I haave a 25 year old Magnolia tree in Cleveland, Ohio. It is close to my house and growing out of control. Can I prune this back drastically? And will it continue to grow then. I would like to cut 50% of height and width off of it. When is best time to do that, if possible.
Suggest that you consult a certified arborist. As the tree is large, close to your house, and the operation described is a major one, the expense involved would be worth it in terms of the tree's health and your own safety. Welcome to the Forum, fellow Buckeye!
One of the curators, who tends a lot of magnolias here, told me that magnolias do not respond well to pruning. Cuts into old wood usually do not heal well and often invite rot into the tree. One has to be very careful when pruning them. Such a drastic pruning as you are thinking might very well kill the tree. I would consult an arborist as togata suggests.