How to Prune Lilac Suckers

Long-term Lilac Pruning

Suckers grow from the roots of the plant and are tricky to remove. Left alone, they will grow into a new tree. Disturbed, they will react by putting out even more suckers. Once your lilac is firmly established in a sunny, well-draining spot in fertile soil, it will happily grow and blossom for centuries. A lilac can become a family heirloom. It can also become a voracious nuisance, gobbling up the landscape. One method for pruning is to clip replacement suckers below ground during annual summer pruning. This works best on small or slow-growing lilacs. Leaving a few suckers allows new woody stems to form that will eventually produce more flowers.

Get to the heart of a riotous sucker problem by removing the suckers from the roots. Don't clip them or use shears. Dig down to the root and tear the sucker away from the root, getting as much of it as possible. The sucker produces dormant basal buds which will simply regrow if you don't tear or scrape them out. You will end up with even more suckers than you tried to remove in the first place. That's the plant's survival technique, and you will need persistence to overcome it. But do keep at it because too many suckers can compromise the vigor of the main plant.

If you've torn away the suckers and they've sprouted up again, it's time for more drastic action. Prune the root -- just cut it away from the tree -- to remove the sucker. This isn't as cold-hearted as it sounds. The severed root and sucker will grow a new tree. Plant it in another part of the yard and have more lilacs each spring or give it to a friend -- with careful sucker pruning instructions, of course. Don't sever too many large roots that are growing suckers at once or you could harm the tree.

If you have the room and love lilacs, let the suckers grow up. You may want to prune some of them so the plants don't become too dense. A thick mass of branches doesn't allow enough light to the center of the plant so it will eventually stop producing blooms. But allowing the suckers to grow in a pattern, along a garden wall, for instance, could result in a stunning landscape feature. Try pruning the roots in a circle around the tree by breaking them with a sharp flat shovel and carefully applying herbicide to the roots and suckers outside the circle.

Dig up the tree. Removal of a rampant lilac tree may be the only way to counter a serious sucker overgrowth. Cut the entire tree down, rip off all suckers on the remaining stump and treat the stump and immediate surrounding area with herbicide. Be careful not to get herbicide on or near any plants you want to keep or it will kill them, too. There are root killers and weed killers that will not harm lawns. Use this as a last resort -- lilacs are a beautiful addition to your garden, and toxic chemicals are not. If you do remove the tree and fail to treat the stump and surround, you will probably see more suckers grow back in the same spot.