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		Nitrogen Fixing Trees Highlights (Winrock, 1990-1997, 100 p.)
			(introduction...)
			Acacia koa - Hawaii's most valued native tree
			Acacia leucophloea - shade and fodder for livestock in arid environments
			Alnus acuminata: valuable timber tree for tropical highlands
			Albizia saman: pasture improvement, shade, timber and more
			Casuarina junghuhniana: a highly adaptable tropical casuarina
			Enterolobium cyclocarpum: the ear pod tree for fasture, fodder and wood
			Erythrina variegata: more than a pretty tree
			Inga edulis: a tree for acid soils in the humid tropics
			Pithecellobium dulce - sweet and thorny
			Pterocarpus indicus - the majestic n-fixing tree
			Robinia pseudoacacia: temperate legume tree with worldwide potential
			Acacia nilotica - pioneer for dry lands
			Acacia saligna - for dryland fodder and soil stabilization
			Acacia senegal: gum tree with promise for agroforestry
			Acacia seyal - multipurpose tree of the Sahara desert
			Acacia tortilis: fodder tree for desert sands
			Alnus nepalensis: a multipurpose tree for the tropical highlands
			Casuarina equisetifolia: an old-timer with a new future
			Casuarina glauca: a hardy tree with many attributes
			Chamaecytisus palmensis: hardy, productive fodder shrub
			Dalbergia latifolia: the high-valued Indian rosewood
			Dalbergia melanoxylon: valuable wood from a neglected tree
			Erythrina edulis: multipurpose tree for the tropical highlands
			Erythrina sandwicensis - unique Hawaiian NFT
			Hippophaë rhamnoides: an NFT valued for centuries
			Leucaena diversifolia - fast growing highland NFT species
			Leucaena: an important multipurpose tree
			Olneya tesota - a potential food crop for hot arid zones
			Honey mesquite: a multipurpose tree for arid lands
			Pongamia pinnata - a nitrogen fixing tree for oilseed
			Guazuma ulmifolia: widely adapted tree for fodder and moreli
			Faidherbia albida - inverted phenology supports dryzone agroforestry
			Gleditsia triacanthos - honeylocust, widely adapted temperate zone fodder tree
			Andira inermis: more than a beautiful ornamental tree
			Erythrina poeppigiana: shade tree gains new perspectives
			Albizia procera - white siris for reforestation and agroforestry
			Albizia odoratissima - tea shade tree
			Adenanthera pavonina: an underutlized tree of the humid tropics
			Acacia mangium: an important multipurpose tree for the tropic lowlands
			Acacia auiculiformis - a multipurpose tropical wattle
			Pentaclethra microphylla: a multipurpose tree from Africa lwith potential for agroforestry in the tropics
			Myroxylon balsam and much more
			Ougeinia dalbergioides: a multipurpose tree for sub-tropical and tropical mountain regions
			Prosopis alba and prosopis chilensis: subtropical semiarid fuel and fodder trees
			Sesbania sesban: widely distributed multipurpose NFT
			Prosopis cineraria: a multipurpose tree for arid areas
			Juliflorae acacias: new food source for the sahel
			Sesbania grandiflora: NFT for beauty, food, fodder and soil improvement
			Acacia aneura - a desert fodder tree

Erythrina variegata: more than a pretty tree

Erythrina variegata is a showy, spreading tree legume with brilliant red blossoms. Commonly known as the 'Indian coral tree' in Asia or 'tropical coral' in the Pacific, this highly valued ornamental has been described as one of the gems of the floral world. It has also proven valuable for fodder production and as a sturdy component of windbreaks. It is a useful species for soil enrichment because it nodulates readily and prolifically in both acid and alkaline soils. Farmers in India appreciate E. variegata as fodder, light timber and, more recently. pulp for the paper industry.

Botany

Erythrina variegata is a medium to large tree, commonly reaching 15 to 20 m in height in 20 to 25 years. It has an erect, spreading form, typically with several vertically oriented branches emerging from the lower stem. On favorable sites, the stem can reach a diameter at breast height (dbh) of 50 to 60 cm in just 15 to 20 years.

Erythrina variegata L. From Little and Skolmen (1989), p.143.

The smooth bark is streaked with vertical lines of green, buff, grey and white. Small black prickles cover the stem and branches. These become longer if the tree suffers moisture stress. They typically drop off as the girth of the stem expands (Hegde, 1993). The leaves are trifoliate. The leaflets are commonly variegated, medium to light green, heart shaped. 7 to 12 cm wide and 12 to 18 cm long. The trees are deciduous. typically losing their leaves before flowering except under very humid conditions.

Brilliant orange-red flowers emerge in dense, conical inflorescences 5 to 7 cm long and 2 to 3 cm wide, usually after the leaves have dropped. Flowering is normally followed by a lavish production of seed. The pods are thick and black-1.5 to 2 cm wide and 15 to 20 cm long. Each contains 5 to 10 egg-shaped seeds. These are glossy brown, red or purple and are 6 to 10 mm in diameter and 12 to 17 mm long.

A column-shaped cultivar, 'Tropic Coral' or 'Tall Erythrina', is used extensively in windbreaks and as an ornamental in parks and gardens. Through cultivation, it has spread from New Caledonia to Australia, Hawaii and southern Florida. Unlike other cultivars. the leaves of 'Tropic Canal' remain on the tree through flowering.

