 % seedlings that reach 15-20 cm height by July.
It is useful for reclaiming bare, rocky land.
Trees exude gum karaya used in foodstuffs as emulsifiers, stabilizers and thickeners. Seeds are eaten after roasting. Seeds and young tender roots are eaten in times of famine.
The tree is used as a fuelwood.
Fibre: The bark can be stripped off easily and yields a useful fibre suitable for making coarse cloth and bud ropes.
Timber: Sap wood is pale greyish-white, heartwood distinct, red; heavy to very heavy, very strong and very hard, but poor in splitting and retention of shape. It planes and turns to a smooth finish and may also be suitable after seasoning and the adoption of suitable joining techniques for door and window frames, furniture and joinery. It is considered suitable for use as posts, beams, rafters and tool handles.
Gum or resin: The tree yields gum karaya from the pith and cortex. The main constituent of the resin is a phlobatannin, containing 3 phenolic OH groups. A large part of the Karaya is used in the pharmaceutical Industry as a bulk laxative and as a denture