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Samanea saman (Jacq.) Merr.

Mimosaceae
Rain tree

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

With a checkerd nomenclature, under Enterolobium in the Wealth of India, Pithecellobium in Common Trees of Puerto Rico, and Samanea in Woody Plants of Ghana, the rain tree is apparently widely traveled. Perhaps one of its most important uses in Latin America is as a shade tree, especially in parks, pastures, and roadsides. Improved growth, nutritive quality, protein content, and yield have been demonstrated by Axonopus compressus, a tropical forage grass, grown under Samanea. "The benefit by association was presumptively attributed to nitrogen made available in the soil by excretion or decomposition of the leguminous nodules." (Allen and Allen, 1981). The tree house in Walt Disney's "Swiss Family Robinson" was built in a rain tree 60 m tall with a canopy 80 m in diameter. Simon Bolivar is said to have encamped his entire liberation army under the "saman de guerra" near Maracay, Venezuela. In Malagasy, it is grown as shade tree for cacao, coffee, patchouly, and vanilla. In Indonesia, it is recommended for nutmeg but not for tea. In Uganda, it is considered good for coffee, bad for tea. According to NAS (1980a), "Grass grows right up to the trunk because this species' leaflets fold together at night and in wet weather, allowing the rain to fall through." Like Acacia, Ceratonia, Prosopis, and Tamarindus, this produces copious pods with a sweet pulp, attractive to children and animals alike. Pods can be ground up and converted to fodder or for that matter alcohol as an energy source. A lemon-like beverage can be made from the pulp. The wood is soft, lightweight (spec. grav. 0.44; 720–880 kg/m3) of medium to coarse texture, fairly strong, takes a beautiful finish but is often cross-grained and difficult to work. It is used for furniture, general construction, and interior trim, for boxes and crates, panelling, plywood, and veneer. Central American oxcart wheels are made from cross sections of trunks. It is used for boat building in Hawaii, where it is also famous for making "monkeypod" bowls. Shavings from the wood are used for making hats in the Philippines. The tree yields a gum of inferior quality which could be used as a poor man's substitute for gum arabic. Like most other mimosaceous trees, this is an important honey plant. Rain tree is one host of the lac insect, which, however, produces a poor quality lac, reddish and rather brittle (C.S.I.R., 1948–1976).

Folk Medicine

According to Hartwell (1967–1971), the root decoction is used in hot baths for stomach cancer in Venezuela. Rain tree is a folk remedy for colds, diarrhea, headache, intestinal ailments, and stomachache (Duke and Wain, 1981). The alcholic extract of the leaves inhibits Mycobacterium tuberculosis (Perry, 1980). The alkaloid fraction of the leaves is effective on the CNS and PNS. In Colombia, the fruit decoction is used as a CNS-sedative. The leaf infusion is used as a laxative (Garcia-Barriga, 1975). In the West Indies, seeds are chewed for sore throat (Ayensu, 1981).

Chemistry

Per 100 g, the green leaf is reported to contain 47.8 g H2O, 10.2 g protein, 2.1 g fat, 22.2 g insoluble carbohydrate, 15.7 g fiber, and 2.0 g ash. On an oven-dry basis, the leaves contain ca 3.2% N. Gohl, 1981 tabulates as follows:
As % of dry matter
DM CP CF Ash EE NFF Ca P
Fresh twigs, late vegetative, Malaysia 38.9 24.7 22.1 4.4 2.8 46.0 0.55 0.26
Fresh leaves, Thailand 39.1 22.1 29.4 6.0 7.0 35.5 1.42 0.21
Fresh leaves, Trinidad 34.4 30.0 29.0 3.5 3.5 34.0
Pods, Jamaica 79.5 12.8 14.5 2.4 0.7 69.6 0.29 0.32
Pods, fallen, Trinidad 85.0 18.0 10.9 4.6 1.4 65.1
Seeds, Jamaica 86.5 31.6 14.0 4.3 6.0 44.1 0.16 0.34
Whole pods contain: moisture, 15.3; ash, 3.2; fat, 2.1; protein, 12.7; 11.4; and carbohydrates, 55.3%. Kernels contain: moisture, 16.1; ash, 3.0; fat, 1.3; protein, 10.6; CF, 10.8; and carbohydrates, 42.0%. The bark contains two alkaloids—C8H17ON and C17H36ON3 (pithecolobine; LD50 in mice 40–225 mg/kg)—and a saponin (samarin), which yields on hydrolysis an aglucone of the formula C23H36O4, arabinose, glucose and rhamnose. Samarin is an irritant to isolated intestine. Other constituents identified in the bark are gallic acid, glucose, sucrose, fatty acids and a phytosterol. Wood contains: lignin, 30.44; cellulose, 50.89; a-cellulose, 38.35; and ash, 0.27% (C.S.I.R., 1948–1976). Hager's Handbook (List and Horhammer, 1969–1979) reports hexacosanol, lupeol, a-spinasterol, octaconsanolic acid, a-spinasterol-b-D-glucoside, a-spinasterone, and lupeone from the rind, hentriacontane and octacosanol from the leaves; a-spinasterol, and its b-D-glucoside, palmitic, and stearic acid from the seed kernel, three flavonoids and kaempferol from the testae, and a-spinasterol and octacosabolic acid from the wood.

