Common Name: Leucaena

General Information

Leucaena leucocephala is an evergreen shrub or tree with a fairly open, rounded crown; it can grow from 5 - 20 metres tall. The bole is generally short and can be 10 - 50cm in diameter[, ].
A widely used multipurpose tree in Mexico, where it provides food, medicines and a range of commodities for the local population, and is also commonly sold as a food in local and national markets, Vigorous and fast-growing, it is often cultivated in many areas of the tropics as an ornamental and is also used in reforestation and soil stabilization projects, as a shade plant for coffee etc[].
Widespread and locally abundant in Central America, this species is not believed to be under any threat[]. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The leaves of most forms of this plant contain the unusual amino acid mimosene[]. In large quantities this can be harmful[]. There are low-mimosene cultivars[].

Botanical References

Range

Central America - northern Panama, north to central Mexico.

Habitat

A ruderal weed of disturbed sites including roadsides, waste ground, areas of human activity, along the coastal fringe, including mangrove edges and frequently on and around Mayan ruins; at elevations up to 2,100 metres[].

Properties

Weed Potential	Yes
Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Growth Rate	Fast
Pollinators	Insects, Self
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Leucaena leucocephala is a plant of the tropics, it succeeds at altitudes up to 1,500 metres, occasionally to as high as 2,100 metres[]. It grows best with a mean annual temperature in the range 25 - 30°c and a mean annual rainfall of 650 - 3,000mm[]. For optimal growth it is limited to areas 15 - 25° north or south of the equator[]. It grows well only in subhumid or humid climates with moderate dry seasons of up to 6 - 7 months[].
Prefers a well-drained soil in full sun[]. Tolerant of a range of soils, including limestone, wet and dry soils, soils of volcanic origin and those with moderate levels of salt[, ]. It is found in the wild on shallow limestone soils and coastal sand[]. Prefers a pH in the range 6 - 7.7, tolerating 5 - 8.5[]. Plants are very tolerant of drought and of salt-laden winds[].
This species is an aggressive colonizer of ruderal sites and secondary or disturbed vegetation[]. This has been attributed to its precocious year-round flowering and fruiting, abundant seed production, self-fertility, hard seed coat, and ability to resprout after fire or cutting. It is now naturalized and weedy in many areas such as open (often coastal) habitats, semi-natural, disturbed, degraded habitats, other ruderal sites, and occasionally, agricultural land where it has been planted as a shade tree over cacao[].
A fast-growing and early maturing species, it can commence producing seed in its first year of growth[].
Plants are deep-rooted[].
The unripe seedpods are harvested by climbing the trees and lopping the terminal branches or groups of pods, often crudely, with machetes, small knives or cutting poles. Annual pollarding in this way apparently causes only limited damage to the trees which resprout and fruit annually[].
Plants respond well to coppicing, soon producing dense regrowth[].
Tolerates fast fires and can regrow after being burned to the crown by slower fires[].
The plant is highly susceptible to damge by Psyllids[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Young leaves, pods and flower buds - raw, steamed, in soups, with rice or mixed with chillies and other spices[]. The mid- to orange-brown seedpods are 90 - 190mm long and 13 - 21mm wide, containing 8 - 18 seeds. There can be anything from 3 - 45 seedpods per flower head, though usually 20 or less[].
Some caution is advised - see the notes above on toxicity[].

Seeds - raw or cooked. They are often eaten raw as a snack when working in the field[]. The unripe seeds are mixed with grated coconut, wrapped in banana leaves and cooked[]. They are also often used as a garnish on cooked foods or added to stews, mixed with beans and maize tortillas etc[]. The mature, but not dried, seeds are eaten raw or cooked as a delicacy[]. Dried seeds are fermented into tempeh lamtoro and dageh lamtoro[].
After removal from the pods, the unripe seeds can be dried and stored for later use or ground into a flour and mixed with wheat, corn etc[]. The seeds are 6 - 9mm long and 4 - 6mm wide; there are 15,000 - 20,000 seeds/kg[]

The dried seed can be roasted and used as a coffee substitute[, ].

An edible gum obtained from the plant is used in sauces[].

Medicinal

A decoction of the root and bark is abortifacient[].

The pods and seeds are a good tonic[].

