balsa

/bawl"seuh, bahl"-/, n.

1. a tropical American tree, Ochroma pyramidale (lagopus), of the bombax family, yielding an exceedingly light wood used for life preservers, rafts, toy airplanes, etc.

2. a raft made of balsa wood.

3. any life raft.

[1770-80; < Sp: boat]

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Tree (Ochroma pyramidale, or O. lagopus) of the bombax family (Bombacaceae), native to tropical South America and noted for its extremely light wood, which resembles clear white pine or basswood.

Because of its buoyancy (about twice that of cork), balsa has long been used for making floats for lifelines and life preservers. Its resilience makes it an excellent shock-absorbing packing material. Its insulating properties make it a good lining material for incubators, refrigerators, and cold-storage rooms. Because it combines lightness and high insulating power, it is a valuable construction material for transportation containers for dry ice (solidified carbon dioxide). It is also used in the construction of airplane passenger compartments and in model airplanes and boats.

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▪ tree

      common, fast-growing tropical tree, occurring from southern Mexico to Bolivia, that is noted for its extremely lightweight and light-coloured wood. Balsa has pale bark and, like many tropical trees, has no annual growth rings. It can grow more than 5 metres (16.5 feet) per year in full sun, reaching a maximum height of about 30 metres (100 feet). The large leaves, generally concentrated at the ends of branches, are pointed at the tips and heart-shaped at the base. Balsa trees flower at three to four years of age, and the solitary white flowers are usually bat-pollinated. The fruit is a capsule resembling a rabbit's foot (hence the specific name lagopus); it contains many seeds with long hairs that allow the seeds to be dispersed over great distances. (See rainforest ecosystem sidebar, “Flying” Trees.) The seeds remain viable in the soil for many years and may germinate after a burning occurs or a gap opens in the forest canopy. Balsa may occur in mixed or pure-species stands and in mature forest, where shade and slower growth result in a denser wood.

      Balsa wood has long been used in many commercial applications, such as model-building, packing, and insulation, and also in flotation devices (balsa is Spanish for “raft” or “float”). The seed fibre is also used as stuffing for mattresses and cushions.

      The balsa tree is related to the durian and kapok; all are members of the hibiscus, or mallow, family (Malvaceae).

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