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 year-round.

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.

Edible uses

Natural flavouring - The wood yields, by aqueous extraction, a bitter substance known as 'Quassin', which 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 bittering 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, the heartwood chipped, dried, and bagged for export. It is a pale yellow, lightweight wood, averaging around 500 kg per cubic meter (31 lbs per cubic foot), with good natural resistance to wood-boring insects, though not to rot and decay.

Material uses

Natural insecticide - The wood's insecticidal properties also support its use in aqueous solutions as a natural insecticide, particularly against aphids and other sucking insects. However, it should not be sprayed on plants bearing edible leaves or fruit, as it imparts a bitter flavour that is difficult to remove.

Environmental uses

Species conservation - Over-exploitation of the tree for its wood has led the International Union for Conservation of Nature and Natural Resources (IUCN) to list it as vulnerable, highlighting the need to protect the remaining wild trees. Cultivating it in home gardens and on farms can help ease pressure on dwindling wild populations.

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

Health uses

Natural digestive aid - In parts of its native range, people brew a tea from the wood as a tonic to stimulate appetite and aid digestion. Quassin is occasionally used in laxative preparations.

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 government-run forestry departments in its native region sometimes make seedlings available free of charge to encourage planting native trees, particularly endangered ones.

Performs best in loam, sandy-loam, loamy-sand, and limestone soils that are slightly acidic to alkaline (generally pH 6.0 to 8.0), and in sites with full to partial sun.

Problem features

Birds are known to eat the fruit and disperse the seed, which germinates readily in sun or shade. This allows it 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 cause 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