Like other dwarf plants, dwarf lilac bushes are created by mounting a lilac bush on a rootstock, which prevents the lilac bush from growing to its full height. Dwarf lilac bushes are ideal for area in your garden where you have space for only a small plant, or for growing in pots or planters. Though dwarf lilacs may remain smaller than traditional lilac bushes, they retain the same properties of lilac plants, so the same pruning process used for standard lilac bushes can also be used for dwarfs.
Plan a shape for your lilac bush. While lilac bushes are often seen as rectangular or oval-shaped shrubs, the plants can be pruned into any shape you want, including a treelike form with one central branch. Knowing the shape you want helps you prune properly.
Prune immediately after a lilac bush blooms. This prevents the removal of the buds that form for the following growing season. If you prune the bush too late, usually after midsummer, the buds may be cut off the plant and the lilac bush may fail to bloom the next year.
Remove all the suckers if you want the bush to keep its current shape. If not removed, these suckers that grow from the bottom of the plant will develop into full, vertical branches, which will broaden the lilac bush. The bush will continue to grow larger with each new sucker.
Prune away the oldest branches first. If you choose to cut off full branches to reduce the size, select branches that have bloomed at least three years in a row. This gives the new branches time to establish and begin forming buds.
Cut off any branches that are diseased, insect-infested or dead. If a branch does not have any green near the collar where it is connected to the main trunk, it is dead.