Common name: Tree of heaven

Native to central and north India, this multi-purpose tree grows fast to heights of up to 25 m (80 ft) in its natural habitat, though it is more commonly 15 to 20 m (50 to 65 ft) tall in cultivation. It develops a straight trunk with smooth, light grey bark that darkens and roughens with age, and a densely branched oval to broadly rounded crown.

The leaves are large, up to a meter long and feather-like, being made up of up dark green, lance-shaped leaflets with toothed margins, arranged in near opposite pairs along the length. They cast a dense shade when on the tree, but in the dry season they fall, leaving the branches bare until the rainy season when the new leaves start to grow.

The flowers are small and insignificant, greenish-yellow, either female or male on the same tree, in loosely-formed clusters at the tips of the branches. They come into bloom at around the same time as the new leaves start to grow and are succeeded by thin, winged, paper-like seedpods that contain one to two seed.

Use

It produces a light-weight wood, in the 400 to 450 kgs per cubic meter (23 to 28 lbs per cubic ft) range, with low natural resistance to rot, decay and wood-boring insects. This classes it as a non-durable softwood, with low suitability for outdoor use and heavy construction generally. The heartwood is whitish, becoming light grey on exposure.

Well-formed logs are sawn into planks for making boxes, crates and other light articles such as pencils. Misshapen or small diameter logs are split into matchsticks or are processed into paper pulp for making paper products such as newsprint.

Though the wood is light-weight and not ideal for firewood, due to its low caloric value, which results in it quickly burning to ash, it is widely used for this purpose in its native range, in part because the tree is fast-growing and coppices well (regrows after being cut back to ground-level).

The leaves have a high crude protein content, approaching 20% of their dry weight, and are fed to small livestock, particularly to goats. They are usually dried, ground and mixed with other feed ingredients to produce a balanced, highly nutritious feed concentrate.

It sometimes serves as a street and shade tree in its native range, with potential to also serve as a pioneer species, especially for reclaiming and rehabilitating barren lands, on account of its fast growth, drought tolerance and ability to  coppice or regenerate easily.

Climate

Grows naturally in sub-humid subtropical and tropical lowland to mid-elevation climates, generally areas with annual lows of 16 to 21°C, annual highs of 27 to 35°C, annual rainfall of 400 to 2000 mm and a dry season of 6 to 9 months.

Growing

New plants are grown from seed and root cuttings. Seedpods planted whole give the best results and benefit from pre-soaking in water three days prior to planting. Seedlings need periodic watering after planting out in dry climates until they become established, which is around twelve to eighteen months.

Performs best on free-draining loam and sand soils of an acid to neutral nature, generally with a pH of 5.0 to 7.0 and on sites with full sun exposure. It has poor tolerance of poorly-drained, waterlogged soils or shade conditions.

Problem features

There does not appear to be any records of its escape and naturalisation anywhere in the world. However, the seed can be carried a considerable distance on the wind and there are reports of dense stands being created from seed dispersed from a single parent tree. It is also known to sucker vigorously from the roots.

Books

• Dastur, J. F. 1964, Useful plants of India and Pakistan : a popular handbook of trees and plants of industrial, economic, and commercial utility, 2nd ed., D. B. Taraporevala Sons, Bombay

• Hocking, D. 1993, Trees for drylands, International Science Publisher, New York

• Howes, F. N. 1949, Vegetable gums and resins, Chronica Botanica Company, Waltham, Massachusetts

• Krishen, P. 2006, Trees of Delhi : a field guide, Dorling Kindersley Publishers, Delhi

• Little, E.L. Jr. 1983, Common fuelwood crops: a handbook for their identification, McClain Printing Company, Parsons, West Virginia

• Luna, R. K 1996, Plantation trees, International Book Distributors, Dehradun, Uttarakhand

• National Research Council (Board on Science and Technology for International Development) 1983, Firewood crops : shrub and tree species for energy production (Volume 2), The National Academies Press, Washington D. C.

• Parrotta, J. A. 2001, Healing plants of peninsular India, CABI Publishing, Wallingford, Oxfordshire

• Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia

• Sheikh M. I. 1993, Trees of Pakistan, USAID Forestry Planning and Development Project, Pictorial Printers, Islamabad

• Singh, R. V. 1982, Fodder trees of India, Oxford & IBH Publishing Company, New Delhi

• Troup, R.S. & Joshi, H. B. 1975 to 1981, Silviculture of Indian Trees (3 volumes), Government of India Publications, New Delhi

Articles, Journals, Reports and Working Papers

• Joint FAO/ECE/ILO Committee on Forest Technology, Management, and Training. 2003. Harvesting of non-wood forest products: seminar proceedings. Ministry of Forestry of Turkey, Ankara.

• Singh, A. B., & Kumar, P. (2003). Aeroallergens in clinical practice of allergy in India. An overview. Annals of Agricultural and Environmental Medicine, 10(2), 131-136.

• Singh, K. P. & Kushwaha, C. P. 2006, Diversity of flowering and fruiting phenology of trees in a tropical deciduous forest in India, Oxford University Press