Posted: 07/01/2015 at 19:24
Hi eddie, now is perfect but it depends on why you are pruning. A few tips:
Winter pruning will encourage growth, so prune young apple trees now to help develop their shape. The harder you prune weak growth, the stronger is will grow in the coming year, so if a tree is weak on one side prune that side back more (but don't reduce branches by more than about 50%.)
Late summer pruning will help to restrict growth, so only prune branches which are too vigorous then. Once an apple tree has grown to the size you want, this is the only time you should prune it.
I made a pretty comprehensive post about apple tree pruning a year or two ago which some members found helpful. I'll try and find it and will post the link.