Shorea robusta

Shorea robusta, the sal tree, sāla, shala, sakhua, or sarai, is a species of tree in the family Dipterocarpaceae. The tree is native to India, Bangladesh, Nepal, Tibet and across the Himalayan regions.

Description

A tree. It loses some of its leaves during the year. It grows about 50 m high. The bark is rough and reddish brown with deep wide cracks along its length. The leaves have stalks. The stalks are 2-5 cm long. The leaves are 10-20 cm long by 5-13 cm wide. They are oval and leathery. They taper to the tip. They are shiny when mature. The base is rounded or heart shaped. The flowers are yellow. They are in open flower arrangements in the axils of leaves or at the ends of branches. The flowers are small but in large numbers. The fruit is oval. It is 10-15 cm across. It is pale yellowish or green in colour. It is hairy with wing-like sepals at the base. It does not split open. It is one seeded with 5 unequal wings. The seed is oval with fleshy green seed leaves. These contain fatty oil.

Edible Uses

The seeds are roasted and can also be boiled into a porridge together with the flowers of Bassia latifolia and the fruits of Dolichos biflorus. They can be ground into a coarse flour to make bread, and the plant serves as a famine food. A de-fatted kernel powder known as sal seed cake contains around 50% starch along with proteins, tannins, and minerals; the physicochemical properties of this starch can be exploited for preparing canned food products. The seeds' chemical composition is approximately 10.8% water, 8% protein, 62.7% carbohydrate, 14.8% oil, 1.4% fibre, and 2.3% ash. The seeds also yield sal butter, an oil used in cooking as a substitute for ghee and as a replacement for cocoa butter in making chocolate. The fruit is occasionally eaten.

Traditional Uses

Roasted seeds are eaten. They are dried and ground into flour and then dried again and used for bread or with other ingredients like salt added. The seed oil remains solid at room temperature and after processing can substitute for Cocoa butter in the Chocolate industry. The fruit are occasionally eaten. CAUTION: The prolonged cooking and drying suggest some toxic substance needs to be removed. They contain tannins or phlobaphene. The flowers are used in curries.

Medicinal Uses

The resin is valued for treating dysentery, gonorrhoea, boils, and toothache. Leaf juice is used for dysentery, and warmed leaves are applied as a poultice to swollen areas of the body, with a reportedly quick effect; they are also placed on the stomachs of children with dysentery. Oil from the seeds is used to treat skin diseases.

Distribution

It is a subtropical plant. In Nepal plants grow to about 1400 m altitude. It grows on the outer ridges of hills. It suits hardiness zones 10-12.

Where It Grows

Asia, Australia, Bangladesh, Bhutan, China, Himalayas, India, Myanmar, Nepal, Northeastern India, SE Asia, Sikkim,

Cultivation

A plant of the tropics, where it is found at elevations up to 2,000 metres. It grows best in areas where annual daytime temperatures are within the range 28 - 34°c, but can tolerate 7 - 47°c. The plant can survive temperatures down to about -1°c. It prefers a mean annual rainfall in the range 1,500 - 3,500mm, but tolerates 1,000 - 7.300mm. There is usually a dry season of 4 - 8 months. Prefers a position in full sun, but tolerates light shade. Succeeds in most well-drained, fertile soils, though it prefers a moist sandy loam with good subsoil drainage. Prefers a pH in the range 5 - 6.7, tolerating 4.5 - 7.5. Young trees grow quickly, developing a long taproot at a very young age and attaining top heights of up to 6 metres after 6 years. Fruit and seed bearing begins around the age of 15 years, the tree then bears fruit regularly every 2 years or so, and a good seed-bearing year can be expected every 3 - 5 years. The tree responds well to coppicing. Rotations of 30 - 40 years are used when coppice regeneration is practised, and 80 - 160 years for high forest regeneration. The tree is very tolerant of forest fires, usually surviving them if not too small.

Propagation

The following is a general guide for the genus. Sow seed as soon as possible; no pre-treatment is required, though soaking for 12 hours before sowing is recommended. Sow in seedbeds covered with a 1:1 mixture of sand and soil, or a thin layer of sawdust. Fresh seed germinates well and rapidly. About two weeks after germination, when seedlings are 5–6cm tall, pot them individually into containers approximately 15 × 23cm with good drainage. A potting mix of forest soil and sand at 3:1 is recommended to introduce appropriate mycorrhizae. Grow seedlings in 50–60% sunlight, watering twice daily. Plant out when 30–40cm tall, after hardening off in full sunlight for one month.

Other Uses

When tapped, the tree produces large quantities of a whitish, aromatic, transparent resin known as lal dhuna, used to caulk boats and ships and as incense. In parts of the Upper Tista forests of the Darjeeling District, large lumps often measuring 450–600 cubic centimetres are found in the ground at the base of trees. The leaves are widely used to make plates and cups and for wrapping food. Seed oil is used for illumination. The bark yields tannins. The heartwood is dark reddish-brown with a whitish thin sapwood band; the grain is strongly spiralled and rather coarsely structured. The wood is hard, heavy, very durable, and highly resistant to termite attack, though seasoning can be problematic. It saws easily but is difficult to plane and turn due to its high resin content, and it tends to split when nailed. This important Indian hardwood is particularly suited to heavy-stress structural use in buildings, hydraulic engineering, ships, and railway cars; it is also used for poles, railway ties and posts, window frames, floors, and many other applications. Coppice shoots are used for household and agricultural implements, and the wood is an important local fuel source.

Production

In Sikkim seeds are available May to June.

Other Information

It is cultivated.

Notes

Chemical composition: Water = 10.8%. Protein = 8%. Carbohydrate = 62.7%. Oil = 14.8%. Fibre = 1.4%. Ash = 2.3%. Sal butter, used in cooking, is derived from the seeds.

Nutrition

Synonyms

Also Known As

Agrath, Bolsal, Dieng-blei, Gazari, Gugal, Hal-orang, Lon-mani-ingyin, Makka, Maramaram, Ral, Rengal, Sagua, Sakhua, Sakhu, Sakuwa, Sal, Salwa, Sekua, Sekuva, Sekwa, Seral, Shal, Taksal-kung

References (38)

• Acharya K. P. and Acharya, R., 2010, Eating from the Wild: Indigenous knowledge on wild edible plants in Parroha VDC of Rupandehi District, Central Nepal. International Journal of Social Forestry. 3(1):28-48
• Ambasta, S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 572
• Behera K. K., et al, 2008, Wild Edible Plants of Mayurbhanj District, Orissa, India. J. Econ. Taxon. Bot. Vol. 32 (Suppl.) pp 305-314
• Bole, P.V., & Yaghani, Y., 1985, Field Guide to the Common Trees of India. OUP p 97
• Cundall, P., (ed.), 2004, Gardening Australia: flora: the gardener's bible. ABC Books. p 1339

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