What Happens to Leaves in the Spring?

Cold Requirement

• Trees and plants have a cold requirement -- a minimum number of days of cold temperature -- before their buds break open. The cold requirement varies among species. Northern species need more cold days while temperate and tropical species need fewer.

Buds

• Buds form in the fall in preparation for spring. The hardened bud is a protective casing for living tissues. When the cold requirement is reached, the temperature is warm enough for successive days and snowmelt increases water availability, the bud opens and the leaf it contains unfurls.

Spring Leaf

• Once exposed to sunlight, the leaf begins photosynthesis. The leaf takes in water and carbon dioxide, and converts them to sugar and oxygen with the energy from sunlight.