I have a row of 5 beautiful espalier apple trees (Jonagold, Granny Smith and Gravenstein) that are about 4 years old, and they put out huge amounts of growth over the summer. I've been pruning the first growth back in late June, but when should I prune the growth from the rest of the summer? Is it better to do it in September when there's still light and the trees still have some leaves, or wait until mid-winter (February?) when they have lost all their leaves?
I'm north of 45 degrees latitude, so winters are dark, but we do not get down to freezing for more than a few days in the winter, and there is frequent rain.
I've read the excellent answers in this post When is it ok to prune an overgrown apple tree? but I'm not sure how I need to think differently about espalier trees.