How and When to Prune Lilacs

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A garden expert tells us the best way to prune lilacs and enjoy their spring flowers. Also learn why your lilacs are not blooming.

when to prune lilacs

Lilacs are popular shrubs for their fragrant colorful blooms. Many gardeners wonder exactly how and when to prune lilacs. Ken Kuhnen of Machesney Park, Illinois, wrote in, asking, “My lilac tree is beautifully shaped, but I need it to be smaller. Where do I start?”

When to Prune Lilacs

With any type of lilac, you should only prune branches right after the flowers fade to enjoy maximum spring color the next year.

New lilac buds sprout from old wood. So if you start snipping in summer, fall or in spring before they bloom, you’ll cut off the forming buds. Note that different perennials have different pruning needs, so do your homework before you start pruning.

How to Prune Lilacs

To make your plant a little shorter, remove several of the larger stems to ground level. This will encourage new growth at the base of the plant. Reduce the height by no more than one-fourth of the plant each year.

Here’s exactly how you should do it:

Make cuts above an outward-facing branch or healthy buds. Repeat this process over the next few years and you will have a shorter plant with greenery from the tip of the stem to ground level. Cutting the whole plant back to the ground can result in a larger plant than you started with. That means even more pruning to achieve your desired results.

lilac shrub

Why Is My Lilac Not Blooming?

“I was given a small lilac bush years ago from a friend’s garden,” writes Georgette Jahn of Dingmans Ferry, Pennsylvania. “Every spring I’m so disappointed to see no flowers. Why is my lilac not blooming?”

Shade and improper pruning can prevent lilacs from flowering. Lilacs flower best with at least six hours of direct sunlight. Consider moving the bush to a sunnier location.

Too much high-nitrogen fertilizer and improper pruning can also result in a lack of flowers. Go easy on the fertilizing, and prune only if needed right after the lilacs should have bloomed. These plants develop their flower buds in the summer, and the buds open the following spring.

Lilacs are a great option to add to your garden. With a little work, they can add a beautiful pop of color.

Do you really love lilacs but wish they bloomed longer? Check out the new reblooming lilac options out there, like Bloomerang Purple from Proven Winners.

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Melinda Myers
Nationally known gardening expert, TV/radio host, author, columnist and speaker.