Balsa, (Ochroma pyramidale), also called balsa tree, fast-growing tropical tree in the mallow family (Malvaceae), noted for its extremely lightweight and light-coloured wood. Balsa can be found from southern Mexico to Bolivia and is a common plant throughout much of its range. The 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 used as stuffing for mattresses and cushions. Balsa has pale bark and, like many tropical trees, has no annual growth rings. It can grow more than ....