Agave (century plant). These plants are natives of the Western Hemisphere and belong in a separate family, the Agavaceae. The common name, century plant, refers to the tardy bloom of Agave americana, but that they bloom only when a hundred years old is fallacious. It is said that they flower when six years old in their own native habitat, but as conservatory plants perhaps 50 years are needed. Curiously enough they die after flowering.