Deciduousness

Deciduousness is the seasonal shedding of leaves by a plant, typically trees and shrubs, as a strategy to cope with adverse environmental conditions. It involves the selective abscission of foliar tissue at specialized regions called the abscission zones, usually near the base of the petiole. Before abscission, leaves often undergo physiological changes that withdraw nutrients and water, and a protective layer forms to prevent damage after shedding.

Timing and triggers vary by climate. In temperate regions, many deciduous species lose leaves in autumn in response to shortening daylight and cooling temperatures. In tropical regions, leaves may be shed during prolonged dry seasons or periods of drought. Some species, including certain conifers such as the larch (Larix), are deciduous as well, shedding needles rather than broad leaves. Partial or staggered shedding can occur in some species, particularly those with mixed-age shoots or varied microhabitats.

Functions and ecological significance include water conservation, reduced energy expenditure during unfavorable seasons, and protection against damage from freezing, snow load, or drought. Leaf fall also resets the carbon balance for the next growing season and contributes to nutrient cycling through leaf litter that enriches the soil.

Variation exists among species in the degree and timing of deciduousness, and environmental conditions influence its expression. The term derives from Latin deciduus, meaning falling off. Deciduousness is a common strategy in many temperate and tropical ecosystems, reflecting adaptations to cyclical resource availability.