I've noticed that some maples will bloom after their leaves emerge and some oaks will bloom before their leaves emerge.
I know that many plants time their blooming so as to be the only thing blooming at that time - to reduce competition for natural pollinators.
I doubt that leaf emergent is dependent upon pollination because there may be reasons why pollination would not occur - ie heavy rain.
Trees store food reserves for the next year and make the buds prior to fall - that is how they can make flowers before leaves emerge.
One big mystery to me is how trees know it will be a wet summer and thus we end up with a Mast Year - when there are just massive quantities of nuts in most of the trees? That decision to go all out on nut making has to be made in the previous year and then that spring...
