For lilacs with a tree-like form, remove all suckers that appear at.

May 20, Pruning in the winter will remove all the bloom for the following spring. If your lilac is very thin and lanky, renovate it by removing the oldest branches gradually over two or three consecutive seasons, always in the late spring.

The lilac will grow back, but it'll take a season or two.

The first spring, remove about one-third of the old canes all the way down to the bushleaning.barted Reading Time: 2 mins. How to Prune Lilacs After Blooming. 1.

Dip the pruning shears, loppers or any other cutting tools in rubbing alcohol or a solution that contains 10 percent bleach and 90 percent water 2. Cut stems with spent blooms back to just above the highest lateral bud. 3. Cut branches and shoots back. Jul 08, How to Prune Lilac Bushes Regular Maintenance Pruning. The general shrub pruning rule is to cut no more than a third of the stems each year.

2  Rejuvenation Pruning. Older lilacs can have stems as thick as small trees and will flower only on the topmost branches. Working With Japanese Tree.