Agroforestree Database

Local names:
 Arabic (um al shuur), Bengali (karanj,s[aa]m hoa,karanja), Burmese (thiuwia), Cantonese (honge), English (karum tree,Indian beech,pongam,poonga-oil-tree,oil tree,seashore mempari,pongam oil tree), Filipino (báni), French (arbre de pongolote), Hindi (kara

Pongamia pinnata is a medium-sized evergreen or briefly deciduous, glabrous shrub or tree 15-25 m high, with straight or crooked trunk 50-80 cm or more in diameter and broad crown of spreading or drooping branches. Bark grey-brown, smooth or faintly vertically fissured. Branchlets hairless with pale stipule scars.

Leaves alternate, imparipinnate with long slender leafstalk, hairless, pinkish-red when young, glossy dark green above and dull green with prominent veins beneath when mature. Leaflets 5-9, paired except at end, short-stalked, ovate elliptical or oblong, 5-25 x 2.5-15 cm, obtuse-acuminate at apex, rounded to cuneate at base, not toothed at the edges, slightly thickened.

Inflorescence raceme-like, axillary, 6-27 cm long, bearing pairs of strongly fragrant flowers; calyx campanulate, 4-5 mm long, truncate, finely pubescent. Flower clusters at base of and shorter than leaves, to 15 cm long, slender, drooping. Flowers 2-4 together, short-stalked, pea-shaped, 15-18 mm long. Calyx campanulate, 4-5 mm long, truncate, finely pubescent; corolla white to pink, purple inside, brownish veined outside, 5-toothed, standard rounded obovate 1-2 cm long, with basal auricles, often with green central blotch and thin silky hairs on back; wings oblong, oblique, slightly adherent to obtuse keel.

Pods borne in quantities, smooth, oblique oblong to ellipsoid, 3-8 x 2-3.5 x 1-1.5 cm, flattened but slightly swollen, slightly curved with short, curved point (beaked), brown, thick-walled, thick leathery to subwoody, hard, indehiscent, 1-2 seeded, short stalked. Seed compressed ovoid or elliptical, bean-like, 1.5-2.5 x 1.2-2 x 0.8 cm, with a brittle coat long, flattened, dark brown, oily. 

This species has been placed alone in its genus Pongamia, derived from the Malabar local name (pongam). In 1972, S. R. Bennet, an Indian taxonomist gave the pongam a new name, Derris indica (Lamk.) Bennet, but this change has not been generally adopted. The name Derris, derived from Greek, means ‘leather covering or skin’; the specific name ‘indica’ obviously means of India.

Ecology

P. pinnata is native to humid and sub-tropic environments; common along waterways or seashores, with its roots in fresh or saltwater. It is very tolerant of saline conditions and alkalinity, and occurs naturally in lowland forest on limestone and rocky coral outcrops on the coast, along the edges of mangrove forest and along tidal streams and rivers. It is a shade bearer and can grow under the shade of other trees; it is, however, not a shade demander and grows well even with full overhead light. It is also drought resistant and well adapted to adverse climatic conditions and soil moisture conditions; prolonged drought may however kill seedlings. In its natural habitat, the species tolerates a wide temperature range. Mature trees withstand light frost, waterlogging and tolerate temperatures of up to 50 deg. C. In addition to rain, trees require a dry season of 2-6 months.

Native range
Bangladesh, India, Myanmar, Nepal, Thailand

Tree management

Seedling survival and growth benefit from annual weed control for the first 3 years after transplanting. Growth of young trees is fairly slow; a growth of 1.3 m in height and 0.4 cm in diameter in 13 months was recorded in India. Trees coppice well and can also be pollarded. When planted as a shade or ornamental tree, pruning may be necessary to obtain a trunk of appropriate height. The spacing adopted in avenue planting is about 8 m between plants. In block plantings, the spacing can range from 2 x 2 m to 5 x 5 m. 
The lateral spread of roots on this species, about 9 m in 18 years, is greater than most other species; moreover it produces root suckers profusely. Because of these characteristics, pongam is unsuitable for agroforestry and has the potential to become a weed if not managed carefully. Individual trees yield 9-90 kg of pods annually, while mature trees yield 8-24 kg of seeds annually.

Seed storage behaviour is orthodox and seeds remain viable for about a year when stored in air-tight containers. There are 1 500-1 700 seeds/kg.

P. pinnata is native to humid and sub-tropic environments; common along waterways or seashores, with its roots in fresh or saltwater. It is very tolerant of saline conditions and alkalinity, and occurs naturally in lowland forest on limestone and rocky coral outcrops on the coast, along the edges of mangrove forest and along tidal streams and rivers. It is a shade bearer and can grow under the shade of other trees; it is, however, not a shade demander and grows well even with full overhead light. It is also drought resistant and well adapted to adverse climatic conditions and soil moisture conditions; prolonged drought may however kill seedlings. In its natural habitat, the species tolerates a wide temperature range. Mature trees withstand light frost, waterlogging and tolerate temperatures of up to 50 deg. C. In addition to rain, trees require a dry season of 2-6 months.

