I have a lilac tree, I.e. Only one trunk coming up from ground. It has been among trees which have now been removed and the lilac is very straggly. It is in flower now and after it has finished flowering I’d like to prune it quite hard. Can I do this and still get flowers next year? How is the best way to go about it please?
Right after the plant stops flowering, cut back the blooms (to prevent them from going to seed) and prune back around one-third of the branches (no more than that). Start by removing dead/diseased stems and thin shoots (suckers) that are sprouting from the main trunk or the ground. Lilacs bloom on last year’s growth, but pruning right after flowering should permit new shoots to develop blooms for the next year. If you prune too late in the season, you will kill developing buds.
Is your plant a tree or a bush? For the purposes of pruning, it does not matter – these recommendations also apply to lilacs that look more like trees than bushes. However, it is important to know if your plant has been grafted, as cuts must be made above the grafts and rootstock shoots should be pruned off (as they will not produce the appropriate flowers).
We have a lot of information already posted to our website about pruning lilacs, including:
- Pruning lilac: this also contains a few good links that provide more detailed information.
- “Pruning lilacs – how and when to prune lilacs”
Finally, Professor Leonard Perry of the University of Vermont, in his “Pruning lilacs properly” sets out clear “do’s and don’ts” for pruning lilacs.