I’ve been trying to shape up an old stand of lilacs for the last three or four years.
As you can see, they had gotten very leggy — and unproductive. Fewer and fewer blooms every year.
After they bloom each spring, I’ve been cutting back about one-third of the old woody stems every year. If you take out more than a third of the plant all at once, you may kill it.
Here’s how the whole stand looked after pruning a few weeks ago. You want to have new growth and foliage from the ground up, not just at the top. By cutting back the top of the plant, you encourage new shoots from ground level.
By doing this, you also let more air and light in, for better circulation and less powdery mildew.
Ideally, you want to prune lilacs (and most other spring-flowering shrubs) within six to eight weeks after they bloom. Otherwise, you’re cutting off next year’s flowers. The buds for next spring’s flowers begin to form this summer.
I had to take a saw to this guy.
Here’s my discard pile. Don’t be afraid to be pretty aggressive with lilacs.