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Leucaena leucocephala

Accession Count: 0
Common Name: white lead tree
Family Name: Fabaceae
Botanical Name: Leucaena leucocephala
Synonyms:
Botanical Synonyms: Leucaena glauca, Mimosa leucocephala
Sub Species:
Variety:
Forma:
Cultivar:
Characteristics: Leucaena leucocephala is a large shrub or small to
medium-sized tree that generally grows up to 25 feet tall, but can reach 60
feet under the right conditions (1,2,3) . The fast-growing plant exhibits an
open, spreading habit with a trunk diameter between 4 and 10 inches. It has
also smooth grey-brown bark with conspicuous pores called lenticels  (1,4,5,6). The alternate, bipinnate leaves,
measuring 10-12 inches long, are divided into 4-9 pairs of lateral pinnae (main
divisions). The leaves have an opposite phyllotaxis and are composed of 10-20
pairs of oblong or lanceolate grey-green leaflets ⅜ to ¾ inches long and ⅛ inch
wide (1,5,7,8). Fragrant white or pale yellow puffballs, measuring ½ to 1 inch
in diameter and made up of 100-180 tiny flowers, appear on short stems in
axillary clusters at the ends or sides of branches (3,5,6,7,8,9,10). Each
puffball produces 6-20 flat, thin seedpods, 4-6 inches long, which are initially
green and mature to a papery reddish-brown, eventually splitting along both
edges (1,3,5,7,8,9,11). The flowers, a good source of pollen for bees, are
self-fertile and most seedpods arise from self-pollination (3,9,10). Seedpods take
about 10-15 weeks to ripen and contain around 20 glossy brown, hard, flat, oval
seeds (3,7,11). In nature, seeds are spread by rodents, birds, or cattle (2,9).
In warm climates, the plant flowers and fruits year-round. Flowers and pods in
varying stages of maturity can often be found on the same tree (3,5,9,10). In
Arizona flowering usually occurs in the spring with fruiting in the summer and
fall (6). The plant’s wood is weak and brittle, with yellow sapwood and brown heartwood
that is hard and heavy (3,5,6,10). Leucaena leucocephala is a
deep-rooted species, having extensive taproot and lateral root systems. The
roots are important for fixing nitrogen in the soil by forming root nodules
when Rhizobium species are present (3,10). 
Compound: Leu leu
Geographic Origin: Mexican Tropics
Ecozone Origin: Neotropic
Biome Origin:
Natural History: Leucaena leucocephala’s original range included parts of Mexico and Central America and may have extended as far north as Texas, but human actions have made its exact range unknown (2,6,7,8,9,10,11,12,13,14). The original Nahuatl word for the plant, huaxin, still survives today in the Spanish name for the plant, guaje, and in the name of the Mexican state Oaxaca, which reportedly means “place where the leucaena grows” (10,14). The Spanish explorers of the New World recognized the plant’s usefulness as animal fodder and carried it to the Philippines from where it spread to other parts of the world (2,13,15). In the U.S. it was first introduced to Hawaii in 1864 and later on the mainland to Florida and Texas to be used for erosion control, land reclamation, and animal feed (7,9). Today the plant has become naturalized throughout the tropics and can be found in both the eastern and western hemispheres (1,5,10,13,14,16). It is considered invasive in many areas, including Florida where it is considered a Category II invasive species and is on the state’s list of noxious weeds, making it illegal to plant (2,7,8). On Ascension Island Leucaena leucocephala, together with other invasive plant species, may have contributed to the extinction of a native plant called Oldenlandia adscensionis (2,17). It is considered by the International Union for the Conservation of Nature (IUNC) to be among the 100 Worst Invasive Alien Species on the planet (17). There are three recognized subspecies: leucocephala, glabrata, and ixtahuacana (3). The genus name, Leucaena, appears to derive from the Greek verb leukainein and means “to become white,” perhaps referring to the plant’s appearance when in flower (15). The specific name leucocephala comes from two Greek words, leukos, meaning “white,” and cephale, meaning “head,” referring to the plant’s flowers (3,15). 
Cultivation Notes: Leucaena leucocephala is an aggressive grower that is found throughout tropical and subtropical climates, mainly within 25° latitude of the equator (1,3,5,10,12). The plant habitat includes areas from sea level to 5000 feet above sea level where mean annual temperatures average between 75° and 85° F and rainfall measures between 25 and 120 inches annually  (3,13). Seeds are the most effective means of reproduction, although they often need some type of scarification to germinate. The plant can also be propagated from cuttings (1,4,5,6,8,9,10,13). It requires warm temperatures for optimal growth and does best in full sun (1). Exposure to light frost will kill the leaves; heavy frost will kill the plant to the ground (3,4,8,13). The plant, however, is very tolerant of defoliation and quickly responds with generous regrowth to damage caused by frost, fires, foraging, or coppicing (3,4,8,9). It is very drought tolerant, folding its leaves during dry spells to prevent water loss, and will drop its leaves under severe conditions (1,10,13,14). The plant is tolerant of most soils as long as they are well-drained (4,10,11,13). It prefers alkaline conditions, but can tolerate pH anywhere between 5.2 and 8.5; it does not tolerate high salinity or waterlogging (4,10). It readily invades disturbed ground and can form monospecific thickets, threatening native plant communities (3,7,9,10). Because the plant is very aggressive and can escape cultivation easily, it is not advisable that it be planted in regions where it does not already exist (6,10). To reduce spread of the plant, the canopy base should be elevated and any seedlings should be rogued (6). 
Ethnobotany:
In the 1970s and 1980s Leucaena leucocephala was called a “miracle tree” because of the wide range of applications in which it could be used (13). Its main use is as fodder for animals. Its leaves are very digestible and nutritious for ruminant animals, rivaling or exceeding alfalfa in nutritive value, and can be eaten mature or immature, grazed or harvested, fresh or dried (1,3,10,12,13,14,16). Its consumption, however, it should be limited, especially for non-ruminant animals and poultry, due to the presence of the toxic amino acid mimosine that is found in the leaves and seeds (1,2,11,13,14,16). In large amounts, mimosine can cause hair loss, thyroid problems, and other conditions in non-ruminants (and humans); ruminants, however, such as cows, sheep and goats can tolerate higher amounts in their diets if they have a specific bacterium in their rumen to digest it (1,2,4,10,11,13,14,15,16). Ruminants that do not have this bacterium can be “inoculated” with it to allow them to consume more of the plant in their diets (4,13,14,15,16) Young pods and seeds have been eaten raw for centuries by indigenous tribes in Mexico and Central America, although the presence of mimosine limits their consumption (4,12,13,15,). However, cooking the pods, ripe or immature, removes much of the mimosine and allows them to be consumed as a vegetable (10,14,15). Ripe seeds are parched and eaten as a snack like popcorn or ground and used as a substitute for coffee (1,3,10,12,14,15). Seedpods and young shoots are used in a variety of dishes in Asian cuisine (16). Because of its ability to fix large amounts of nitrogen in the soil, the plant has been used as green manure in agricultural settings and has had applications in agroforestry (1,4,10,11,13,16). It was one of the first plants to be used in formal alley farming and remains the most commonly researched species for that purpose, usually having only positive effects on nearby plants (1,3,4,13,16). Its value in preventing erosion, in soil improvement and in land reclamation is frequently cited (1,3,4,10,11,13,16). It is often used as a companion plant, providing shade for standing crops such as bananas, cocoa, and coffee, or support for vine-climbers like black pepper, passionfruit, and vanilla (1,3,4,11,13,15). It can be used as an ornamental plant or closely planted as a windbreak or trimmed as a hedge or living fence (1,3,7,10,13,16). The wood of the plant is used as firewood and to make posts, furniture, flooring, wood pulp, particle board, and charcoal (1,3,5,10,11,12,14,16,). The gum is sometimes used as a substitute for gum arabic (1,3,12,13,). The hard seeds are strung together to make jewelry, purses, placemats and other items (1,5,10,11,12,14,). In some countries, the seeds are considered to have magical powers and are used as prayer beads and rosaries (12). Red, brown and black dyes can be obtained from the pods, leaves and bark (3). Experimental attempts have been made in using the toxins in the plant as fungicides or insecticides or as a depilatory for shearing sheep (1,14). The plant has been used in folk medicine a variety of purposes. The bark is taken to relieve internal pain (1). An infusion of the bark and root have been used as an emetic, contraceptive, emmenagogue, ecbolic, abortifacient or depilatory (1,10,12). The bark and root can also be used topically to eliminate lice and flea infestations (12). The plant has been used as a purgative, vermifuge, or emollient (12). The oil from the seeds is reputed to have therapeutic value (12).
Height: 20 - 50 feet
Width: 16 - 20 feet
Growth Rate: Fast Growing
Grow Season: Summer
Flower Season: Spring
Color: White
Function: Shade
Spread: Spreading
Allergen: Non-allergenic
Invasive: Invasive
Toxicity: Toxic
Hardy: Tender
Water Use: Low water Use
Citations:
1. Duke, J. (1983). “Leucaena leucocephala,” in Handbook of Energy Crops (unpublished). Center for New Crops & Crop Products, Purdue University. Accessed June 03, 2015.

