I live in Woodbridge, just outside Toronto. I have a fifteen year old golden delicious tree which has never been pruned and is just a bit taller than my two storey house. When should I prune it and how much can I lop off? It is still loaded with apples. Thank you.
‘Golden Delicious’ apple trees have a naturally spreading habit, open-center form, therefore, when pruning, your goal is to keep that form open.
As the tree matures, it requires moderate pruning. You will notice that it bears its fruit on spurs (stubby branches). These need to be thinned to prevent overcrowding and to make way for new growth.
It is advisable to prune mature trees when it is dormant (late winter or early spring).
Lee Reich in his ‘Pruning Book’ advices also to fruit pruning: “Apples respond thankfully to a 5-in spacing, with no more than one fruit per flower cluster…and, each fruit needs the work of 40 leaves for nourishment.” This is done to ensure good fruit size and to prevent branch breakage. Apple blossoms often result in a bloom of cluster of 5 or 6 blossoms creating a heavier crop of fruit than the limbs can withstand. You can do fruit pruning when the apples are the size of a dime.
The Ecological Agriculture Department of McGill University put an extensive document on pruning apples, perhaps more than you want to read, however, it will show you drawings on how to prune ‘Golden Delicious’.: https://eap.mcgill.ca/CPTFP_7.htm
Lastly, please remember that with any shrub or tree, the golden rule is that you should never remove more than 1/3. Also, as your tree seems quite large, you may want to consider hiring a certified arborist who may have the correct equipment and experience with fruiting trees (always interview first).
Best of luck and hope you continue to enjoy your apples for years to come.