The balsa wood tree, scientifically named Ochroma lagopus, is a relatively fast growing plant found primarily in Central and South America. These trees grow best under the conditions found in rainforests, ideally in mountainous terrain between rivers. The country of Ecuador is perhaps the largest exporter of the wood, although many local farmers consider the plant to be little more than a weed.
Balsa is one of the lightest varieties of wood available, but not the absolute lightest. It is remarkably strong for its weight, however. Originally, the US military sought out balsa wood as a substitute for cork during World War I, but it soon proved more useful as a lightweight construction material for gliders and shipping containers. Hobbyists also began to work with it because it could be carved easily with standard woodworking tools and bent into a number of shapes without sacrificing strength.
Unlike some "crop woods" such as pine, balsa traditionally has not been grown in large groves or stands. The trees propagate much like dandelions — seeds are attached to soft tufts and carried off by the wind. If the seed lands in an area without direct sunlight, such as the dark canopy of the deep forest, it simply won't grow. A few lucky seeds may land in a sunlit patch or field and germinate, often to the chagrin of the farmer who owns the property. Balsa trees grow rapidly during their first five years, providing some shade to other plants with their oversized leaves.
The ideal balsa wood tree for harvesting is between six and ten years old. After ten years, the inner core of the tree begins to rot and the outer layers become useless. The tree is naturally fortified by water stored in large cells.
There may only be one or two balsa trees in an entire acre (0.4 hectares) of land, so harvesting is usually performed by one or two native workers with axes and carving knives for bark removal. The hewn trees are carried to the river and bundled for easier water transport to the processing plant. Barges carry the trees all the way to ports in the United States.
Raw balsa wood has a high moisture content, so it must be dried in a kiln for at least two weeks before it can be used commercially. The drying process creates an ultralight wood that is usually cut into sheets or round dowels. It does have a grain, so consumers should be aware of what type of cut they need for a specific project. Some is cut across the grain, which makes it suitable for carving but not for weight-bearing struts. Many people may remember the toy balsa airplanes sold in stores, so it is easy to imagine how fragile this wood can be.