If left to continue growing, the new wood being grown on the outside layers becomes very hard and the tree begins to rot in the center. Unharvested, a balsa tree may grow to a diameter of 6 feet or more, but very little usable lumber can be obtained from a tree of this size. The basla leaf is similar in shape to a grape leaf, only a lot bigger. When the tree is young, these leaves measure a much as four feet across. They become progressivly smaller as the tree grows older, until they are about 8 - 10 inches across.
Balsa is one of the few trees in the jungle which has a simple leaf shape.
This fact alone makes the balsa tree stand out in the jungle. For instance, in an area of the jungle that has been ravaged by a tropical storm or other natural disaster, the balsa trees will quickly sprout and begin to shoot up to impressive heights in a very short time. Their fast growth, and the extra large leaves they have in their early years, provide shade to the young seedlings of the slower-growing forest giants. By the time the seedlings are established enough to take care of themselves, the balsa tree is beginning to die. While nature intended the balsa tree to be a short lived nursemaid, mankind eventually discovered that it was an extremely useful resource.