Answer: There are a number of contradictory cautions about pruning magnolias. That's because we prune an evergreen Magnolia much differently than how we prune a deciduous Magnolia. The evergreens will respond to conventional pruning and shaping, even shearing in some cases, whereas most deciduous simply will balk at such methods.
The main difference is that evergreens will grow back from the tips of the branches once cut but a deciduous in most cases will not respond at the terminals at all but may send out new growth up to a foot or more below where the cut was made
depending on the form and sometimes the variety of deciduous Magnolia.
Ideally, we want a nice full head on our evergreen Magnolias if we can get it or we at least settle for some sense of shape or we can have an upright, spreading form. If left alone the trees will more likely, depending on whether they are common forms
of Southern Magnolia or not, develop into an upright, spreading form. Round headed shaped trees here have been popular but they will require pruning to shape them when they are young and later or severe pruning when they are older with intermittent shaping about once every year or two.
We generally leave a deciduous Magnolia alone, leave it like it is unless we have to prune it or we want a particular shape such as giving a Star Magnolia a nice, round headed shape but that takes a while longer to accomplish than dealing with an evergreen Magnolia. With some forms of deciduous Magnolias a round headed tree is
just not going to happen no matter what we do.
So, keeping in mind that your southern magnolia may not respond precisely as you expect when pruning, you can still safely remove about one-third of the live plant material without compromising the health of your tree. When you prune, you may stimulate additional growth lower down on the trunk. If this begins to happen, rub out the buds or shoots as soon as they appear. You may have to continue to do this to discourage growth low on the trunk. But, if you keep at it, you'll eventually have a tree rather than a shrubby magnolia.
Best wishes with your landscape!
Q&A Library Searching Tips