A perennial plant or perennial (Latin per, "through", annus, "year") is a plant that lives for more than two years. This term is usually applied to herbaceous plants or small shrubs rather than large shrubs or trees, but used strictly it also applies to the larger and longer-lived species.
Herbaceous perennials grow and bloom during the warm part of the year. They generally die back every winter. They grow back in the spring from their root-stock rather than seeding themselves as an annual does.
Woody perennials (ie.trees and shrubs) do not die back to the ground during the winter.