Why do leaves fall off trees in fall?

Why do trees lose their leaves in the Fall?

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...

My fiance and I are getting married next year. Everything is going to be fall colors - the bridesmaids will wear crimson and burnt orange, the flower girl will throw fall leaves instead of flower petals, the centerpieces will be fall foliage, etc. We...

I planted 4 maple trees in fall they all looked good with leaves in fall 1-2 in trunks. I used the old soil to fill in the hole and did not fertilize. I watered once a week until it started to get cold. They all dropped there leaves now this spring only...

I'm looking for a table giving the average date of leaves falling off trees (or leaves turning color) by year, averaged over North America, or for any specific location in the US. Thank you!