Dwarf lilac bushes require less pruning than standard-sized shrubs and trees. They should be pruned throughout the year. Items needed to prune a dwarf lilac bush include rubbing alcohol and pruning shears or loppers.
Disinfect the pruning shears or loppers
Disinfect the pruning shears or loppers by spraying or wiping them with rubbing alcohol. In addition, disinfect the tools after pruning each plant. When removing diseased branches, disinfect after each cut.
Cut flower heads and branches
Cut off old flower heads when one or two new shoots become visible. Cut above the new shoot or the bud. Cut branches with pruning shears or loppers to create the desired shape of the bush. Do not remove more than one-third of the stem. Make the cut above a bud that is facing the desired direction of new growth.
Encourage new growth
If the dwarf lilac bush is becoming old or bare at the base, cut the oldest stems back to the base of the bush. This method encourages the bush to put out new growth.
Remove dead or diseased branches, and prune back
Check the bush throughout the year for dead or diseased branches. Remove the branches by cutting just above a bud. Discard the branches after removal. In late winter or early spring, remove all but a few of the strongest and healthiest shoots growing from the plant's base.