A perennial plant or perennial (Latin per, "through", annus, "year") is a plant that produces flowers and seeds more than one time in its lifespan, and therefore lives for more than one year. This term is usually applied to herbaceous plants or small shrubs rather than large shrubs or trees, but used strictly it also applies to all plants which flowers and produces seeds more than once.
Plants that flowers and produces seeds only once in its lifetime are called 'monocarp' as annual plants, which flowers in its first living year, then dies, or biennial plants, which only live for two seasons. Some monocarp plants can live for many years before flowering (and dying) as bamboo and agave.
Herbaceous perennials are plants that do not form permanent woody tissue. In warmer and more clement climates they may grow continuously. In seasonal climates, their growth pattern is adapted to the growing season. In cooler temperate regions they generally grow and bloom during the warm part of the year, and the foliage dies back every winter. Regrowth is from their existing tissue or root-stock rather than from seed, as with annuals and biennials.
In some cases, these perennials may retain their foliage all year round, even in seasonal climates. Herbaceous perennials that retain their foliage all year round may be called evergreen perennials. Others are called deciduous.
Examples of evergreen perennials;
Examples of deciduous perennials;
Woody perennials (ie. trees and shrubs) retain their woody structure permanently, but may lose their foliage in seasonal climates.
Perennial plants dominate most natural ecosystems. For example, grasses and most forbs on the prairie are perennial. Wild perennial plants are usually better competitors than annual plants, especially under resource-poor conditions. This is due to larger root systems which can access water and soil nutrients deeper in the soil and to earlier emergence.
There are many perennial plants important to human food production including most fruit and nut trees.