The roasted seeds are emollient[].
The seeds have a beneficial effcct and are administered in the morning on an empty stomach. Occasionally used fresh, the torrefied seeds are more commonly prescribed in the form of a powder or sugared cakes in the treatment of ascariasis[].

The seeds contain a fatty oil, consisting of palmitic, stearic, oleic, linoleic, behenic and lignoceric acids, plus the
alkaloid leucenine (Ieucenol) 3·5%[].
The leaves yield tannin, quercitrin and alkaloids[].

Agroforestry Uses:

Leucaena leucocephala is an aggressive colonizer of disturbed ground and ruderal sites, and thus an excellent pioneer species for restoring woodland cover[]. Plants are sometimes used in re-reforestation projects[]. It is a fast growing plant with an extensive root system and has been used in land reclamation, for preventing soil erosion and as a shade plant for coffee crops[]. It thrives on steep slopes and in marginal areas with extended dry seasons, making it a prime candidate for restoring forest cover, watersheds and grasslands[].
An aggressive taproot system helps break up compacted subsoil layers, improving the penetration of moisture into the soil and decreasing surface runoff[].
Leucaena was one of the first species to be used for the production of green manure in alley-cropping systems. The leaves, even with moderate yields, contain more than enough nitrogen to sustain a maize crop[]. The finely divided leaves decompose quickly, providing a rapid, short-term influx of nutrients[]. It has even been suggested that the leaves decompose too rapidly, resulting in leaching of nutrients away from the crop-rooting zone before they are taken up by the crop[]. This also means that they have little value as mulch for weed control[]. The tree has the potential to renew soil fertility and could be particularly important in slash-and-burn cultivation, as it greatly reduces the fallow period between crops[].

Other Uses

Gum arises from the stems under ill-defined conditions of injury and disease or from sterile hybrids, especially Leucaena leucocephala x Leucaena esculenta. The gum has been analysed and found similar to gum arabic, and of potential commercial value[].

Red, brown and black dyes are extracted from the pods, leaves and bark[].

The dried seeds are widely used for ornamentation[].

The heartwood is a light reddish-brown; the sapwood pale yellow. It is medium textured, close grained. The wood is strong, hard and heavy (about 800 kg/m), of medium density. It is easily workable for a wide variety of carpentry purposes and dries without splitting or checking. Sawn timber, mine props, furniture and parquet flooring are among increasingly popular uses. However, the use of the plant for sawn timber is greatly limited by its generally small dimensions (usually not greater than 30cm diameter), its branchiness, which limits lengths of clear bole available and means wood is often knotty, and its high proportion of juvenile wood. Nevertheless, there is growing use of small-dimension sawn wood in a number of industries such as flooring, which might include this species in the future. Poles are used locally to prop bananas and as a support for yams, pepper and other vines. However, use of this species fo short-rotation production of poles is limited by their lack of durability and susceptibility to attack by termites and woodborers[].
The wood is commonly pulped for its fibre, used to make paper[]. The fibre values are similar to those of other tropical hardwoods, and it produces paper with good printability but low tearing and folding strength; the wood-pulp strength is greater than that of most hardwoods, with almost 50% greater ring crush. Its pulping properties are suitable for both paper and rayon production. Also used for particleboard production[].
An excellent firewood species with a specific gravity of 0.45-0.55 and a high calorific value of 4600 cal/kg[]. The wood burns steadily with little smoke, few sparks and produces less than 1% ash. The tree makes excellent charcoal with a heating value of 29 mJ/kg and good recovery values (25-30%)[]. Addition of the ground wood to fuel oil for diesel engines was found to involve no harmful agents in the ash[].

Propagation

Seed - pre-soak for 24 hours in warm water then sow in containers[]. Seedlings and direct sowing are recommended methods of propagation where soil-moisture conditions permit and economic weed control can be maintained. Seed pre-treatment involves soaking in hot water for 2 minutes or nicking the seed coat at the distal (cotyledon) end, using a sharp tool like scalpel, knife or nail clipper. A germination rate of 50-80% in 8 days can be achieved[].
Cuttings of semi-ripe wood. Vegetative propagation has been successful in relatively few locations, reflecting critical environmental requirements, or possibly systemic fungi. The use of bare-root cuttings has worked in Indonesia, Taiwan and Thailand[].

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