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Small trees along terrace boundaries: Trees to about 5m height, cultivated along terrace boundaries, Oaxaca, Mexico. |
Local names:
Spanish (guaje delgado)
Leucaena pallida is a small deciduous multiple-stemmed tree 3-7 m tall although occasionally to 10 m tall and a bole diameter of 10-15 (-30) cm, with an open, spreading or narrow crown. Bark smooth, metallic-grey, blotched lighter grey with horizontally aligned pale brown lenticels, slash greenish. Leaves have 15-27 pairs of pinnae, pinnular rachis 8-11 cm long, sparsely hairy, leaflets 6-8(-10) mm long, 1-2 mm wide, 39-50 pairs per pinna, asymmetric truncate at base, linear or oblong, acuminate at apex. Petiole gland unstalked, shallow crater-shaped, elliptical, 3-4 mm long by 2-3 mm wide. Flower head 14-16 mm in diameter, 95-110 flowers per head, in groups of 3-5 in leaf axils on actively growing shoots, sometimes with suppression of leaves on the flowering shoot, flowers appear pale pink or dull purplish mauve. Pods 12-19 cm long, 14-18 mm wide, 3-5 per flower head, linear, slightly thickened and leathery, glossy maroon when unripe, turning reddish-brown, glabrous or occasionally hairy. Seed 5-7 mm wide, 6-8 mm long, slightly rhombic aligned transversely in pods. The specific epithet means pale in reference to the flowers.
Ecology
It is mainly found in the mid interior highlands of south central Mexico on shallow calcareous soils, in disturbed dry thorn forest, dry mattoral, oak forest, oak-pine forest and particularly in the oak-dry thorn forest transition zone. It is moderately frost tolerant and withstands 5-7 months dry season in its native range where rainfall is highly seasonal.
Native range
Mexico
Tree management
The tree coppices well producing few seeds. Silvicultural practice should include dense planting (10 000 stems/ha) with thinning for fuelwood at one and three years, and harvest after 6-8 years. Trees are lopped annually during pod harvesting.
There are between 20 000-25 000 seeds/kg. Seeds can be stored for a long time if stored at <=4 deg. C and <10 % moisture content following conventional seed storage methods.
It is mainly found in the mid interior highlands of south central Mexico on shallow calcareous soils, in disturbed dry thorn forest, dry mattoral, oak forest, oak-pine forest and particularly in the oak-dry thorn forest transition zone. It is moderately frost tolerant and withstands 5-7 months dry season in its native range where rainfall is highly seasonal.
L. pallida is mainly propagated by seed. Seeds require pretreatment to break the hard seed coat and the most reliable method is manual scarification. A second method of producing seedless leucaena exploits the self-incompatibility characteristic of all diploid species and of L. pallida. A self incompatible species would be cloned and used.
L. pallida is extensively cultivated for its edible pods and seeds. It is valued because it produces unripe pods earlier than L. esculenta, therefore extending the overall production period. Unripe pods, seeds and flower head buds are harvested and consumed locally as well as being transported to local and regional markets.
L. pallida is replacing L. leucocephala in forage production. Its hybrid with the latter is especially valued for its exceptional forage yields, psyllid resistance and its spreading branchy habit is ideal for forage production. However, the nutritive value of the species and the hybrid are doubtful due to their lower edible fraction, higher condensed tannin content and lower digestibility than L. leucocephala. Psyllid resistance of hybrids like L. leucocephala x L. pallida, however, exceeds that of any L. leucocephala, permitting higher fodder yields under psyllid attack and the short heavily forked trees are preferred for herbivore browsing. Most accessions of the tetraploid species L. pallida are low forking and they confer this trait to some of their hybrids with L. leucocephala, some low shrubby dwarfs also result.
L. pallida is used widely for firewood.
Timber: The hybrid L. diversifolia x L. pallida is psyllid resistant and grows as a pseudo-shrub with many long straight branches. Poles are commonly used in the production of vine crops (black pepper, passion fruit, pole beans) where long, straight, thin poles are preferred.
Nitrogen fixing: L. pallida is nitrogen fixing.
L. pallida is largely cultivated on terrace margins or field boundaries.
Soil improver: Lopped leaves and twigs can be applied as green manure.
Intercropping: Farmers in dry zones use L. pallida over crops as a tree fodder and in hedgerow agroforestry systems.