Uses
Although soft and comparatively weak, the wood of Hibiscus is quite attractive and used for local house building, interior trim, moulding, wagon frames, vehicle shafts, spokes and rims of wheels, gunstocks, household implements, tool handles, scabbards, musical instruments, picture frames, carving, package and fittings, toothpicks, matches and matchboxes, fencing and occasionally also for marquetry and barrel hoops. It has been reported to last very long in contact with water and has been applied for ship and boat building (frames and keels). The wood is also suitable for the manufacture of plywood, hardboard and probably also for that of paper. It yields a good firewood. The flexible branches have been used as fishing rods.
The bark of several timber-yielding species, notably from that of H. tiliaceus, can be used to manufacture a good quality rope which is also used for caulking boats. In Java the bark fibres are called "lulub waru"" and in southern Sumatra they are also used for plaiting mats. H. macrophyllus and H. tiliaceus have been used to reforest eroded land, the latter also as a shade tree, hedge or wind-break, especially along the seashore, and, because of its showy yellow flowers with a purple centre, also as an ornamental. The bark and leaves of H. tiliaceus are used medicinally, especially to relieve coughs, sore throats and tuberculosis.
Botany
Deciduous or evergreen, small to medium-sized trees up to 30 m tall, or shrubs or herbs; bole branchless for up to 12 m, up to 80 cm in diameter, sometimes with small buttresses; bark surface smooth to shallowly cracked or minutely fissured, lenticellate, grey or grey-fawn, inner bark fibrous, pinkish-brown, wood with slight, clear, slimy sap. Indumentum with stellate hairs and/or scales. Leaves arranged spirally, simple, entire to deeply lobed, palmately veined, stipulate. Flowers axillary, solitary or in a raceme or panicle, 5-merous; epicalyx with 3-many free or almost free segments; calyx 5-lobed or 5-parted; petals free, often large; staminal column bearing anthers throughout or in the upper half; ovary superior, 5- or 10-locular with 3-many ovules per cell, style 1, apically divided into 5 branches. Fruit a dehiscent capsule with a persistent calyx and epicalyx. Seed globose to kidney-shaped. Seedling with epigeal germination; cotyledons emergent; hypocotyl elongated; all leaves arranged spirally.
Root nodules have been observed in H. tiliaceus in the Solomon Islands, where it is explicitly used for soil restoration during fallow, but atmospheric nitrogen fixation has not been confirmed. Early growth of H. tiliaceus is rapid and in 2-3 years the tree is large enough to provide shade. In Java it attained a diameter of 42 cm in 15 years, with sapwood being 3-5 cm in width for H. tiliaceus subsp. tiliaceus and 6-7 cm for subsp. similis (Blume) Borss. Waalk. On moderately fertile to fertile soils H. tiliaceus attained a mean diameter of 24-31 cm and a mean height of 20-28 m in 11 years. H. tiliaceus develops according to Scarrone's architectural tree model, characterized by an orthotropic rhythmically active terminal meristem which produces an indeterminate trunk bearing tiers of branches, each branch-complex orthotropic and sympodially branched as a result of terminal flowering. In Java H. tiliaceus flowers more or less throughout the year, but on other Indonesian islands flowering is restricted to 1-3 months/year. Flowers are pollinated by insects and birds. Seeds of H. tiliaceus can float in seawater for several months and are commonly found along the shore.
H. tiliaceus is very polymorphic and has been divided into 5 subspecies. The name H. papuodendron Kosterm. ("bulolo ash"") occasionally appears in literature concerning Papua New Guinea timbers. The correct name is probably Papuodendron lepidotum C.T. White. Although Papuodendron is hardly distinct from Hibiscus, it is placed by some in the Malvaceae and by others in the Bombacaceae.
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