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perennation The survival of biennial or perennial plants from one year to the next by vegetative means. In biennials and herbaceous perennials the aerial parts of the plant die down and the plants survive by means of underground storage roots (e.g. carrot), rhizomes (e.g. couch grass, Solomon's seal), tubers (e.g. dahlia), bulbs (e.g. daffodil, snowdrop), or corms (e.g. crocus, gladiolus). These perennating organs are also frequently responsible for vegetative propagation. Woody perennials survive the winter by reducing their metabolic activity (e.g. by leaf loss in deciduous trees and shrubs).