2. “Lead Tree.” Wild South Florida. Accessed June 03, 2015.

3. “Leucaena leucocephala.” World Agroforestry Centre. Accessed June 03, 2015.

4. “Leucaena leucocephala.” Tropical Forages. Accessed June 03, 2015.

5. Little, E. and Skolmen, R. (1989) “Koa haole, leucaena.” Forest Service, U.S. Department of Agriculture, reprinted by College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Accessed June 03, 2015. 

6. “Leucaena leucocephala (lead tree).” Virtual Library of Phoenix Landscape Plants, Arizona State University. Accessed June 03, 2015.

7. “Lead Tree.” Center for Invasive and Aquatic Plants, University of Florida, IFAS Extension. Accessed June 03, 2015.

8. “August 2009: Leucaena leucocephala, Lead Tree.” Weed of the Month, Florida Department of Agriculture and Consumer Services. Accessed June 03, 2015.

9. “Leucaena leucocephala.” Texas Invasives. Accessed June 03, 2015.

10. Francis, J. “Leucaena leucocephala (Lam.) de Wit.” U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry. Accessed June 03, 2015.

11. “Leucaena leucocephala – White Leadtree.” Hawaiian Plants and Tropical Flowers. Accessed June 03, 2015.

12. “Lead Tree.” Herbs info. Accessed June 03, 2015.

13. Shelton, H. and Brewbaker, J. “Leucaena leucocephala – The Most Widely Used Forage Tree Legume.” Food and Agriculture Organization of the United Nations.  Accessed June 03, 2015.

14. Brewbaker, J. (1995). “Leucaena.” Center for New Crops and Plant Products, Purdue University. Accessed June 03, 2015.

15. Deane, G. “Jumbie Bean, White Lead Tree.” Eat the Weeds and other things too. Accessed June 03, 2015.

16. “Leucaena leucocephala (leucaena).” Invasive Species Compendium, CABI. Accessed June 03, 2015.

17. “Leucaena leucocephala (tree).” Global Invasive Species Database 
(http://www.issg.org/database). Accessed June 03, 2015.

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Leucaena leucocephala