Autumn and the trees-How do trees know that it is time for the leaves of the tree to change colors and fall?

Question

Have you always wondered how do trees know when it is that time of year for the leaves to change colors and fall off of the trees on to the ground,what processes must a tree go threw before it's leaves can start to change color and fall on to the ground.

5-10-08

Answer 1

As the seasons change....daylight hours becoming shorter and temperatures dropping, the sap in the trees recedes to the roots. The roots keep the tree alive through the winter. The loss of sap causes the color change and loss of the leaves. The trees don't really know, they merely react.