Natural reproduction is profuse by seed and common by root suckers. Spontaneous seedlings and root suckers are produced and may cause serious weed problems. 
Direct sowing is common and most successful. Seeds require no pre-treatment and germinate within 7 days to 1 month of sowing. Germination is hypogeal and the radicle develops quickly before the plumule emerges. In the nursery, it can be planted at a close spacing, as young plants tolerate shade well; in India a spacing of 7.5 x 15 cm is recommended. Seedlings attain a height of 25-30 cm in their first growing season. Transplanting to the field should occur at the beginning of the next rainy season when seedlings are about 60 cm in height. Seedlings have large root systems and soil should be retained around the roots during transplanting. Easily established by direct seeding or by planting nursery-raised seedlings or stump cuttings of 1-2 cm root-collar diameter. Propagation by branch cuttings and root suckers is also possible.

Poison:  The presscake, when applied to the soil is valued as a pesticide, particularly against nematodes. In rural areas, dried leaves are stored with grain to repel insects. Pounded and roasted seeds used to be utilized as fish poison.

Because it tolerates moderate levels of salinity, pongam is an ideal candidate for recovering a variety of wastelands such as saline soil reclamation. It is also used in reforestation of marginal land.

Erosion control:  A preferred species for controlled soil erosion and binding sand dunes because of its extensive network of lateral roots.

Opinions vary on the usefulness of P. pinnata as a fodder; its value is greatest in arid regions. The leaves can be eaten by cattle and are readily consumed by goats however it is not common. The leaves contain 43% dry matter, 18% crude protein, 62% neutral detergent fibre, and in vitro dry matter digestibility of 50%. The presscake (seed residue) after oil extraction is bitter and unfit for use as a sole animal feed. It is high in protein but posses several toxic factors, particularly karanjin, pongamol and tannin. It is suggested as a short-term substitute for other protein sources but never serving as more than a 75% replacement.

Apiculture:  P. pinnata flowers are considered a good source of pollen for honeybees in India and they yield adequate nectar. 

With a calorific value of 4 600 kcal/kg, pongam is commonly used as a fuelwood. The seed oil was formerly indispensable as an illuminant in lamps, but has been largely replaced by kerosene.

Fibre:  The bark fibre is made into string, twine or rope, and the wood provides paper pulp. 

Timber:  Wood varies from white to yellowish-grey with no distinct heartwood; beautifully grained and medium to coarse textured. Although it is a moderately strong timber that is relatively easy to saw, turn and finish, the wood is not considered a quality timber because it is not durable, tends to split and warp during seasoning and is susceptible to insect attack. The wood is used for cabinet making, cartwheels, posts, agricultural implements, tool handles and combs. 

Shade or shelter:  Grass grows normally beneath the tree so it has been planted for shade in pastures. P. pinnata is grown as a windbreak for tea plantation in Sri Lanka.

Tannin or dyestuff:  Roots yield a natural pigment, pinnatin, which was synthesized in 1967. The wood ash is employed in dyeing. Oil from the seeds is used for leather dressing in tanning industries. 

Lipids:  Oil is the most important product of the pongam tree and vast amounts of seeds are collected in India for commercial processing of industrial uses. It has been found that the seed contains 27-40% of a thick, yellow or reddish-brown oil and that 2 kg of mature pods will yield about 1 kg of husked kernels. Extracted oil amounts to 13.4% of the whole seed pod; 26.97% of the kernels. The oil has a bitter taste, a disagreeable aroma and a specific gravity of 0.9371 at 15 deg. C. It is used as a lubricant, varnish, water-paint binder and in soap making. It is one of the few nitrogen-fixing trees to produce seeds containing oil.

Medicine:  The seed oil is rubbed as liniment on skin diseases and rheumatic parts. Internally, it is given as a stomachic and cholagogue in dyspepsia and cases of sluggish liver. A seed powder is given as an expectorant in bronchitis and whooping cough, and is also prescribed as a ferbifuge and tonic. Seed paste is spread on sores and rheumatic parts. An infusion of the leaves is used to relieve rheumatism, a decoction is a cough remedy, expressed juice is used on herpes and itches, and when they are crushed, applied as a poultice for the treatment of parasitic skin diseases. The flowers are claimed to have anti-diabetic action. Fresh stem bark is applied to reduce the enlargement of the spleen. It is astringent and taken internally to relieve bleeding heamorrhoids while a poultice of young leaves is laid on externally. The root bark contains a bitter alkaloid and is employed by the people of Guimaras Island in the Philippines as an abortifacient. The antiseptic root juice is put on sores and ulcers and used to clean teeth. 

Nitrogen fixing:  Nodulation is reported on pongam. In nurseries and fields the presence of nodules on uninoculated pongam seedlings is common. Therefore, this species may not be specific in its Rhizobium strain requirement. It nodulates and fixes atmospheric nitrogen with Rhizobium of the cowpea group.

Ornamental:  P. pinnata is often planted in homesteads as an ornamental tree and in avenue plantings, roadsides, and stream and canal banks. However the large amounts of flowers, leaves and pods that it regularly sheds make it not very suitable for this purpose.

Soil improver:  Incorporation of leaves and the presscake into soils improves fertility. Decomposed flowers are valued in the tropics as rich nutrition for special plants, especially when grown in greenhouses.