Cross Section of Cells of a Bamboo Stem on a Microscope Slide
Unlike all trees, individual bamboo culms emerge from the ground at their full diameter and grow to their full height in a single growing season of three to four months. During these several months, each new shoot grows vertically into a culm with no branching out until the majority of the mature height is reached. Then, the branches extend from the nodes and leafing out occurs. In the next year, the pulpy wall of each culm slowly hardens. During the third year, the culm hardens further. The shoot is now considered a fully mature culm. Over the next 2–5 years (depending on species), fungus begins to form on the outside of the culm, which eventually penetrates and overcomes the culm. Around 5–8 years later (species- and climate-dependent), the fungal growths cause the culm to collapse and decay.
This brief life means culms are ready for harvest and suitable for use in construction within about three to seven years. Individual bamboo culms do not get any taller or larger in diameter in subsequent years than they do in their first year, and they do not replace any growth lost from pruning or natural breakage. Bamboo has a wide range of hardiness depending on species and locale. Small or young specimens of an individual species produce small culms initially. As the clump and its rhizome system mature, taller and larger culms are produced each year until the plant approaches its particular species limits of height and diameter.