Bamboos are giant, fast-growing grasses that have woody stems. They are distributed in tropical and subtropical to mild temperate regions, with the heaviest concentration and largest number of species in East and Southeast Asia and on islands of the Indian and Pacific oceans. A few species of bamboo belonging to the genus Arundinaria are native to the southern United States, where they form dense canebrakes along riverbanks and in marshy areas.
The woody, hollow aerial stems (culms) of bamboo grow in branching clusters from a thick underground stem (rhizome). The culms often form a dense undergrowth that excludes other plants. Bamboo culms can attain heights ranging from 10 to 15 cm (about 4 to 6 inches) in the smallest species to more than 40 m (about 130 feet) in the largest. Mature bamboos sprout horizontal branches that bear sword-shaped leaves on stalked blades; the leaves on young culms arise directly from the stem. Though the culms of some species grow quickly (as much as 1 foot [0.3 m] per day), most bamboos flower and produce seeds only after 12–120 years’ growth, and then only once in their lifetime.