How to Trim Mature Lilac Bushes Without Killing Them
- 1). Cut down and remove all root suckers that grow from the rootstock and are away from the base of the plant. These will not produce flowers consistent with the rest of the plant.
- 2). Select one-third of the shoots to cut down, starting with the oldest. Cut these down to ground level. It is best to only cut down one-third of the plant each year, as lilacs only flower on wood that is about three years old.
- 3). Add compost, composted manure, or a balanced chemical fertilizer around the base of the plant and work into soil. Lilacs prefer a neutral ph balance in the soil. If your soil is acidic, you can add lime to sweeten it.
- 4). Repeat steps 1 through 3 for the next two years, so that after three years the shrub will be all new growth. During the yearly pruning, it is also important to trim and thin the new shoots.