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leucaena--1
FabaceaeCPea family
Leucaena leucocephala (Lam.) de Wit.
leucaena
C. D. Whitesell and John A. Parrotta
Dr. Whitesell retired from the USDA Forest Service; Dr. Parrotta is a research forester at the
USDA Forest Service=s International Institute of Tropical Forestry, Río Piedras, Puerto Rico.
Other common names. leadtree, zarcilla, popinac, koa haole.
Synonyms. Leucaena glauca (L.) Benth., L. blancii Goyena, L. glabrata Rose, L. greggii
Watson, L. latisiliqua (L.) W.T. Gillis, L. salvadorensis Standl.
Growth habit, occurrence, and use. The genus Leucaena includes about 50 species of trees
and shrubs that are native to Central America and southeast Asia. Leaves, legumes (pods), and young
seeds of at least 4 Leucaena species have been used by humans for food since the time of the Mayans
(Brewbaker and others 1970). LeucaenaCLeucaena leucocephala (Lam.) de Wit.Cthe most
widespread member of the genus, originated in Mexico and Central America (Brewbaker and others
1972) but is now considered pantropical. It is found throughout the West Indies from the Bahamas
and Cuba to Trinidad and Tobago and has become naturalized in southern Texas and southern
Florida; it also has been planted in California (Little and Wadsworth 1964). The species was
introduced to Puerto Rico and the Pacific Islands during the Spanish colonial era. It was introduced
to Hawaii about 1864. It invades cleared areas and forms dense thickets, either as a shrub or small
tree up to 10 m in height (Takahashi and Ripperton 1949). This species is evergreen when moisture
is not a limiting factor. Strains of leucaena can be categorized as one of two types: the Acommon@ (or
AHawaiian@) and the Agiant@ (or ASalvadorian@) (Brewbaker and others 1972). The common type,
representing the strains most commonly naturalized outside of the species= native range, is a
drought-tolerant, branchy, abundantly flowering, and aggressive shrub or small tree. The
Salvadorian type is an erect tree that attains heights up to 20 m (Brewbaker and others 1972; NAS
1984). In many parts of the world, the species is considered a weed.
Leucaena is used for a variety of purposes, including timber, fuelwood, forage, and organic
fertilizer. It is planted as a shade tree for coffee, cacao, and other cash crops; for soil fertility
improvement; erosion control; and site preparation in reforestation (Neal 1965; NAS 1984; Parrotta
1992; Whitesell 1974). The light reddish heartwood is easily worked but is of low to medium
durability. It is used for light construction, boxes, and particleboard. The wood is considered a
promising source of short-fiber pulp for paper production. The protein-rich leaves and legumes are
widely used as fodder for cattle, water buffalo, and goats. The protein content of dry forage ranges
from 14.0 to 16.2% (Oaks and Skov 1967). Depending on variety, the protein consists of 19 to
47% mimosine (Brewbaker and others 1972), an amino acid that can cause weight loss and ill
leucaena--2
health in monogastric animals such as pigs, horses, rabbits, and poultry when leucaena fodder
comprises more than 5 to 10% (by weight) of the diet. Ruminants (cows, buffalo, and goats) in
most parts of the world (except for Australia, Papua New Guinea, and parts of Africa and the
Pacific) have stomach microorganisms that render mimosine harmless.
Flowering and fruiting. Flowering phenology varies widely among varieties and with
location. The common type varieties flower year-round, often beginning as early as 4 to 6 months
after seed germination. The giant varieties flower seasonally, usually twice a year. The spherical,
whitish flower heads are 2.0 to 2.5 cm in diameter and are borne on stalks 2 to 3 cm long at the
ends or sides of twigs (Parrotta 1992). The fruits, generally produced in abundance from the first
year onward, are flat, thin legumes that are dark brown when ripe; they measure 10 to 15 cm long
and 1.5 to 2.0 cm wide. A legume contains 15 to 20 seeds (Parrotta 1992). The seeds are small (8
mm long), flat, teardrop-shaped, shiny, and dark brown with a thin but fairly durable seedcoat. The
seeds are usually released from dehiscent legumes while still on the tree, although unopened or
partially opened legumes may be carried some distance by wind. The legumes are commonly eaten
by and pass through the digestive tracts of livestock, which appear to be important dispersal agents
in pastures.
Collection, extraction, and storage. Legumes may be collected from branches when ripe,
before dehiscence; they should be sun-dried and then threshed to release seeds. Threshing is
commonly done by beating the dried legumes in cloth bags. There are about 17,000 to 24,000 clean
seeds/kg (11,000/lb) (Parrotta 1992). Unscarified seeds will remain viable for more than 1 year
when stored under dry conditions at ambient temperatures and up to 5 years stored at 2 to 6 ºC.
Dried, scarified seeds will remain viable for 6 to 12 months (van den Beldt and others 1985;
Daguma and others 1988; Parrotta 1992).
