The Raintree (Monkeypod) (Samanea saman, Pithecellobium saman) is of the Leguminosae family. It is a fast growing tree native to Central America and northern South America (Southern Mexico (Yucatan Peninsula) and Guatemala southward to Peru, Bolivia, and Brazil.). Hardy in zones 10 & 11.

It is considered an ornamental tree but also used as a shade tree. The tree can attain heights from 100 to 125 ft and trunk diameters of 3 to 4 ft. When grown in the open, it develops a massive wide-spreading crown and a short thick trunk; it forms a long, relatively straight stem when closely spaced. It has been naturalized in many countries and is greatly valued in pastures as shade for cattle.

The most widely used common name for the species is raintree, from the belief that the tree produces rain at night. The leaflets close up at night or when under heavy cloud cover (this is my personal favorite aspect of this tree - as even the new growth leaves from the seedling show this trait), allowing rain to pass easily through the crown. This trait may contribute to the frequently observed fact that grass remains green under the trees in times of drought. However, the shading effect of the crown, the addition of nitrogen to the soil by decomposition of litter from this leguminous tree, and possibly, the sticky droppings of cicada insects in the trees all contribute to this phenomenon.

It may bloom sporadically throughout the year, but primarily during the summer months. It bears beautiful glowing pink flowers followed by attractive green and black pods that contain a sweet pulp. Seed pods are edible. The flowers are in loose heads; corolla greenish-yellow, stamens dark pink- resembling puff balls; The pods elongate, to 20-24 cm long, they are thick but compressed close and have a black, pulpy interior. They contain numerous seeds within.

S. saman has a wide range of useful products, the pod in particular producing an edible pulp. When ripe, the pulp is sweet and sugary. It can also be dried and ground into a meal for animal feed. The timber is strong and hard, with a rich, dark color, and makes good furniture. The heartwood is a dark walnut to dark chocolate brown which turns light to golden brown with darker streaks when seasoned; the sapwood is thin and yellowish and clearly differentiated from the heartwood. Texture medium to coarse; luster medium; either straight or cross grained; without distinctive odor or taste. It valued greatly for furniture, cabinet work, millwork, decorative veneer, joinery and wooden bowls.

The Hawaiian common name, 'monkey-pod', is used here because it is a logical derivation of the scientific name Pithecellobium (monkey earring in Greek). Besides monkey-pod, raintree, and saman, which is its name throughout Latin America, the tree is called mimosa in the Philippines.

Here is a further list of names for this tree:
Dormilon (Puerto Rico), Algarrobo (Cuba, Mexico, Guatemala), Cenicero (El Salvador, Costa Rica), Samaguare (Colombia), Lara, Carabali (Venezuela), Huacamayo-chico (Peru), Monkeypod (Hawaii).

Additional information:

The tree has been shipped and grown in many global locations such as:

American Samoa (Tutuila), Commonwealth of the Northern Mariana Islands (Saipan, Rota), Federated States of Micronesia (Chuuk (Weno (cult.)), Kosrae (cult.), Pohnpei), Guam, Republic of the Marshall Islands (cult.) (Kwajalein, Jaluit), Republic of Palau (Koror).

In the Pacific: Fiji, French Polynesia (Tahiti, Moorea, Raiatea) (cult.), Hawaii, Niue, Papua New Guinea, Samoa, Tonga
It was invasive on Fiji, where it is reported to contribute 85% of the total volume of woody biomass per hectare in low-lying alluvial sites and river valleys in the drier zones of the major islands. It does not appear to be a serious problem in Micronesia, but has the ability to spread through native forest ecosystems, as exhibited in Hawaii and elsewhere.

Elsewhere: Australia, Christmas Island (Indian Ocean).

On a personal note, I am currently attempting to grow one of these trees as a bonsai.  I started it from seed, soaked it for 24 hours and planted it in loose, well draining soil. It sprouted after a week or so and now stands around six inches high.  It has a fast-growing root structure and I've already had to repot it in a larger pot.  The most interesting aspect is the fact that it is very active and finicky - as it closes its leaves whenever shaken, disturbed or watered.  If you enjoy bonsai or experimenting with trees this one is very rewarding.

References used to compile this information:

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