I have a fairly mature (25') evergreen Magnolia (grand flora). I want to prune some of the limbs (not at the trunk), so the tree is not spread so wide, particularly lower branches. Is it too late to do that this year?
You can prune any time of year as long as you follow the general guidelines and remove 25 percent or less live wood. More generalizations include using sharp tools, removing a branch before it is 2 inches in diameter (large branches take longer to seal naturally); and don’t use so-called “wound sealer.” Occasionally cut branches will drip sap. Although many people refer to such activity as “bleeding,” it will not damage the tree or its general health.
I wasn't able to locate a good image that could guide you through the process. So, let’s use this illustration (pruning a walnut) to illustrate the placement for your cuts. (http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/ENVIRON/walnutpruning.html) Rotate the illustration to the left, then consider the upper most branch similar to one of the long side branches on your tree. Your cuts should be just beyond a side branch that is at least half the diameter of where the removed section is cut.
Consider hiring a Certified Arborist. (Such persons must pass a test and acquire continuing education.) You can locate a Certified Arborist in the Yellow Pages, online or the phone book under the heading of “Trees” or something similar. Or you can search with your zipcode at http://treesaregood.org/. Phone possible candidates, get their bids after on-site evaluations, then hire the one who you are most comfortable with.