Adenanthera pavonina L.

Adenanthera pavonina is a medium-sized to large deciduous tree, 6-15 m tall and up to 45 cm diameter, depending on location; generally erect; bark dark brown to greyish; inner bark soft, pale brown; crown spreading; multiple stems common, as are slightly buttressed trunks in older trees. Leaves bipinnate; 2-6 opposite pairs of pinnae, each with 8-21 leaflets on short stalks; alternate leaflets 2-2.5 x 3 cm, oval-oblong, with an asymmetric base and blunt apex, dull green on topside and blue-green underside; leaves turn yellow with age. Flowers borne in narrow spikelike racemes, 12-15 cm long, at branch ends; flowers small, creamy yellow, fragrant; each flower star shaped with 5 petals, connate at the base, and having 10 prominent stamen-bearing anthers tipped with minute glands. Pods long and narrow, 15-22 x 2 cm with slight constrictions between seeds, dark brown, turning black upon ripening, leathery, curve and twist upon dehiscence to reveal 8-12 hard-coated, showy seeds, 7.5-9 mm in diameter, lens shaped, vivid scarlet; seeds adhere to pod. Ripened pods remain on the tree for long periods, sometimes until the following spring. The name ‘Adenanthera’ is derived from a combination of the Greek words ‘aden’, a gland, and ‘anthera’, anther, alluding to the anther’s characteristics of being tipped and having a deciduous gland.

Most Adenanthera species are deciduous but are leafless for only a few days. They have been observed to be flowering and fruiting almost throughout the year, though for short intervals. Inflorescence appears at the apex of the small fruit. Seeds are probably eaten and dispersed by birds.

Found on a variety of soils from deep, well-drained to shallow and rocky, this tree prefers neutral to slightly acidic soils.

A. pavonina is a secondary forest tree favouring precipitation. Adenanthera species are found scattered in primary and secondary, evergreen to dry deciduous rainforests, but also in open savannah.

A. pavonina is endemic to southeast China and India, with 1st reports recorded in India. The tree has been introduced throughout the humid tropics. It has become naturalized in Malaysia, western and eastern Africa, and most island nations of both the Pacific and the Caribbean.

A. pavonina can be propagated from seed and the seedlings have epigeal germination. The seed coat is extremely hard and requires scarification; otherwise germination is erratic and may take up to 12 months. Manual scarification, immersing seeds in boiling water for 1 minute, or treatment with sulphuric acid has shown to significantly increase germination rates. For example, after seeds are mechanically scarified, germination rate of 100% in 1-4 days have been recorded. Following treatment, seed can be directly sown in the field or in the nursery. Germination occurs within 10 days, with young seedlings ottaining a height of 8-15 cm in approximately 3 months. Seedlings reach 20-30 cm in height in 2-3 months. Nursery stock out-plant well. Propagation from large cuttings is reported to be successful in India.

Growth is initially slow but increases rapidly after the 1st year, during which average annual growth rates of 2.3-2.6 cm in diameter and 2-2.3 m in height (recorded in American Samoa) can be attained. Trees planted 1 x 2 m apart for windbreaks and at 2 x 2 m in plantations can be thinned in 3-5 years to provide fuelwood and construction materials. For shade trees, spacing varies from 5 to 10 m, depending on the companion crop and site. Trees resprout easily, allowing for coppice management with good survival. Despite inability to suppress weeds, seedlings are hardy and can survive with minimal maintenance. The tree is susceptible to breakage in high winds, with most of the damage occurring in the crown.

A. pavonina wood is very susceptible to sapstain. The sapwood is susceptible to dry wood termites.

Seed storage behaviour is orthodox; 15% germination following 8 years open storage at room temperature; viability maintained following 3 years of hermetic storage at room temperature with 13% + or - 2% mc; 8% germination after 4 years of open storage at room temperature (Hong TD et al., 1996). There are approximately 3750 seeds/kg.

Shade or shelter: The fast growth and spreading crown of light, feathery foliage offers attractive shade. In Indonesia and Malaysia trees are planted for shade in coffee, clove and rubber plantations. It is planted along field borders as part of a windbreak. Nitrogen fixing: The legume is generally considered to be nitrogen fixing. Sparse, fast-growing, brown nodules with isolates confirmed to be Rhizobium have been observed, and Vesicular Arbuscular Mycorrhizae (VAM) have been found on the roots of nursery stock. Soil improver: The small leaves break down easily, making the species a good green manure. Ornamental: It is extensively cultivated as an ornamental for planting along roadsides and in common areas, notably for its red, glossy seeds. Intercropping: It is compatible with most tropical field and tree crops, making it suitable to use in integrated production systems. It is interplanted among field and tree crops such as spices, coffee and coconuts.

Food: Known as ‘food tree’ in Melanesia and Polynesia, the seeds of this tree are roasted over a fire and eaten by children and adults alike. Nutritional studies have shown that 1/4 of the seed weight is oil, with a high percentage of protein and a fatty acid composition, resulting in high digestibility in humans. Seeds may require boiling to neutralize toxicity. Young leaves are eaten as a vegetable. Fodder: As a supplemental source of fodder, the leaves are fairly high in digestible crude protein (17-22%) but low in mineral content. Fuel: Esteemed in the Pacific Islands for fuelwood, the wood burns readily, producing significant heat, and is used in both above- and below-ground ovens. Good-sized fuelwood, larger than 11 cm in diameter can be produced in 5 years. The wood yields very good charcoal. Timber: Adenanthera yields medium to heavy hardwood with a density of 595-1100 kg/cubic m at 15% moisture content. The heartwood is bright yellow when fresh, turning red; it is sharply demarcated from the light grey sapwood, which can be up to 5 cm wide. The heartwood is closely and even grained, with a moderately fine to slightly coarse and even texture. Wood moderately lustrous. Shrinkage is variable, and the wood seasons very well with only slight warping. The wood is very hard, durable and strong. It can be easy or somewhat difficult to work, easy to plane and it takes a high finish. The heartwood is resistant to dry wood termites. The wood is used for bridge and household construction (beams, posts, joists and rafters), flooring, paving blocks and vehicle bodies. It may also be suitable for furniture and cabinet work and turnery. Tannin or dyestuff: The red dye has been used for dyeing clothes and by the Brahmins of India for marking the forehead. Poison: Raw seeds are poisonous. Medicine: In India a decoction of young leaves is used against rheumatism and gout. Pulverized wood mixed with water is taken orally for migraines and headaches; and dysentery, diarrhoea and tonsillitis are treated with a bark and leaf decoction. Other products: The red, glossy seeds are used as toys and for necklaces, and in earlier days were used to weigh gold, silver and diamonds, because they have a narrow range in weight. The bark contains saponin and has been used to wash hair and clothing.