How do trees know when to blossum?

Each year I see that trees and bushes of the same species blossum exactly at the same day in the whole country. Suddenly you see the hawthorn blossum everywhere. On the picture you see the old peartree next to our house. It was totaly neglected when we first came here. We pruned it thorougly the first year and now it blossums beautifull and it carries lots of pears in the fall. He blossums together with all his brother and sister pear trees at the same time. Do they communicate? I think that the native American Indians (and a lot of other native people, like the Australian and African tribes) are right when they say that everything that lives is bound by a great Spirit. Unfortunaly we lost the connextion with this Spirit. We look and listen to old grey men dressed in purple robes. We should listen more to the trees and the great Spirit in our harts. Then we would also know how and when to blossum, together with our brothers and sisters.