I have a Magnolia tree that is planted next to our house. This year, there were not very many blooms and the tree is getting rather bushy-looking. When is the best time to prune it and how much can be pruned?
According to the American Horticultural Society’s book, Pruning and Training by Christopher Brickell (DK Publishing, 1996), mature Magnolias should not be pruned unless it is essential. Many species will bleed from pruning wounds, and should only be pruned from summer to before midwinter. Summer-blooming Magnolias can be carefully pruned to reduce size by removing selected branches. The book Pruning: A Practical Guide by Peter McHoy (Abbeville Press, 1993) recommends doing this in late fall or early winter.
Below is a link to an interesting discussion on the how and why of pruning a Magnolia, from University of British Columbia Botanical Garden’s online forum.