August Lilac Bloom

Asked August 23, 2020, 2:31 PM EDT

One of our 25 year old lilac bushes did not bloom this spring, in fact it looked dead and I was about to cut it down. In the past two weeks it has started producing green leaves and this morning I noticed it is blooming, in August! Any ideas? Should I still cut it down so if it is diseased it does not spread?

Washington County Minnesota

2 Responses

Second blooms on spring-blooming woody plants are atypical, but not unheard of. For instance, some varieties of magnolias often bloom in late summer. It is less common on lilacs. There are reblooming lilacs on the market, but it sounds as if your specimen is not one of those. Our current weather pattern of a cool early August followed by the present hot and humid conditions is the likely cause of this situation. See

https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/lilac/branchesdeaddying

There are also a number of diseases that can affect lilacs. Study the links below to see if the conditions of your lilac are similar to any of those illustrated.

https://hortnews.extension.iastate.edu/lilac-pseudocercospora-leaf-spot

In any case, it may help to clear out leaf debris below your lilacs, so that any fungus or disease lurking there won’t affect next spring’s flower show. Discard or burn the debris; don’t add it to your compost pile.

Hopefully your lilac is just responding to unusual weather patterns, but study the illustrations of lilac disease (above links) to see if your plant falls within any of the descriptions or matches any of the photos. If so, follow the recommended actions for the particular condition.

Please let us know if you have further questions.


Thank you for your response.