“How long should you let your lilac bush grow after planting before starting to trim and shape it the way you want?” Question from Traci of Ithaca, Michigan

Answer: It all depends on your size preference for your lilac. Aside from pruning off dead or damaged branches or spent blooms, you can select prune your lilac to meet the desired height and to remove unwanted suckers at any time, so long as your plant is robust and growing well. “Select pruning” means taking away ungainly, unproductive, or overgrown branches for plant health and to reach the desired shrub size. You may cut branches all the way down to the ground or partially cut them to meet a specific height. Never shear a lilac! (Click here for a full lilac-pruning guide.)

Common lilacs (Syringa vulgaris) reach can between 8 to 15 feet. Most gardeners plant them in areas where they have lots of space to grow and don’t start select pruning until they are at least 6 feet. Shrubbier lilacs, like the Korean lilac (Syringa pubescens subsp. patula), may reach between 4 to 10 feet, and most gardeners don’t start select pruning them until they become quite robust and bushy.

The best time to prune a lilac is in early summer, right after they flower. This is because they set new flower buds shortly after flowering, and you don’t want to cut away next year’s blooms!

I hope this helps. Happy lilac pruning!

Jessie Keith

Black Gold Horticulturist