Pongamia pinnata aka Karanj

Pongamia pinnata prefers moist soil but is remarkably drought-tolerant once established. Young trees should be watered regularly to establish a strong root system, while mature trees require minimal supplemental watering. The tree naturally grows along coasts and tidal areas where its roots often contact water, yet it also thrives in seasonally dry tropical climates with extended dry periods. In cultivation, water moderately and allow soil to dry somewhat between waterings.

Pongamia pinnata is highly adaptable to different soil types, growing well in light sandy soils, medium loamy soils, and even heavy clay. It prefers deep, well-drained sandy loams with adequate moisture for optimal growth. However, nutrient deficiencies may appear in soils with pH above 7.5. As a nitrogen-fixing legume, it enriches the soil through symbiotic bacteria in its root nodules.

Pongamia pinnata grows well in both full sun and partial shade, demonstrating unusual flexibility for a large tree. While it thrives and produces the best flowering and fruiting in full sun conditions, it can also grow successfully under the canopy of taller trees. The University of Florida recommends full sun to partial shade for optimal growth. In its native habitat, the tree commonly grows along open coastlines and forest edges where it receives abundant sunlight.

Pongamia pinnata is a fast-growing medium to large tree that typically reaches 15-25 meters (50-80 feet) in height at maturity. The crown spreads equally wide, often matching or exceeding the height, creating dense shade. The trunk develops to 50-80 cm in diameter with grey-brown bark. Young trees grow rapidly, with seedlings reaching 25-30 cm in their first growing season and established trees adding approximately 1.3 meters of height annually in favorable conditions. Trees begin producing seed pods when 5-7 years old.

Pongamia pinnata produces attractive, fragrant pea-like flowers from February to June, with peak flowering in April-May during the dry season. The flowers appear in clusters on lateral and terminal racemes measuring 5-27 cm long. Flower colors range from white to pink and lavender. The blooms are highly attractive to bees and other pollinators, making Pongamia a valued honey plant in India. Following successful pollination, brown oval seed pods develop from April through October.

Pongamia pinnata is most commonly propagated from seed, which requires no pre-treatment and germinates within 1-5 weeks of sowing. Seeds undergo hypogeal germination with rapid radicle development. Seedlings reach 25-30 cm in their first year and should be transplanted at 60 cm height at the start of the rainy season. Seeds remain viable for approximately one year when stored in airtight containers. The tree can also be propagated from stump cuttings, branch cuttings, and root suckers, and it coppices well when cut back.

Pongamia pinnata is exclusively an outdoor tree suited to USDA hardiness zones 10-12. It is native to tropical and subtropical regions and cannot tolerate freezing temperatures below -1°C (30°F), though mature trees can survive light frosts. The tree excels in coastal locations due to its high tolerance for salt spray and saline soils. It is well-suited for Florida, Hawaii, and other tropical/subtropical regions.

Pongamia pinnata is pollinated by insects, primarily bees. Research has documented 13 flower visitor species, with Megachile (leafcutter bees), Apis (honeybees), and Xylocopa (carpenter bees) being the most abundant. The fragrant flowers produce copious nectar and pollen, attracting numerous pollinators. The flowers feature an explosive pollen release mechanism triggered by bee activity. Without insect pollinators, the tree produces no seed pods, while open pollination results in 15-18% pod set. The tree is valued as a honey plant, with bees producing characteristic dark honey from its nectar.

Pongamia pinnata thrives in tropical and subtropical climates with mean annual temperatures ranging from a minimum of 1-16°C to a maximum of 27-38°C. The tree is sensitive to frost and cannot tolerate temperatures below -1°C (30°F), though mature specimens can survive brief light frosts. It grows best in warm conditions with seasonal dry periods and is naturally found from sea level to elevations of 1,200 meters. The tree is well-adapted to regions with distinct wet and dry seasons and tolerates a wide temperature range within its tropical limits.

Pongamia pinnata is notably resistant to pests and diseases. The University of Florida IFAS reports no major pest or disease concerns for this species, noting only that caterpillars occasionally cause minor defoliation. The tree's natural pest resistance, combined with its drought tolerance and adaptability to poor soils, makes it a robust choice for challenging growing conditions. The presscake from seed oil extraction is actually valued as a natural pesticide, particularly effective against soil nematodes.

Pongamia pinnata has extensive traditional medicinal uses throughout its native range, earning a 3/5 medicinal rating. The seed oil is applied externally for skin diseases including leucoderma and scabies, and for rheumatic joints. Powdered seeds serve as an expectorant for bronchitis and whooping cough. Leaf infusions relieve rheumatism, while leaf poultices treat parasitic skin conditions and hemorrhoids. The flowers are claimed to have anti-diabetic properties. Stem bark is used as an astringent for bleeding hemorrhoids and to reduce spleen enlargement. Root juice serves as an antiseptic for ulcers and dental hygiene.

Pongamia pinnata has numerous practical uses, earning a 4/5 rating. The seed oil (27-40% content) serves as a lubricant, varnish, paint binder, soap ingredient, and traditional lamp fuel. More recently, it has gained attention as a biofuel source. The wood is used for cabinet-making, cartwheels, tool handles, and fuel. Bark fibers produce rope and twine. The presscake is valued as a natural pesticide against soil nematodes. Dried leaves repel grain storage insects. The tree is used for erosion control, windbreaks, and as a host plant for sandalwood cultivation. Leafy twigs serve as green manure for rice, sugarcane, and coffee.

Pongamia pinnata responds well to pruning and can be pollarded or coppiced. When grown as a shade or ornamental tree, regular pruning may be needed to achieve an appropriate trunk height and control the spreading crown. The tree produces large quantities of shed flowers, leaves, and pods, which some consider messy for ornamental purposes. Pruning helps maintain a tidy appearance and can control the tree's size. Young trees should have lower branches removed gradually to develop a clean trunk. The tree regenerates vigorously from pruning cuts.

Yes, Pongamia pinnata produces fragrant flowers. The pea-like blooms emit a pleasant scent that attracts numerous pollinators, particularly bees. The fragrance is most noticeable during the main flowering season from February to June. The University of Florida IFAS describes the flowers as 'fragrant clusters' and this pleasant scent is one reason the tree is sometimes planted as an ornamental in suitable climates. The flowers are valued by beekeepers as they produce nectar for a characteristic dark honey.