General Description | Pterocarpus indicus is a large tree with fragrant yellow flowers, large compound leaves, and disc-shaped fruit. It is the national tree of the Philippines, and is often used for timber. It is listed as endangered on the International Union for the Conservation of Nature Red List. |
ID Characteristic | Smooth Narra has fragrant yellow flowers, as well as thin, disc shaped fruit with obvious corky bulges in the middle. It also has pinnately compound leaves, with ovate leaflets possessing acuminate tips. |
Shape | Smooth Narra is a tall tree with a broad canopy. Its lower branches are semi-pendulous, and can often grow all the way near the ground. |
Landscape | P. indicus is commonly used for roadside plantings, as well as a way to mark field boundaries. It has high wind tolerance, making it an effective windbreak, and can assist with soil stabilization due to its wide, shallow root system. It can also be used as a shade tree, or as an ornamental planting due to its vibrant, ephemeral flowers. |
Propagation | P. indicus can be propagated through typical methods, such as using seeds, cuttings, or tissue cultures. It is recommended, if one plans to use seeds, to wait until the fruits change to a brown colouration, and then to manually remove seeds from the tree, either via cutting branches or shaking seeds off of the tree. Seeds can be extracted from their pods, though the effort required, along with risk of seed damage, is typically not worth the very slight germination improvement. A freely draining pottery medium should be used, and the fruit should be pushed
10 mm into it, and subsequently covered with a thin soil layer. If seeds have been extracted, they should be laid flat on the potting medium, and covered in 2 mm to 3 mm of soil. Seeds should be germinated in a place such as a shade house, with seedlings kept in light shade (around 25% to 50% shade) for about 2 to 4 weeks after being planted, and then brought into full sun for 6 to 8 weeks before any field planting occurs. Seeds will typically start germinating about 3 to 4 days after being sowed. Direct seeding is likely to work best when outplanting, though care must be taken to make sure predators and weeds don’t take over the growing area. If propagating from a cutting, it is best to use cuttings with a diameter of at least 6 cm for better rooting. The cuttings will fairly easily establish roots, though they tend to be at greater risk for
heart rot, so this method should be avoided if the trees are to be used for timber. Propagating through tissue culture, while possible, is generally not recommended, as Smooth Narra is generally easy to propagate through traditional methods. |
Cultivation | P. indicus grows best in tropical or subtropical regions, with free draining soil, though it has been known to grow near rivers, suggesting it has some level of waterlogging tolerance. It prefers a range of pH from moderately acidic to neutral, at around pH 4.0 to pH 7.4. Up to 25% shade is tolerated by the plant, but full sun is ideal. Its drought tolerance varies by area, but has been recorded as surviving 6 month dry periods in certain areas. Light or medium soils are acceptable for growing Narra, though it grows best in deep, loamy soil. |
Pests | In many parts of the cities of Malang and Batu in Indonesia, there are attacks from ambrosia beetles, causing fallen leaves and holes in the bark, with frass appearing around the holes. As well, outbreaks of the fungus Fusarium oxysporum have been recorded in countries such as Malaysia and Singapore. It is thought to be primarily spread by ambrosia
beetles carrying the spores, attacking trees that are rendered susceptible to infestation after lightning strikes. F. oxysporum causes the yellowing and subsequent wilting of leaves, and has spread internationally, causing actions to have to be taken in the past to research and control its spread in many countries. |
Notable Specimens | National Tropical Botanical Garden, Hawaii, United States. |
Habitat | P. indicus is native to parts of East Asia and South-east Asia, as well as the north and south-portions of the pacific region. It typically grows at elevations anywhere from 1 m to 1300 m, in areas that receive an annual rainfall of around 1300 mm to 4000 mm. |
Bark/Stem Description | Smooth Narra has large, high buttresses and a wide crown. Branches initially grow upwards, but often begin drooping downward, and can reach near the ground. The bark is a mix of grey and brown, while branches and branchlets are either light brown or dark brown. |
Flower/Leaf Bud Description | Flower buds appear on the upper leaf axils and terminal ends of branches. Once the buds are fully grown, they wait for a currently unknown trigger before opening for one day. |
Leaf Description | Smooth Narra has large, ovate or elliptic leaflets with acuminate tips and rounded bases, arranged in a compound-pinnate structure forming the
leaf. The size of the leaflets range from 7 x 3.5 cm to 11 x 55 cm, with the petiole being 1.5 cm to 4 cm long. A typical leaf will have about 5 to 11 leaflets, with the terminal leaflet being larger than the others. Each leaflet will have about 8 to 10 lateral vein pairs, while
the leaflet’s midrib is either flat or impressed above. |
Flower Description | Flowers are yellow and fragrant, appearing in the form of large axillary panicles, with panicles being 10 cm to 20 cm long. Each flower is approximately 1.5 cm long, and typically consists of 5 petals, with one ovate to orbicular standard petal, two oblong wing petals, and two oblong keel petals. |
Fruit Description | The fruit of Smooth Narra is round, flat, and shaped like a disc. It has thin, wing-like edges, and carries 1 to 3 seeds within a corky bulge in its centre. Each fruit is around 5 cm across, and primarily disperses via wind, but can also disperse via water by floating on the surface. The fruits of Pterocarpus indicus f. indicus are smooth, as opposed to the similar forma f. echinatus, which has bristles around the seed pod. |
Colour Description | Lovely lush green leaves, with the bright yellow flowers adding a beautiful contrast while they’re in bloom. The grey-brown bark adds to the more pale aesthetic, complimenting the leaves and flowers nicely rather than contrasting them. The flowers fall off at a similar time, creating beautiful sheets of yellow on the ground even after the main flowering period finishes. |
Texture Description | Narra has a medium texture, with its trunk being somewhat rough, yet not obscenely so. |