Pruning a Red Sunset maple serves to maintain a well-structured plant. One upright central leader branch defines the trunk and tree's top tip. Rubbing or inward-growing branches are removed as are branches with crotch angles less than 30 degrees.
The worst times to prune are from midsummer to winter's start. New growth doesn't mature in time before fall frosts occur and wounds exposed in fall's cool and moist weather don't callus and heal properly. The best time to prune is late winter to midspring.
Canker and bark diseases occur more often after severely cold winters, advises the Barlett Tree Research Lab. Never prune into the swollen collar at the base of branches leading into the main trunk. Make the cut just outside this collar neck. Dead branches can be pruned away any time of year.