Description

Large umbraculiform tree to as much as 60 m tall, the crown to 80 m broad, covering 1/5 hectare, trunk to 1.5 m DBH, unarmed, with gray rough furrowed bark. Leaves alternate, evergreen, bipinnate, 25–40 cm long, with 2–6 pairs of pinnae, each of which bears 6–16 paired stalkless leaflets, with a glandular dot between each pair. Flower heads clustered near the end of twigs, each cluster on a green hairy stalk 7–10 cm long, with many small tubular pinkish-green flowers, calyx and corolla 5-toothed. The many stamen united to form a tube near their bases, seed pods oblong, flat, arcuate, black, 20–30 cm long, with a raised border, each with several oblong reddish-brown seeds ca one cm long.

Germplasm

Reported from the South American Center of Diversity, rain tree, or cvs thereof, is reported to tolerate drought, poor soils, waterlogging and weeds. (2n = 26)

Distribution

Native from the Yucatan Peninsula and Guatemala to Peru, Bolivia, and Brazil. Widely planted and naturalized elsewhere in continental tropical America from Mexico southward, throughout the West Indies (except Bahamas), and in Old World tropics. Grown also in southern Florida (Little and Wadsworth, 1964).

Ecology

Ranging from Subtropical Very Dry to Moist through Tropical Dry to Moist Forest Life Zones, rain tree is reported to tolerate annual precipitation of 6 to 25 dm (mean of 49 cases = 14.0), annual temperature of 21.6 to 28.5°C (mean of 36 cases = 25.8), and pH of 6 to 7.

Cultivation

Easily propagated from seeds and cuttings. Young specimens transplant easily.

Harvesting

Lopped for forage or timber at any time, it can be maintained at any height by periodical pruning.

Yields and Economics

A full grown tree 15 years old is said to yield ca 200–275 kg pods per season, which translates to 10 MT/pods, if we can crowd 50 productive trees to the hectare. A single tree 5 years old has been said to yield nearly 550 kg green forage (assuming 50% moisture = ca 275 kg DM). Assuming 50 trees to the hectare, that translates to nearly 14 mT forage in leaves.

Energy

According to figures in the Wealth of India, 10 MT pods would yield 1150 liters of absolute alcohol, roughly 5–10 barrels ethanol/ha/yr. It is reportedly used as an alcohol source in Colombia. Use of the wood as a fuel is not often reported. In the Philippines, Quisumbing (1951) reports the branches and trunk are used as firewood.

Biotic Factors

Browne (1968) lists: Fungi. Fomes annularis, Ganoderma australe, Ganoderma lucidum. Coleoptera. Anomala antiqua, Apate monachus, Lepropus chrysochlorus, Oncideres tessellata. Hemiptera. Ferrisia virgata, Hemiberlesia lataniae, Icerya aegyptiaca, Icerya formicarum, Kerria lacca, Ptyelus flavescens, Rastrococcus iceryoides. Isoptera. Coptotermes amanii. Lepidoptera. Attacus atlas, Homona coffearia, Indarbela quadrinotata, Melisomimas metallics. Mammalia. Callosciurus caniceps. Also occuring on Samanea saman are Hypomyces haematococcus; root knot nematodes, Meloidogyne sp.; and the leaf spot Microstroma pithecolobii.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw