Common Name: Rain Tree

General Information

Samanea saman is an attractive, large, spreading deciduous tree with a low, dense, dome-shaped crown; it usually grows up to 30 metres tall with occasional specimens to 60 metres[, , ]. It has a short, usually crooked bole that can be up to 200cm in diameter[, ]. Trees can be evergreen in humid climates[].
A multipurpose tree, it is often cultivated for its many uses. It is particularly valued for its timber, but also supplies food, medicines and a gum. It is one of the most commonly planted avenue and park trees in the tropics and is also commonly grown as a shade tree for other crops[].

Known Hazards

None known

Botanical References

Range

Northern S. America - Colombia, Venezuela; north through Central America to Nicaragua and El Salvador.

Habitat

Dry lowland grassland, coastal bushland and forest[]. Dry forest and grass savannah, or at the margins of seasonally dry deciduous and semi-deciduous forest as well as moister evergreen woodland and savannah[]

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	25.00 m
Growth Rate	Fast
Pollinators	Bees, Lepidoptera
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

A plant of the lowland, humid tropics, growing from sea level to an elevation of 1,300 metres[]. It prefers a mean annual temperature in the range 20 - 35°c, being liable to damage if temperatures ever drop below 8°c. It tolerates a mean annual rainfall in the range 600 - 3,000mm[]. In areas of high rainfall the tree has a tendency to be shallow-rooted, but is deep rooted when grown in drier areas[].
Prefers a position in full sun[]. A fairly easy tree to grow, tolerant of a range of conditions, it grows on light or heavy soils and tolerates infertile or waterlogged conditions[]. Normally found on neutral to moderately acid soils, it can grow on soil with pH as low as 4.6[]. Established plants are very drought tolerant[].
Samanea saman possesses some of the characters of other species known to have become invasive - these include. prolific seeding; livestock as effective dispersers of seed; nitrogen fixation; and adaptation to a variety of soil types. However, reference sources are somewhat conflicting as to the degree of naturalization and invasion, especially where it spreads on disturbed sites often in Pacific and Caribbean islands. The species is generally considered to be only moderately invasive[]. The tree is listed as undesirable in environmentally sensitive areas of Australia[].
The tree grows slowly in the first year of planting, but is generally considered to be fast growing with annual height increases of up to 150cm recorded for young trees[, ]. It responds to pruning and coppices well, regrowing rapidly when lopped or pollarded[].
Yields of up to 275 kilos of pods per year can be obtained from trees 15 years old[].
The trees provide a microclimate effect for the plants growing under their canopies. At night and on cloudy days, branches hang down and the leaves fold down and inward, allowing rain to fall directly on the ground and promoting cooling through exposing the ground[]. In the morning the leaves unfold and resume a horizontal position, giving full shade and helping to preserve moisture[]. The species is used as a shade for tea, coffee, cocoa, nutmeg and vanilla, and provides shade for pasture and grazing animals[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Children eat the pods, which contain a brownish, sticky, liquorice-like, sweet-flavoured pulp[, ]. A lemon-like fruit drink is also made from the pulp[, ]. The pods are more or less straight with conspicuously thickened edges, 12 - 20cm long, 1 - 2cm wide and 1.2cm thick[].

The tree yields a gum of inferior quality which could be used as a poor man's substitute for gum arabic[].

Medicinal

A decoction of the inner bark and fresh leaves is used as a treatment for diarrhoea[].

A brew of small sections of the bark is taken to treat stomach-ache[].

A crude aqueous or alcoholic extract of the leaves is observed to have an inhibiting effect on Mycobacterium tuberculosis[]. The alkaloid fraction of the leaves is effective on the CNS and PNS[]. An infusion of the leaves is used as a laxative[].
A decoction of the fresh material is used as a wash in the treatment of skin problems such as dermatitis, eczema and pruritus[].

The fruit decoction is used as a CNS-sedative[].

The seeds are chewed for treating a sore throat[].

Agroforestry Uses:

The tree is grown to provide shade for other crops, including cocoa, coffee, tea and peppers[, ]. The dome-shaped, low crown provides a very strong shade even at low sun positions[]. The leaves fold up during rain, allowing more moisture to reach the crops below[].

Other Uses

The bark is an abundant source of gums and resins[, ]. The tree yields a gum of inferior quality which could be used as a poor man's substitute for gum arabic[]. It can be used as an adhesive[].

Pods can be ground up and converted to alcohol as an energy source[]. Yields of 1,150 litres of absolute alcohol can be obtained per year from 1 hectare[].

The heartwood is brown when freshly cut, turning golden-brown upon exposure; the thin layer of sapwood is a cream colour. The wood is light in weight; soft but strong; durable to very durable. It takes a high polish but is often very cross-grained, making it difficult to work except when green. With its rich dark-and-light pattern, the wood is highly prized for carvings, furniture and panelling. The wood shrinks so little that products may be carved out of green wood without fear of splitting or warping as the wood dries[, ]. In Hawaii, bowls and other craft products made from the wood are in such high demand that the local wood supply is supplemented by imports from Indonesia and the Philippines[]. A moderately durable wood, it is also used in boat building[]. The wood is very durable against rot and termites[]. The beautiful, high-quality wood is used for interior trim, crafts, boxes, veneer, plywood and general construction[].
The fact that the wood produces 5,200 - 5,600 kcal/kg when it burns, and that it regrows vigorously after lopping or pollarding, makes it a valuable source of high-quality firewood and charcoal[]. However, where there is a strong market for wood carvings, the wood is considered too valuable to be used as fuel[].

Propagation

Seed - stores well at ambient temperatures[]. Fresh seed that is still moist usually germinates freely without pre-treatment[]. Once the seedcoat has dried and hardened it needs to be treated to allow the ingress of moisture. This can be dome by carefully making a nick in the seedcoat (being careful not to damage the seed) or soaking larger quantities of seed in hot water for 3 minutes. In either case, the seed is then soaked for 12 - 24 hours in warm water before sowing[]. Treated seed usually germinates quickly, in 6 - 8 days under optimal conditions[].
Cuttings.

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