Plants grow, reproduce, die or go dormant, and sprout again according to patterns that vary species by species. Most flowering plants fall into one of three categories.
Annuals live for only one year. A seed sprouts, usually in spring, grows throughout the warm weather, and flowers somewhere between early spring and late fall, depending on the species. As the flowers wilt, those that were pollinated begin to form seeds. Once the seeds are dispersed, the annual plant dies, with its genetic material now invested in the seeds. Seeds that are produced early in the growing season may germinate in late summer or fall, but most seeds go through a period of dormancy and sprout the following spring if conditions are right. Others may survive for years until they have adequate moisture, light, and soil to germinate. A large percentage of seeds are eaten by birds, humans, or other animals, while some rot, consumed by microorganisms.
Biennials have a two-year lifespan. The plant puts out leaves (but no flowers) in its first growing season. In the fall, the leaves either die back or, in some cases, persist throughout the winter. The plant’s energy is stored in the roots until spring, when leaves begin to grow again. In spring or summer, the plant puts up a stalk and produces flowers and then seeds. Once the seeds are ripe, the whole plant dies, leaving the seeds to carry on the next generation.
Perennials follow the same pattern as biennials, except the plant continues to live for several years. It flowers and sets seed each spring or summer, beginning with its second year, and goes dormant each winter, storing energy in its roots. By the time the aboveground parts have died off, the buds of next year’s stem, flowers, and leaves have already formed on the roots. If you dig down to the top of the root between late fall and early spring, you may find one of these buds. Dissect it carefully, and you will find miniature leaves and rudimentary flower parts inside its protective coat.
Deciduous trees and shrubs are perennials with leaves that die off in the fall, woody stems (trunks) that persist all year long, and a lifespan of many years. Like other flowering perennials, trees maintain just enough metabolism to stay alive in the cold. The energy to put forth new leaves and flowers is stored in the roots as well as in the buds, which formed on the twigs the previous summer. When the weather is warm enough, with periods of sunlight sufficiently long, the buds will swell, the embryonic leaves within will expand, the green leaves will manufacture food for growth, and the cycle will begin again.
Evergreens also follow a cycle of increased and diminished growth. The outward signs are less obvious but are observable. See the article Pines, Conifers, Evergreens.
