It's best to prune established Apple trees in the summer as
this will help the development of shoots that go on to bear fruit. Summer
pruning also helps keep the tree in shape before it has a chance to thicken and
become harder to work with.
Pruning Advice from Keith Archer - Tree Surgeons in London
Cut back the leading shoots of every branch by half their
length to help the growth of side shoots. Only prune the current season's
growth, cutting to just above a leaf.
Then cut back all remaining side shoots to two or three
leaves from the bottom of the current season's growth, just above the bud.
