A widely planted multipurpose tree from tropical America introduced to most of the tropics. Forms monotypic stands in dry lowland areas of oceanic islands and regenerate freely in most of the tropics.
Deciduous tree usually growing to 9 m and in places up to 18 m high.
Two subspecies of L. leucocephala, leucocephala and glabrata, are recognized. The former is shrubby. The species is evergreen when moisture is not limiting.
Globular flower heads contain numerous tiny hermaphrodite white flowers. Largely self-fertilised and self-compatible but hybridization with other species of the genus occurs readily. The 18 cm long pods contain about 20 seeds (size: ca 7 x 3 mm) and are borne in clusters of around 20. Germination rates vary from 5% to 90%. Flowering starts within a year of germination and after two years trees produce fruits all year round. Flowering increases under moisture stress or with the onset of shorter days in the sub-tropics. In India there are two flowering and fruiting seasons with a period of around four months separating flowering from pod dehiscence.
Leaves are shed as a result of light frosts and after a heavy frost all above ground growth will die but the crown will survive and sprout vigorously the following year. Some Mexican provenances appear to be more frost tolerant. Stem and crown cuttings root and tree coppices well when cut and after fire. This very deep-rooted species fixes nitrogen and is drought tolerant even at the young seedling stage.
L. leucocephala has moderate tolerance for shade as it can regenerate under its own canopy and under Lantana camara.
It is used as a shade plant in coffee, rubber, cacao and cinchona plantations, for reforestation, windbreaks and firebreaks. Necklaces are made with the seeds.
The extent of its range is uncertain but it is native to Mexico and probably to Central America and West Indies. The origin of this tetraploid species is unknown.
The climate is seasonal with a 3-6 month dry season and a rainfall of 750-1800 mm. The altitudinal range is the main difference between subspecies leucocephala and glabrata. They grow from sea level to, respectively, 500 and 1500 m.
It forms thickets in dry limestone and dry coastal regions of Puerto Rico.
In Puerto Rico commonly found along roadsides and abandoned pasture.
Several pests and diseases affect L. leucocephala including a leaf spot disease Camptomeris leucaenae.
Extensively planted worldwide and presently covering up to 5 million ha. Until the end of the 19th century all introductions were of the shrubby type but subpecies glabrata has been widely introduced over the past three decades. Introduced to the Pacific islands by the Spanish who over 400 years ago transported L. leucocephala feed and seeds to the Philippines. Introduced to Hawaii in 1864 and to the Marquesas Islands prior to 1893. It is now common in the lowlands of many Pacific islands often forming monotypic stands. In India it is thought to be a weed with tremendous natural regeneration.
L. leucocephala invades cleared areas and forms dense thickets. In the Hawaiian islands it sometimes becomes the dominant part of the vegetation at low altitude (0 - 300 m) on dry and disturbed sites. In the Marquesas Islands the tree is spreading into native disturbed forest. Plant growth is very variable. In poor conditions it is vulnerable to weed competition and wildlife. In India the tree spread into fallows within a few years of planting although no regeneration was recorded beyond a distance of 40 m. The species was reported to be abundant soon after its introduction to Hawai'i. During the 1980s crown dieback observed in many parts of Hawai'i it appears that trees with an understorey of shallow rooted naturalised succulents suffered from less dieback and were more vigorous than with a grassy understorey. The differing water requirements between the succulents and the grasses may explain these observations.
In Hawai'i it is naturalised at sites which receive only 300 mm rain per year. Under cultivation it performs well in regions with a mean annual rainfall ranging from 650 to 3000 mm. Grows on a wide variety of soils.
Lowland vegetation on many Pacific Islands is now almost entirely dominated by introduced species. On the Marquesas Islands the dry lowland forests contain 28 woody species of which 9 are aliens. The lowland vegetation of Hawai'i has been much altered and is now dominated by exotics.
In Hawai'i an introduced beetle larvae destroys seeds and nearly all pods are infested. Since 1983, the psyllid Heteropsylla cubana from Cuba has been rapidly spreading westward throughout the Pacific and tropical Asia. Particularly in dry regions it results in total defoliation, death of terminal shoots and inhibits flowering, and repeated attacks result in tree death.
Although the impact of L. leucocephala on the invaded ecosystem has not been reported in much detail, it is clear that the tree, as well as other introduced species, displaces the native lowland vegetation of Pacific islands. Under a L. leucocephala canopy, which is relatively open, the soil is often free of vegetation.
Once considered as the 'miracle tree' because of the variety of uses, including, firewood, timber, human food, green manure, shade, erosion control and forage. However both the foliage, high in protein and vitamin A, and the edible seeds contain the toxic amino acid mimosine and therefore can be toxic in large quantities. Horses, feeding on the tree, lose their hairs. In the Marquesas Islands farmers consider the species as an agricultural weed which is nearly impossible to uproot completely.
A clear conflict of interest between the agroforestry value of the tree and its deleterious environmental impact can be seen in the practitioners attitude towards the psyllid Heteropsylla cubana. Agroforestry has suffered from serious economic losses, in Java estimated at $ 2.8 million between 1986 and 1988 as a result of the pest and biological control programme of the insect have been initiated. On the other hand managers of some Pacific islands, where L. leucocephala is considered a weed, would consider the arrival of the psyllid as beneficial. In western Africa the tree grows freely both from seed and cuttings, the plant becomes a pest difficult to eradicate from cultivated land.
L. leucocephala and other woody invaders of lowland dry vegetation of oceanic islands probably have some, as yet undetermined, competitive advantage over native species and/or native species lack the characteristics necessary to cope with high levels of human disturbance.
No differences have been reported.