Common name: Malabar nut

Malabar nut or Vasaka nut is an ornamental and medicinal shrub originating in Pakistan, India and Southeast Asia.

It is a fast-growing shrub and may reach up to 5 m (16 ft) under favourable conditions, though it is more typically 2 to 3 m (7 and 10 ft) tall with multiple stems supporting a wide-spreading crown, often as wide as the plant is tall.

The leaves are elongated oval, up to 25 cm (10 in) long, on top bright green and prominently ribbed, underneath pale green. They remain on the plant throughout the year and give off an unpleasant odour when crushed.

The flowers are an unusual shape, having two large white lips with purple veining. They bloom in the dry winter season in its native range, tightly packed on erect flowers spikes and are soon followed by club-shaped seed capsules up to 2.5 cm (1 in) long. When mature, the light-brown seedpods pop open and expel their seed some distance from the parent plant.

Use

Due to their high potassium nitrate content, the leaves and young twigs are unpalatable and even poisonous to livestock. However, these properties help make the leaves valuable green manure. They are harvested and used in southern India to fertilise rice, tea (Camellia sinensis) and tobacco crops.

The leaves being unpalatable to livestock has led to its cultivation as a hedge in areas where free-roaming, browsing livestock can be a problem for gardeners. Its tolerance to salt spray makes it suitable for seaside gardens.

The wood is a valued firewood that burns cleanly for a long time, with little to no odour or spark. It is reported to have been used in the past for making charcoal for gunpowder.

It is reported as a major honey plant in Pakistan. Still, there is little to no reliable information on the honey, its colour, flavour, or the plant's value to bee forage more generally.

An infusion of the leaves is used as an insecticide in its native range against mosquitoes, flies and termites. The active ingredient is an alkaloid known as vasicine. Vasicine is toxic to insects and cold-blooded animals like fishes and frogs, but not to mammals.

Health use

Vasicine, the alkaloid in the leaves, is effective against coughs, asthma, bronchitis, excessive phlegm and similar respiratory ailments.  In traditional Indian or Ayurvedic medicine, it is prescribed as a treatment for such conditions.

Climate

Grows naturally in sub-humid to moderately humid subtropical and tropical lowland to mid-elevation climates, generally in frost-free areas with annual lows of 14 to 23°C, annual highs of 26 to 35°C, annual rainfall of 600 to 1700 mm and a dry season of 3 to 8 months.

Growing

New plants are usually grown from seed. Its showy foliage is at its best display when there is some protection from the mid-day sun, generally on sites with partial sun exposure to light shade.

It performs best on loam, sand and limestone soils of a neutral to alkaline nature, generally with a pH of 7.0 to 8.0. It has a high tolerance to salt, with growth reportedly unaffected by slight to moderate salinity conditions of up to 6 grams of dissolved salt per litre of water. Although also drought tolerant, plants need to be regularly watered until established.

Problem features

It is introduced in many countries outside of its native range and is reported to have become naturalised in most, with the result that it is listed as a serious weed in more than one reference publication. It can quickly escape cultivation, with escapees typically found on shaded sites where they grow to form dense thickets.

The whole plant gives off an unpleasant odour when brushed against.

Books

• Adams, C. D. 1972, Flowering plants of Jamaica, University of the West Indies, Mona, Greater Kingston

• Champion, H. G. & Seth, S. K. 1968, A revised survey of the forest types of India, Natraj Publishers, Dehradun, India

• Chevallier, A. 2000, Encyclopedia of herbal medicine, 2nd American ed., Dorling Kindersley, New York

• Crane, E., Walker, P. & Day, R. 1984, Directory of important world honey sources, International Bee Research Association, London

• 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

• Jacobson, M. 1958, Insecticides from plants : a review of the literature, United States Department of Agriculture (USDA), Washington D.C.

• Khan, I. A. & Abourashed, E. A. 2010, Leung's encyclopedia of common natural ingredients : used in food, drugs and cosmetics, 3rd edition, Wiley Publishing, Hoboken, New Jersey

• Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London

• National Research Council (Board on Science and Technology for International Development) 1980, Firewood crops : shrub and tree species for energy production (Volume 1), The National Academies Press, Washington D. C.

• Oakman, H. 1995, Harry Oakman's what flowers when : the complete guide to flowering times in tropical and subtropical gardens, University of Queensland Press, St. Lucia, Queensland

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

• Randall, R. P. 2002, A global compendium of weeds, R.G. and F.J. Richardson Press, Melbourne

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

Articles, Journals, Reports and Working Papers

• Dagar, J. C. & Singh, G. 2007, Biodiversity of Saline and Waterlogged Environments: Documentation, Utilization and Management, NBA Scientific Bulletin, (9), 78.

• National Research Council (Board on Science and Technology for International Development) 1990, Saline agriculture : salt-tolerant plants for developing countries, The National Academies Press, Washington D. C.