A plant that lives for a number of years. Woody perennials (trees and shrubs) have a permanent aerial form, which continues to grow year after year. Herbaceous (i.e. nonwoody) perennials have aerial shoots that die down each autumn and are replaced in spring by new shoots from an underground structure (see perennation). Lupin and rhubarb are examples of herbaceous perennials. Compare annual; biennial; ephemeral.