Sugar Maple (acer saccharum) is one of the great native trees of North America. Tolerant of shade or sun, it grows to a towering 80 feet and has been used as a residential tree for centuries. It is a hardy hardwood tree and its leaves present a stunning fall show, turning from yellow to orange, red and mahogany depending on its location. The only problem with this grand tree appears to be its intolerance of street salt. Pruning this fine shade tree requires a little knowledge and well-sharpened tools.
Remove dead branches or trim asymmetrical branches on young sugar maples. This strong-limbed tree generally needs little discipline its first few years. The U.S. Forest Service advises pruning “first for safety, next for health, then for aesthetics”. Although sugar maples may benefit from removal of lower branches to “raise the crown” and allow more air circulation, they will require little else until they are 10 to 15 years of age.
Prune sugar maples when they are dormant in late fall or winter, depending on location. Inspect trees carefully after storms and in late winter to get any clean-up done before the sap starts to run in very early spring. Remove dead or diseased branches any time. Sugar maple is susceptible to verticillium wilt. Anthracnose may cause problems in wet seasons.
Prune branches that grow into the center or rub against each other. Remove smaller branches up to two inches in diameter first. Sugar maple makes dense shade; removal of some branches in the center will let in sun and air. Cut small branches just outside the “collar”, the thick fold of bark at the junction of the branch and its lateral. Cutting “flush” to the main branch injures the collar and cutting too far out leaves a “stub”, both lengthening the healing time for the tree.
Remove branches that grow downward—they will eventually interfere with others and either rub against them, opening protective bark to insects or infections or block air flow in the center of the tree. “Lift” the crown when it grows too dense to allow air circulation underneath or makes lawn mowing awkward by removing lateral branches along the trunk beneath the crown.
Trim branches that extend beyond the natural symmetry of the oval “canopy” of the tree or droop over traffic or living areas. A sugar maple will grow 50 to 80 feet tall and spread 35 to 50 feet wide. Do not clip more than a third of the length of a branch off and never trim the “leader”—the central upward-growing branch of the tree.