Lehdenlähtöön

Lehdenlähtöön is a Finnish term that translates literally to "leaf departure" and refers to the phenomenon of deciduous trees shedding their leaves. This is a natural and vital process for many plant species, particularly those in temperate climates. The shedding of leaves is a response to environmental changes, primarily the shortening of daylight hours and the decrease in temperature that occur in autumn.

During the summer months, trees produce chlorophyll, the pigment that gives leaves their green color and is essential for photosynthesis. As days shorten and temperatures drop, chlorophyll production slows down and eventually stops. The green color fades, revealing other pigments in the leaves such as carotenoids (yellows and oranges) and anthocyanins (reds and purples), leading to the vibrant fall foliage often observed.

The detachment of the leaf from the stem is facilitated by a specialized layer of cells called the abscission layer, which forms at the base of the leaf stalk. This layer weakens over time, eventually causing the leaf to fall. The purpose of lehdenlähtöön is multifaceted. It conserves water during the colder, drier months when the ground may be frozen and water uptake is difficult. It also prevents damage from snow and ice accumulation, which could break branches if the leaves were still attached. Furthermore, by shedding leaves, trees can reduce their metabolic activity during winter, saving energy. The fallen leaves decompose, returning nutrients to the soil, which will benefit the tree in the following growing season.