Lilac Pruning
Lilacs need a balance of new shoots and older stems to achieve the most prolific blooming. In general when a stem reaches a 2” diameter, it should be pruned. If you are diligent with annual pruning your lilacs will flower throughout all branches.
When to Prune Lilacs
Pruning is not required until large cultivars reach 6’ tall. Dwarf varieties will not require pruning until they are 4-5 years old.
When they have reached that maturity, they should be pruned immediately after the blooms fade. Lilacs set their buds for the next season blooms almost immediately after blooms, so waiting will sacrifice next year’s blooms.
Lilac Maintenance Pruning:
Cut no more than one-third of a shrubs stems each year. This will keep the plant rejuvenated. Begin by pruning any dead or diseased stems, clean pruners with a rubbing alcohol. Finish pruning pencil thin suckers or twiggy growth, then prune any stems larger than 2” in diameter, prune any branches that cross or rub together.
Lilac Shaping:
Hand pruners are preferable to an electric pruners. Always prune shrub back to an outward facing bud.