The length of time a plant can live depends on the species. There are three classifications for the length of a plant's life span: annuals live one growing season, biennials live two growing seasons and perennials live more than two growing seasons.
An annual plant species completes its life in one year or less, meaning that it germinates, or begins growing; produces vegetative growth such as leaves and stems; flowers; sets seed; and dies in one year. Examples of annual species include lettuce and marigolds.
A biennial species completes its life cycle in two years, or seasons. During the first season, the plant is only vegetative, which means it has leaves and stems. During the second season, it produces flowers, sets seed and dies. Examples of biennial species are carrots and onions.
A perennial species completes its life cycle over many years. It may not flower or set seed for several years while it is growing in the vegetative stage, but once mature, it produces flowers and sets seed many times over the course of its lifetime. Examples of perennial species include woody plants such as trees. Some of the oldest trees have been known to live about 5,000 years.