Ecology

Erythrina variegata is well adapted to the humid and semiarid tropics and subtropics, occurring in zones with annual rainfall of 800 to 1500 mm distributed over a five- to six-month rainy season. The species is most commonly found in warm coastal areas up to an elevation of 1500 m. The trees prefer a deep. well-drained, sandy loam, but they tolerate a wide range of soil conditions-from sands to clays of pH 4.5 to 8.0. They can withstand waterlogging for up to two weeks and are fairly tolerant of fire. Erythrina variegata is bird-pollinated, outcrossed and sometimes genetically incompatible.

Distribution

Erythrina variegata is native to the coast of India and Malaysia. It has been widely introduced in coastal areas of the Old World tropics, extending from East Africa and Madagascar through India, Indochina, Malaysia, northern Australia and Polynesia. The seeds can float on salt water for months, facilitating the spread of the species. Introduced to the Americas, it was so well established by 1825 that Candolle described two new species based on trees considered to be native to the New World (McClintock, 1982). It is now a very popular hedge species in southern Florida.

Uses

Support for vine crops.

Farmers in India use E. variegata to support climbing plants such as betel (Piper belle), black pepper (Piper nigrum), vanilla (Vanilla planifolia) and yam (Dioscorea spp.) (Hegde, 1993). Trees established to support vines are usually planted at a spacing of 2 x 2 to 2 x 3 m. Vines are planted three to four months after establishment of the tree seedlings or during the following rainy season. During the hottest months. foliage from the closely spaced trees shades the vines and keeps them moist. When the days become cooler, the leaves fall and the vines receive more direct sunlight, which matches their requirements at this time.

Shade.

Coffee and cacao growers establish E. variegata shade trees from large cuttings (2 to 3 m long and 2 to 5 cm in diameter) at a spacing of 8 x 10 m. The trees are pollarded once a year to a height of 2 to 3 m to produce a spreading crown. The pruned leaves are usually spread in the plantation as mulch. The branches may be used as fuelwood.

Windbreaks.

Erythrina variegata, particularly the columnar variety, is widely used as a windbreak for soil and water conservation. The trees have a strong, vertical root system that does not seem to compete too severely with adjacent crops (Rotar et al., 1986). Windbreaks are normally established from large cuttings planted in lines at a spacing of about 2 m.

Live fenceposts.

Erythrina variegata makes excellent live fenceposts. Farmers commonly establish fenceposts from three-yearold upright branches about 15 cm in diameter and 2.5 m long. These are normally stacked in the shade in an upright position and left to cure for one week before planting.

Fodder.

The foliage of E. variegata makes an excellent feed for most livestock. Leaves normally contain 16 to 18% crude protein and have an in-vitro dry-matter digestibility of 50% A tree of average size, pruned three or four times a year, produces from 15 to 50 kg of green fodder annually depending on growing conditions. Trees maintained in coffee plantations benefit from associated cultivation practices-they can produce up to 100 kg of fodder from one annual harvest. The leaves have no known toxicity to cattle.

Wood.

The wood of E variegata is light and sott. with a specific gravity of 0.2 to 0.3. Each shade tree in a coffee plantation can yield from 25 to 40 kg of wood from annual pollarding. The wood is used to construct floats, packing boxes, picture frames and toys, and, in India, it is increasingly used for pulp production. The timber requires careful seasoning, preferably kiln drying. It does not split on nailing, but holds nails poorly.

Medicinal.

Erythrina variegata has a reputation for medicinal properties in India, China and Southeast Asia. The bark and leaves are used in many traditional medicines, including paribhadra, an Indian preparation said to destroy pathogenic parasites and relieve joint pain. Juice from the leaves is mixed with honey and ingested to kill tapeworm, roundworm and threadworm (Hegde, 1993). Women take this juice to stimulate lactation and menstruation. It is also commonly mixed with castor oil to cure dysentery. A warm poultice of the leaves is applied externally to relieve rheumatic joints. The bark is used as a laxative, diuretic and expectorant.

Other uses.

With their rapid growth and prolific nodulation, all erythrinas are a good source of organic matter for green manure. The nitrogen-rich litterfall decomposes rapidly, making nutrients available for plant uptake. The dry foliage of E. variegata normally contains from 1 to 3% nitrogen.

Aqueous leaf extracts of E. variegata have also proven highly toxic to certain nematodes (Mohanty and Das, 1988).

Silviculture

Establishment.

Erythrina variegata is successfully propagated from seed or large stem cuttings. Seed should be scarified by soaking in hot water (80°C) for 10 minutes and then in tepid water overnight. Treated seeds normally germinate within 8 to 10 days. Well-watered seedlings are normally ready for planting at 10 weeks.

Woody cuttings establish best under dry conditions. They should always be held for at least 24 hours before planting to prevent attack by soil fungi. Cuttings establish quickly, producing axillary shoots in three to four weeks and then rooting. To produce tall trees with straight stems, it is important to retain the terminal bud of branch cuttings. The columnshaped form, 'Tropic Coral', may not reproduce true to form from seed and should thus be propagated from cuttings.

Management.

Erythrina variegata generally requires little maintenance. Once established, seedlings grow rapidly, usually to 3 m in one year. Cuttings typically produce more and larger side branches than seedlings; they should be pruned when young if upward growth and a clear bole are desired.

Limitations

This species is a host to the fruit-piercing moth Othreis fullonia, a destructive insect pest in the Pacific region. The larvae feed on the tree and the adults 'pierce' important commercial fruits such as oranges, guava, papaya. banana and grapes. causmg serious economic losses (Muniappan, 1993). The light wood. with 60 to 65% moisture content, is not useful as a fuel. Even when dry, it produces smoke when burned.