I am aware that certain types of apple require another type to
pollinate, however is this solely a question of blossom time? In other
words will Apple A and B pollinate each other if they are in blossom
together? The reason I ask this is that I have a number of trees which
were carefully chosen in pairs for pollination. However due to the
vagaries of the weather they are not always in blossom together, hence
cannot possibly cross pollinate, though others, which are not paired are
blossoming together.