Ochroma pyramidale

Ochroma pyramidale, commonly known as balsa, is a large, fast-growing tree native to the Americas. It is the sole member of the genus Ochroma, and is classified in the subfamily Bombacoideae of the mallow family Malvaceae. The tree is famous for its wide usage in woodworking, due to its softness and its high strength compared to its low density. The name balsa is the Spanish word for "raft" and the Portuguese word for ferry. A deciduous angiosperm, Ochroma pyramidale can grow up to 30 metres (98 ft) tall, and is classified as a hardwood despite the wood itself being very soft; it is the softest commercial hardwood and is widely used because of its light weight. Balsa trees grow extremely quickly, often up to 27 metres (89 ft) in 10–15 years, and do not usually live beyond 30 to 40 years. In terms of volume (as opposed to height) they may be the fastest growing tree known; Streets mentions one individual which grew 11.2 m (37 ft) tall and 17 cm (6.7 in) diameter at breast height during a period of fifteen months. Balsa, like most rainforest trees, does not make annual rings, but this growth is equivalent to rings 7 cm (2.8 in) wide. They are often cultivated in dense patches, with Ecuador supplying 95% or more of the commercial balsa. The wood from these trees is highly valuable due to its high strength-to-weight ratio, which is achieved through a kiln-drying process that leaves the wood's cells hollow and empty. Balsa wood is popular for light, stiff structures in model bridge tests, model buildings, and construction of model aircraft. It is also used in wind turbine blades and in the manufacturing of wooden crankbaits for fishing, makeshift pens for calligraphy, composites, surfboards, boats, "breakaway" props for theatre and television, and even in the floor pans of the Chevrolet Corvette. Balsa wood played a historical role in Thor Heyerdahl's Kon-Tiki expedition, where it was used to build a raft. Balsa wood is also popular in arts such as whittling and in the making of baroque-style picture frames due to its ease of shaping.