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The Narra Tree
| By goGreen | August 26, 2011 |  |
Distribution: Native to Southeast and East Asia and to the northern and southwest Pacific region; now distributed widely throughout the tropics.
Size: Typically reaches 25–35 m (82–115 ft) in height with a broad canopy when grown in the open.
Habitat: Grows at elevations of 1–1300 m (3.3–4300 ft) with annual rainfall of 1300–4000 mm (50–160 in).
Vegetation: Thrives best in riverine, closed, and secondary forests.
Soil: Adapted to a range of soils, growing best on deep, fertile, loamy, alluvial soils.
Growth rate: In optimal conditions, height growth may be 2 m/yr (6.6 ft/yr) for the first 3–4 years, slowing to about 1 m/yr (3.3 ft/yr) thereafter.
Main product: Timber.
Yields Estimated: at 5–10 m3/ha/yr (72–144 ft3/ac/yr) over a 30–40 year rotation, on optimal sites.
Intercropping: Planted as boundary and windbreak around food crops or as a living fence around pastures.
Invasive potential: Has limited potential to invade undisturbed native plant communities.
BOTANICAL DESCRIPTION
Preferred scientific name: Pterocarpus indicus Willd.
Genus Name: derived from the Greek pteron, which means wing, and karpos, which means fruit, referring to the flat, winged pods characteristic of the genus.
Family: Fabaceae (legume family) Subfamily: Faboideae
Non-preferred scientific names:
Pterocarpus carolinensis Kaneh.
Pterocarpus draco sensu auct.
Pterocarpus indica Willd.
Size and form: A briefly deciduous, majestic, large tree typically growing to 25–35 (–48) m (82–115 [–160] ft) tall and about the same canopy width in open situations. Trees have a large, rather dense canopy. The semi-pendulous lower branches may extend to near ground level in open sites.
Flowers: Flowering is often initiated before the new leaf flush but continues after leaf flushing. Flowering takes place in several short bursts of about 1–2 days duration. The pea-shaped flowers are bright yellow to orange-yellow, about 1.5 cm (0.6 in) long, fragrant, and arranged in branched axillary racemes. The flowers are borne in profusion adding to the ornamental appeal of trees when in full flower. Seasonality of flowering varies geographically.
Leaves: The bright green, imparipinnate leaves are arranged alternately on the branchlets. Trees are either briefly fully deciduous or may be evergreen in uniformly humid zones. The new flush of leaves is light green, turning dark mid-green. Each leaf has (5–) 7–9 (–11) alternately arranged, ovate leaflets; each leaflet is about 6–12 cm (2.4–4.8 in) long by 3–7 cm (1.2–2.8 in) wide, with an entire margin. The terminal leaflet is larger, with the smallest leaflets in the lowest pair on the rachis
Fruit: The pods are thin, papery winged, disc-shaped, about 5–6 cm (2–2.4 in) across, and borne in clusters. They are light green, turning dull brown when fully mature
Seeds: The seeds are flattened, bean-shaped, 6–8 mm (0.2–0.3 in) long with a leathery, although rather brittle, seed coat. Pod/ seed dispersal is mainly by wind. Pods can float, and water dispersal is likely to also be significant for riverine populations.
Rooting habit: Trees have a well developed near-surface lateral rooting structure. Young plants compete poorly with Imperata and other tall, vigorous grasses and need to be regularly weeded on grassy sites. For establishment on grassy sites, good pre-planting control of grasses is essential, and a once-only treatment with glyphosate herbicide is recommended for this purpose. Because roots can grow large near the surface, it is best to grow the tree well away from sidewalks and pavement.
PROPAGATION
Narra can be propagated from seeds, cuttings, grafting, and tissue culture. Seedlings and large branch cuttings are the most common methods of propagation.
Seed collection
The time for collection of ripe fruits varies by region. Pod maturity is indicated by a color change from light green to brown. Some pods fall or disperse soon after maturing, but most remain on the tree for several months. It is preferable to collect mature fruits by climbing into the canopy and lopping fruit-laden branches or else shaking and/or beating with long poles to dislodge fruits onto tarpaulins on the ground.
Seed processing
Fruits may be de-winged in order to reduce bulk and improve storability. Dewinging is done using a hammer mill or brushing machine fitted with hard brushes. There are about 1500–3000 (Av=2300) air-dried pods per kg (3300–6600 [Av=5000] pods/lb). Typically about 50% of fruits contain one healthy seed, but the percentage of viable seed may be as low as 10–20%. With about 50% of fruits containing one healthy seed, there are 1200–1300 seeds/kg (2640–2860 seeds/lb) of air-dried pods. There are about 13,000 extracted seeds/kg (28,600 seeds/lb).
Seed storage
Storage behavior is orthodox, with seed being able to be safely dried down to 4% moisture content. The initial moisture content of seeds was found to be around 16–17% on a fresh weight basis. The most suitable method for longer- term storage, i.e., several years, is to store de-winged fruits at low temperature and moisture content.
Seed pretreatment
Seeds are typically sown still encased in their indehiscent pod into either open nursery beds, seed trays, or directly into individual containers (especially if extracted seed is used). The germination rate is improved if seeds are extracted from the pod before sowing; however, no pretreatment is required for germination. Seed extraction is not recommended for routine sowing, as it is a slow, manual process, often resulting in some damage to extracted seeds (and reducing their viability and/or storage life).
Growing area
It is preferable to germinate seeds in a sheltered area, such as a shade house. Seedlings should also be kept in sheltered areas with light shade (25–50%) for 2–4 weeks after transplanting.
They may then moved into an open nursery situation and should be grown and hardened in full sunlight for at least 6–8 weeks prior to field planting. Seedlings derived from direct-sown fruits may be grown in the open if nursery infrastructure is unavailable.
Germination
The fruits are pushed, on the flattened side, into soil to a depth of about 10 mm (0.4 in), and then covered with a thin layer of soil. If extracted seeds are used, they should be laid flat and shallowly covered with 2–3 mm (0.08–0.12 in) of media/soil. Light shade should be provided, and the seedbed mulched. Seeds begin to germinate 3–4 days aftersowing. The germination rate is about 24–40% at 4–15 days after sowing. Transplant germinants into individual pots at the cotyledon or four-leaf stage.
USES AND PRODUCTS
- Narra produces a beautifully figured and richly colored timber with excellent working and technical properties.
- Narra wood is durable in salt water, particularly the wood obtained from trees growing near the sea, and is a preferred species for canoes and boats and their accessories.
- It is one of the Asia-Pacific region’s finest timbers, and it is highly favored for use in interior joinery, paneling, decorative flooring, musical instruments, precision tools, and handicrafts.
- Different parts of the tree, notably bark extracts, are used in the treatment of a wide range of ailments and illnesses, particularly those pertaining to the digestive system and skin. In recent years, herbal teas and pills made from narra extracts have been popularized in the Philippines for treating a wide range of diseases and ailments including leprosy, menstrual pain, flu, rheumatoid arthritis, and diabetes.
- The heartwood contains various red compounds, and in the Philippines the heartwood is used to make a red dye. The bark extract can be used for tanning.
- An infusion from the leaves is sometimes used as shampoo in the Philippines. It is also the Philippines’ national tree.
The species is also widely planted for amenity purposes due to its
- ornamental appeal (large spreading habit, excellent shade tree, and masses of fragrant yellow flowers)
- stability and wind-firmness
- ease of establishment and quick landscape impact through use of large branch cuttings
- longevity
Source: Species Profiles for Pacific Island Agroforestry
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