Voles will strip the bark, rabbits leave sharp angled cuts on branches above the snow, and deer will fray the tips of all branches they can reach.
The drawback for spring pruning is whether you mind losing the blooms for next year. A girdled shrub might need pruning near to the ground. A lilac bush that is pruned to the ground will grow back to produce flowers in the third year. Sap oozing from a cut signifies rising temps, lots of life activity, and rapid healing of wounds.
Jo Bjerke is a master gardener. She lives in Virginia, MN.