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When Lilacs Won't Bloom

'Dark Knight' Lilac
For a complete guide to lilac care and planting, see the Lilac Planting and Care .

Lilacs are usually fairly reliable bloomers, but sometimes they fail to flower. Here are some tips to make sure yours bloom:

  • Usually, insufficient sunlight is the problem. A minimum of six hours of sun is needed each day.
  • Too much nitrogen can be a problem. Often lilacs are planted in the lawn and fertilizers used to green up lawns are high in nitrogen. For the lilac, this causes beautiful green foliage but little bloom. Avoid using fertilizers high in nitrogen.
  • Make sure you prune at the right time. In early spring, remove any dead or damaged wood. But don't do any major pruning because you can easily remove the dormant flower buds. After the flowers fade, it's OK to do more major pruning, such as reshaping or rejuvenation of an old bush. You can also remove the faded flowers. Just be sure to complete pruning before midsummer. If you wait too long, you risk removing some of the next season's blooms.
Reader's Tip
About 20 years ago I had just moved to a home in the suburbs of Portland, Ore. (in the spring). There was a small tree in the front yard, looking very lonely and unattractive. I soon recognized the leaves as a lilac, but no blooms that year. The next year it had grown, but still no blooms. Because it still looked unbeautiful, that fall I talked to it. Yes, I know that talking to your plants helps! But it's what you say that counts, and what I said was something like this: "If you don't bloom next year, your days are numbered!"
You guessed it, it bloomed and was a beautiful dark French lilac. Every year after that it bloomed, more profusely each year, and people would stop to ask where I got it. I am sure that it hadn't bloomed because it was just too small and wasn't ready, but I like to think that the "talking to" it got helped it along. So talk to your plants, and if they don't perform, warn them.
–Elizabeth, Yachats, Ore.
Another Viewpoint
I would like to add to the reader's tip about talking to your lilac bush.
Like her, we moved last spring to a home with an established lilac that had never bloomed. I explained my plant philosophy to the recalcitrant bush—"I will love, feed and cherish you as long as you in turn produce flowers (or fruit etc.)—otherwise, your spot will be given to something else."
The lilac is evidently a true adolescent and put out two flowers! So, does it stay or does it go? "OK bush, give me more than two flowers, or else!" And this year, there are three!
My tip: when you talk to your plant, be VERY explicit about the rules :-)
–Mary, Poplar Bluff, Mo.