In Hawaii the larvae of a recently introduced beetleCAraecerus levipennis JordanCcan
destroy the seed. At times, virtually all of the legumes in certain stands are infested (Sherman and
Tamashiro 1956). Seeds should be fumigated as soon as possible after collection to kill the larvae.
Fumigation is accomplished by exposing the seeds to methyl bromide at a concentration of 32 g/m3
(0.032 oz/ft3) for 2 hours at 27 ºC.
Pregermination treatments. Although seeds may be sown without scarification,
mechanical scarification (abrasion with sandpaper or clipping the seedcoat) or either of the following
2 treatments are used to ensure more rapid and uniform germination (Parrotta 1992): (a) immersion
in hot water (80 ºC) for 3 to 4 minutes followed by soaking in water at room tmperature for up to
12 hours or (b) soaking in concentrated sulfuric acid for 15 to 30 minutes. Scarification may be
followed by inoculation with nitrogen-fixing Rhizobium bacteria (mixed with finely ground peat)
after coating the seeds with a gum arabic or concentrated sugar solution. Presowing inoculation of
seeds facilitates good field establishment in soil devoid of effective rhizobia strains.
Germination tests. Germination rates are commonly 50 to 98% for fresh seeds (Daguma
and others 1988; NAS 1984). Scarified seeds germinate 6 to 10 days after sowing; unscarified seeds
germinate 6 to 60 days after sowing (Parrotta 1992). Germination in leucaena is epigeal.
Nursery practice. Leucaena seeds germinate on or near the soil surface and should not be
planted deeper than 2 cm (: in). Nursery media should be well-drained, have good nutrient and
leucaena--3
water-holding capacity, and have a pH between 5.5 and 7.5 (van der Beldt and Brewbaker 1985).
Light shade is recommended during the first few weeks of seeding development, and full sun
thereafter (Parrotta 1992). Taproot development is rapid in young seedlings. Seedlings generally
reach plantable size (height of 20 cm or 8 in) in 2 to 3 months. Plantations may be established by
direct seeding (Francis 1993); by planting container seedlings, bareroot seedlings, stem cuttings (2 to
5 cm in diameter).
Literature Cited
Brewbaker JL, Plucknett DL, Gonzales V. 1972. Varietal trials of Leucaena leucocephala (Akoa
haole@) in Hawaii. Res. Bull. 166. Honolulu: University of Hawaii, College of Agriculture,
Hawaii Agricultural Experiment Station. 29 p.
Daguma B, Kang BT, Okali DUU. 1988. Factors affecting germination of leucaena (Leucaena
leucocephala (Lam.) de Wit. seed. Seed Science and Technology 16(2): 489B500.
Francis JK. 1993. Leucaena leucocephala established by direst seeding in prepared seed spots under
difficult conditions. Nitrogen Fixing Tree Reports 11: 91B93.
Little EL Jr, Wadsworth FH. 1964. Common trees of Puerto Rico and the Virgin Islands. Agric.
Handbk. 249. Washington, DC: USDA Forest Service. 548 p.
NAS [National Academy of Sciences]. 1984. Leucaena: promising forage and tree crop for the
tropics. 2nd ed. Washington, DC: National Academy of Sciences. 100 p.
Neal MC. 1965. In gardens of Hawaii. Special Publ. 50. Honolulu: Bishop Museum Press. 924
p.
Oaks AJ, Skov O. 1967. Yield trials of Leucaena in the US Virgin Islands. Journal of Agriculture of
the University of Puerto Rico 51: 176B181.
Parrotta JA. 1992. Leucaena leucocephala (Lam.) de Wit: leucaena, tantan. Res. Note SO-ITF-
SM-52. New Orleans: USDA Forest Service, Southern Forest Experiment Station. 8 p.
Sherman M, Tamashiro M. 1956. Biological control of Araecerus levipennis Jordan (Coleoptera:
Anthribidae). Proceedings of the Hawaii Entomological Society 16: 138B148.
Takahashi M, Ripperton JC. 1949. Koa haole (Leucaena glauca): its establishment, culture, and
utilization as a forage crop. Res. Bull. 100. Honolulu: University of Hawaii, College of
Agriculture. Hawaii Agricultural Experiment Station. 56 p.
Van den Beldt RJ, Brewbaker JL, eds. 1985. Leucaena wood production and use. Waimanalo, HI:
Nitrogen Fixing Tree Association. 50 p.
Whitesell CD. 1974. Leucaena leucocephala, leucaena. In: Schopmeyer CS, tech. coord. Seeds of
woody plants in the United States. Agric. Handbk. 450. Washington, DC: USDA Forest
Service: 491B493.
leucaena--4
Figure 1CLeucaena leucocephala, leucaena: seed, × 4.
Figure 2CLeucaena leucocephala, leucaena: longitudinal section through a seed, × 12.
