Why do leaves fall off trees in autumn?
Deciduous trees shed their leaves in autumn as a protective mechanism during the cold months of the year. In very cold climates, it is just too cold for the plant -the leaves freeze and cannot carry out their normal job of photosynthesis (making food with the help of the sun’s energy).
So, instead of having leaves hanging around doing nothing, the tree sheds them and goes into a kind of sleep – much like a grizzly bear hibernates.
In autumn, when the daily temperature or daylight hours decrease, the tree senses winter is just around the corner. In preparation for the cold, it shuts off the connection to the leaves, which then wither, die and fall off.