When is the best time to prune shade trees?
February through March is generally regarded as the best time to prune most deciduous trees. The absence of foliage at this time of year gives the individual a clear view of the tree and allows the selection and removal of appropriate branches. Also, the walling-off or compartmentalization of wounds occurs most rapidly just prior to the onset of growth in spring. Oaks are an exception. The winter months – December, January and February – are the best time to prune oak trees.
Large amounts of sap often flow from pruning cuts on maple, birch, and elm when pruned in late winter. However, the loss of sap doesn’t harm the trees. The trees won't “bleed” to death. Eventually the flow of sap will slow and stop.