Lilac Trimming: Taming Our Overgrown Lilacs

Our lilacs were planted by the original owners sometime around the moon landing. They're 14 feet tall, mostly bare at the bottom, and the flowers are all up where only birds can smell them. Time for some lilac trimming.

When to trim lilacs

Right after they finish blooming. Lilacs set next year's flower buds on this summer's growth. If you prune in fall or early spring, you cut off next year's flowers. In Minnesota that means trimming lilacs in late May through June. We cut it close this year, but early July still works if you're quick.

Three kinds of lilac trimming

• Deadheading: snip spent flower clusters just above the next set of leaves. Optional, but it keeps the shrub looking tidy.
• Maintenance pruning: remove dead, crossing or rubbing branches, and suckers coming up from the base.
• Rejuvenation pruning: for overgrown lilacs like ours. Remove about one-third of the oldest, thickest stems at ground level each year for three years.

How we cut back our overgrown lilac

1. Picked the oldest canes, the gray, thick ones with few leaves at the bottom.
2. Cut them flush at the ground with a pruning saw. Loppers couldn't handle the 3" stems.
3. Left the younger, more vigorous stems to carry flowers next spring.
4. Thinned suckers, keeping a few healthy ones to become future main stems.

It looks a little sparse now, but in two years we should have a full, flowering lilac at nose height again. Patience is a gardening tool too.