Tree-Form Lilac – Pruning

Q: Online guides say that you can cut main limbs of a lilac to the ground to
encourage new growth. My tree-form lilac is ten feet tall but I want it to be
lower and bushy. 

A: I would wait until late February, just when the weather is getting a little
warmer, and make a pruning cut two or three feet from the ground. That’s the
time you’re most likely to get re-sprouting from dormant buds. After sprouts
emerge, clip off the growing tip of each one when it is twelve inches long.
That should result in a more attractive and bushy plant.