Perennials are defined as a plant living for at least two years, differentiating from short-lived annual plants. The term is also used to distinguish plants with little or no woody growth like trees and shrubs. Perennials will typically grow and bloom in the spring and summer, die back in the fall/ winter and then return again in the spring.
Depending on the local climate, a plant that is a perennial in its native habitat or in milder conditions may be treated as an annual in cooler, harsher conditions. Perennials often have extensive root systems which help to prevent erosion and capture dissolved nitrogen before it gets into ground and surface water. Perennials are often better competitors than annuals in poorer conditions as the development of a larger root system allows better access to water and soil nutrients deeper in the ground.