I always understood that the apple tree wassail was a sort of toast so that the tree would bear fruit the next year--that is, they actually sang to the tree(very Earth religion sort of thing.) In those days the words "hardy perennial" were obviously not in their vocabulary...I imagine this ritual was similar to "conjuring summer" which had to be done every spring to be assured that the warm weather would come. It's a good thing we don't live in such a state of uncertainty!