Although bamboo is a grass, many of the larger bamboos are very tree-like in appearance and they are often called "bamboo trees". The reason bamboos are so different from trees is they lack a vascular cambium layer and meristem cells at the top of the culm. The vascular cambium is the perpetually growing layer of a tree's trunk beneath the bark that makes it increase in diameter each year. The meristems make the tree grow taller.

A single culm (stem) of bamboo from an established rhizome (root) system reaches full height in one growing season, but then persists for several years, gradually increasing the number of side branches and branchlets, but neither growing broader or taller.

Some species of bamboo rarely flower, some of them only every 10-100 or more years. Some of these species are monocarpic, the plant dying after the seed matures. Furthermore, all the individuals of the species will flower at the same time in a large geographical region. This is thought to have evolved to reduce the effect of predators of the seed, who would be unable to depend on a predictable food supply.

Established bamboo will send up shoots that generally grow to their full height in a single season, making it the fastest growing woody plant. Several subtropical bamboo species can grow 30 cm (1 foot) per day, with some species having been documented as growing over 100 cm in one day. For the species most widely cultivated in gardens, 3-5 cm per day is more typical. A newly transplanted bamboo plant can take 1-2 years before it sends up new shoots (culms) and will have many seasons of "sizing up" before new shoots achieve the maximum potential height for that species.