Description and distribution

Gliricidia is a genus of six to nine species of small, spreading, unarmed, fast-growing perennial shrubs or short-boled trees, reaching 5-15 m in height. They are able to fix nitrogen and nodulation has been observed and evaluated (Patil and Prasunamma, 1986). They nodulate readily, usually within three months of planting when grown from stakes, or even faster when established from seed (Chadhokar, 1982). They are deciduous, glabrous and characterized by a spreading or pyramidal crown of foliage borne on long, irregular, feathery branches that often curve downwards. They seasonally bear numerous large, showy, pink to light purplish, pea-shaped flowers which often appear before the leaves at the end of the dry season. The pods are glabrous, blackish at maturity and measure up to 14 cm long and 1.5 cm wide (Smith and van Houtert, 1987).

Native to tropical America and the West Indies, Gliricidia species now enjoy worldwide distribution as multipurpose trees suitable for use as living fences, for shade and soil improvement, as fuel wood and pole material, and as sources of high-protein fodder and browse. Gliricidia establishes well in the tropics: it is found in lowlands and at altitudes of up to 2000 m. Although it is best suited to the wetter areas in the humid tropics where it is widely cultivated, it is native to the drier parts of Central America. Its considerable drought tolerance is due to a policy of avoidance, since it drops its leaves and becomes dormant during the driest parts of the year. The plant thrives on relatively acid, infertile soils and shows some tolerance of short-term waterlogging, conditions which are unsuitable for some of the other popular tree legumes such as Leucaena leucocephala (Chadhokar, 1982).

Most published data on Gliricidia refer to G. sepiura, or to G. maculata. There is some confusion in the literature regarding the taxonomy, since authors such as Allen and Allen (1981) consider these taxa to be synonymous, while Wiersum and Dirdjosoemarto (1987) regard them as separate species. NFTA (1989) describes G. maculata as being native to the Yucatan Peninsula and having white flowers, rounded leaflets and relatively small pods and seeds. In contrast, G. sepium is considered to be native to the Pacific coast of Mexico and Central America and has pale coloured flowers, more pointed leaves and larger seeds and pods. G. ehrenbergii comes from highland areas with altitudes of 1500-2000 m. It is a shrub growing to 3 m in height, with deep red-to-purple flowers and small rounded leaflets. This review will concentrate on G. sepium and G. maculata, although most published reports probably refer to the same species, due to taxonomic confusion.

Because of the ease with which the species may be vegetatively propagated, it is likely that most of the work carried out in a number of distinct countries has concentrated on a narrow gene base.