Caring for Lilacs

Many plants benefit from pruning each year. Lilacs are no exception. However, it is typically desirable to time your pruning for just after the plants have bloomed to avoid cutting off next year’s flower buds. However, minimal amounts of pruning can be done at any time without sacrificing many blooms.

The first step in any pruning project is to make an assessment. Stand back and take a look at the shrub from all angles if possible. Determine what your overall goal is for the shrub and consider its age. Is it a new shrub in need of training or is it an older established shrub? Before removing any living branches, cut back any dead branches and reassess what is left. 

There are generally three routes to go when pruning a shrub. You can prune to train a younger shrub, prune to maintain, or prune to rejuvenate the shrub. When training a young shrub, minimal pruning is recommended. The focus should be on removing dead or broken branches as well as branches that are twisted around and/or crowding other branches. No more than 15% should be removed on young shrubs. Older shrubs, those 5 years old and older, benefit from regenerative pruning. This type of pruning addresses the legginess that is often associated with many types of lilac shrubs. The oldest branches should be removed to the ground rather than removing the new shoots. The new young shoots should be left in place. Twisted or crossing branches should be removed back to the branch collar. Minor shaping can be done to maintain a natural vase shaped habit. Finally, renewal pruning is typically reserved for those shrubs that have not received regular maintenance over the years. Usually, the shrub only has flowers at the tips of its branches. In this case, all the large, old branches are cut to the ground. It will likely take several years for the shrub to have flowers again. If the shrub is already in declining condition, the shrub may not recover from this type of pruning. 

Lilacs are some of the most beloved shrubs. They often bring back memories of wonderful fragrances and old homesteads. Starting a maintenance plan when they are young will keep your lilacs around for years to come.