Morus (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Morus L.

Protologue: Sp. pl. 2: 986 (1753); Gen. pl., ed. 5: 424 (1754).

Family: Moraceae

Chromosome number: x= 14; M. alba: n= 14, 28; M. australisPoir.: n= 14; M. macroura: 2n= 28, 56

Vernacular names

• Mulberry (En)
• Mûrier (Fr)
• Indonesia: murbei (general)
• Malaysia: bebesaran (general)
• Philippines: amoras (Filipino)
• Cambodia: moon
• Laos: mon
• Thailand: mon
• Vietnam: dâu tằm, tằm tang.

Origin and geographic distribution

Morus comprises some 12 species occurring in all tropical and temperate regions of the world. Only one species ( M. macroura ) seems to be native in Malesia and several others have been introduced.

Uses

The attractive wood of Morus is used mainly for furniture and cabinet work, but also for beams, posts, flooring and bridge building. In India the wood of M. alba is additionally used for boats, turnery, sporting goods and buggy shafts. Wood of M. macroura yields a medium-quality firewood.

M. alba is much better known as the chief mulberry used to rear silkworms and grown for its tasty fruits. In India it is fairly frequently used in agroforestry. It is occasionally planted as a roadside tree, and is highly valued as medicinal plant.

Production and international trade

In India M. alba has been managed quite extensively in Dalbergia sissoo Roxb. ex DC. plantations where it establishes spontaneously. Within Malesia the use of mulberry wood is limited and on a local scale only.

Properties

Morus yields a medium-weight hardwood with a density of 670-850 kg/m³at 15% moisture content. Heartwood yellow or yellowish-brown, darkening to golden or red-brown upon exposure, sharply demarcated from the up to 4 cm wide, white or pale yellow sapwood; grain straight; texture moderately coarse and even in semi-ring-porous material, uneven in ring-porous material; wood lustrous at first, becoming dull with age, with attractive silver grain. Growth rings distinct due to large earlywood vessels, ring-porous; vessels very small (in latewood) to moderately large (in earlywood), solitary and in radial multiples of 2-3, occasional clusters in smaller vessels, tyloses and white deposits present; parenchyma paratracheal vasicentric, and apotracheal in marginal or seemingly marginal bands; rays moderately fine to medium-sized; ripple marks absent. M. macroura wood resembles teak ( Tectona grandis L. f.).

In seasoning, the wood of M. alba has a tendency to warp. Kiln drying of M. macroura boards resulted in no degrade at all. The wood is easy to work and machine, finishes smoothly, and quarter-sawn boards present a decorative silver grain figure. The wood is moderately hard to hard, tough and very flexible when steamed. It is fairly durable when exposed to the weather or in contact with the ground and not susceptible to insect or fungal attack.

The energy values of the sapwood and the heartwood of M. alba are 19 260 kJ/kg and 20 380 kJ/kg, respectively.

See also the table on microscopic wood anatomy.

Botany

Deciduous, monoecious or dioecious shrubs or small to fairly large trees up to 35 m tall; bole up to 150 cm in diameter, without buttresses; bark exuding white or yellowish-white latex. Leaves distichous, simple to 3-lobed, dentate, palmately 3-veined at base; stipules lateral, caducous, coriaceous. Inflorescence axillary, pendulous. Flowers with 4, free, imbricate tepals. Male flowers in a catkin-like raceme; stamens 4; pistillode top-shaped. Female flowers in a long or short spike; tepals becoming succulent in fruit; ovary enclosed, 1(-2)-locular with a single ovule, style 2-partite. Fruit a drupaceous syncarp. Seedling with epigeal germination; cotyledons emergent; hypocotyl elongated; leaves often palmately or pinnately lobed.

In India 20-year-old coppice shoots of M. alba showed a mean annual diameter increment of 1.5 cm and a mean annual height increment of 1.0 m; early growth was very fast: 4.5 m in the first two years. In Java M. macroura has been observed flowering in June-December. The sporadically collected fruits mostly proved to contain no seeds. Seeds are dispersed by water and by birds, but fruits on long, pendulous spikes may also be dispersed by bats.

The number of species within Morus is often greatly overestimated because many cultivated forms which have subsequently been described as species have arisen through hybridization.

Ecology

M. macroura is found in evergreen rain forest or sometimes on fallow land, often on volcanic soils, at 400-2500 m altitude.

Silviculture Morus can be easily propagated by seed, by cuttings and by tissue culture. When fruits are soaked in water for a few days, seeds can be released by gently rubbing the pulpy mass followed by rinsing with water. In India M. alba is raised from seeds and seedlings are pricked out when 10-15 cm tall. All but a few terminal leaves are stripped ("striplings") before seedlings are planted during the cold season or at the beginning of the rainy season. Plantations are managed by coppicing, which stimulates vigorous growth. M. macroura is also propagated by cuttings. M. alba is considered shade-tolerant.

Genetic resources and breeding

M. macroura is rare and almost extinct in West Java. There are no recent records of its occurrence in Sumatra.

Prospects

In view of the apparently good quality of the timber of M. macroura and its expected rapid growth, silvicultural trials are desirable.

Literature

70, 73, 238, 261, 364, 399, 406, 436, 458, 595, 751, 861, 874, 974, 1038, 1104, 1169.