deciduous

Deciduous describes plants that shed all or part of their leaves during a particular season. In temperate regions this shedding is annual, typically in autumn, as daylight and temperatures drop. In many tropical regions, trees shed leaves during the dry season to conserve water. The word comes from Latin deciduus, meaning “falling off.”

The shedding process occurs at a specialized leaf-abscission zone at the junction of leaf and stem. Hormonal changes—often a decrease in auxin and an increase in ethylene—trigger enzymatic breakdown of cell walls in the abscission layer, allowing the leaf to detach. Nutrients may be reabsorbed from the leaf before abscission, and chlorophyll degrades, revealing carotenoids and sometimes anthocyanins as the leaf changes color.

Deciduousness is an adaptive strategy that reduces water loss and metabolic cost when growing conditions are unfavorable. In cold climates it minimizes damage from freezing and reduces energy demanded by maintenance of leaves; in dry climates it lowers transpiration. Some species are only partially deciduous or may drop leaves irregularly, depending on environmental conditions.

Notable deciduous trees and shrubs include many temperate species such as oaks (Quercus), maples (Acer), beeches (Fagus), and birches (Betula). In tropical regions, many trees are deciduous during the dry season, with examples including teak (Tectona grandis) and various tropical hardwoods. This trait contrasts with evergreen plants, which retain leaves year round, and with semi-deciduous or semi-evergreen species that shed leaves intermittently.