Common name: Bitterwood

Bitterwood, as its name implies, is named for the bitter properties of its wood, which has long been used as a flavouring agent by the food, beverage and pharmaceutical industries.

The tree's native range is limited to the Caribbean islands of Jamaica, Hispaniola and Puerto Rico, where it occurs mainly in wet limestone forests.

It may reach up to 25 m (82 ft) in height, though it is typically 6 to 20 m (20 to 65 ft) tall in natural forests, with a slender trunk and narrow crown of ascending branches, shaped by its proximity to other trees.

Leaves are large, 15 to 36 cm (0.5 to 1.2 ft) long and feathery, consisting of seven to thirteen narrowly elliptical, prominently veined green leaflets, arranged in pairs along the length and with an extra leaflet at the tip. They remain on the tree in all seasons.

Flowers are small and insignificant, greenish-white, either bisexual or male on the same tree and borne in small clusters arising at the base of the leaf. They bloom in the rainy season, coinciding with summer to autumn in its native range. Fertilised flowers develop into round green fruit, about 0.5 cm (0.2 in) in diameter, ripening to near black with pulpy flesh surrounding a single seed.

Use

The wood yields, by aqueous extraction, a bitter substance known as 'Quassin', which is is about fifty times more bitter than Quinine, from Cinchona (Cinchona calisaya). It has long been used as a bittering agent in non-alcoholic and alcoholic drinks, including grapefruit based soft drinks and branded alcoholic beverages such as 'Campari', the Italian aperitif, with its distinctive bitter-sweet taste and pink-red colour. It is also used as a bitter agent in marmalades and is a credible substitute for Hops (Humulus lupulus), used in brewing beer and ale. 

The wood is harvested almost exclusively from wild trees, which are felled and the heartwood chipped, dried and bagged for export. It is a pale yellow, lightweight wood, averaging around 500 kgs per cubic meter (31 lbs per cubic foot) and has good natural resistance to wood-boring insects, though not rot and decay. 

The insecticidal properties of the wood have also seen it being used in aqueous solutions as a natural insecticide, particularly against aphids and other sucking insects. However, it should not be sprayed onto plants bearing edible leaves or fruit, as it will impart its bitter flavour, which is difficult to undo.

Over-exploitation of the tree for its wood has led to its listing as a vulnerable tree species by the International Union for Conservation of Nature and Natural Resources (IUCN), bringing attention to the need to protect the remaining wild trees.

The tree is also considered an important resource for wildlife in its native range, supporting many wild birds species that feed on the fruit.

Health use

Quassin is occasionally used in laxative preparations. And a tea brewed using the wood is given as a tonic in parts of its native range to stimulate the appetite and aid digestion.

Climate

Grows naturally in moderately humid to very humid tropical lowland to mid-elevation climates, generally frost-free areas with annual lows of 17 to 23°C, annual highs of 26 to 33°C, annual rainfall of 1800 to 3800 mm and a dry season of 3 months or less.

Growing

Bitterwood is not usually cultivated, though seedlings are sometimes made available, free of charge, by government-run forestry departments in its native region to encourage the planting of native trees, particularly endangered ones.

Performs best on loam, sandy-loam, loamy-sand and limestone soils of a slightly acid to alkaline nature, generally with a pH 6.0 to 8.0 and on sites with full to partial sun exposure.

Problem features

Birds are known to eat the fruit and disperse the seed, which germinate readily in sun or shade. This gives it the ability to regenerate in native forests and may make it a high-risk weed species in non-native areas.

Excessive amounts of Quassin may irritate the digestive system and vomiting.

Books

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

• Cassidy, F. G. & Le Page, R. B. 1980, Dictionary of Jamaican English, 2nd ed., Cambridge University Press, Cambridgeshire

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

• Duke, J.A. 1993, CRC Handbook of Alternative Cash Crops, CRC Press, Boca Raton, Florida

• Fawcett, W. & Rendle, A. B. 1920, Flora of Jamaica, containing descriptions of the flowering plants known from the island, Department of Botany, British Museum (Natural History), London

• Fawcett, W. 1891, Economic plants, An index to economic products of the vegetable kingdom in Jamaica, Jamaica Government Printing Establishment, Kingston

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

• 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

• Little, E. L. 1974, Trees of Puerto Rico and the Virgin Islands, Vol. 2, United States Department of Agriculture (USDA), Washington D.C.

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

• 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

• Record, S. J. & Hess, R. W., 1972, Timbers of the New World, Yale University Press, New Haven, Connecticut & Arno Press, New York

• Seidemann, J. 2005, World spice plants: economic usage botany taxonomy, Springer-Verlag, Berlin

Articles, Journals, Reports and Working Papers

• Douglas M. & Heyes J. & Smallfield B. 2005, Herbs, Spices and Essential Oils Post-Harvest Operations in Developing Countries, Food and Agriculture Organization of the United Nations (FAO), Rome