Each year, the spring and summer seasons seem to go faster and faster, and 2024 is no exception. If you have a lilac shrub, you can probably still imagine the sweet fragrance and beautiful flowers from a few months ago. I get several questions each year about lilacs, so the blog today is going to answer some of those inquiries!
A few years ago, we decided to begin excavating for our new garage in late summer, and unfortunately, had to move a lilac shrub. The transplanting was not as high of a priority as it should have been, and the shrub suffered tremendously the following year. We gave it a season to see if it would recover, but ultimately, it was too damaged. At that point, we decided to try rejuvenation pruning and cut everything back to 6” above the soil line in hopes that the shrub would come back and have a better overall shape and appearance. We had nothing to lose as the plant was suffering, not growing, and not flowering.
Question: What is rejuvenation pruning?
Answer: Lilac rejuvenation pruning involves cutting the entire woody shrub back to a few inches above the soil surface. This can be done if a shrub is really scraggly or if you want to change its shape entirely. Last summer, my parents had to do a construction project behind their very large, 20+-year-old white lilac, and they had to cut it back to the ground. It seems to be rebounding just fine, though!
University of Nebraska-Lincoln Extension guidance recommends doing rejuvenation pruning in late winter or very early in the spring.
Question: My lilac has not bloomed for the last several years. What could be wrong? It used to be beautiful each spring!
Answer: Lilacs need full sun to bloom. Often in people’s landscapes, as trees mature, lilacs get less sun than they once did, leading shrubs that once produced abundant, full blooms to have limited to no blooms.
Question: Why did my lilac bloom in the fall?
Answer: Environmental stress can cause out of season blooming. Some examples include drought, excessive heat, defoliation from pests, heavy pruning, insects, or diseases.
Question: What time of year should I prune my lilac?
Answer: Many spring-blooming, woody shrubs will set the flower buds for the next season’s growth in late spring or early summer, so be sure to prune for shaping and maintenance purposes as soon as the shrub is finished blooming for the current growing season.
For more information on lilacs, see the Home and Garden Information Center’s page, Lilac: Identify and Manage Problems — particularly the sections on diseases, insect pests, and heat-tolerant and powdery mildew-resistant varieties.
Remember, you can always contact your local University of Maryland Extension office or use Ask Extension to get answers to all your gardening questions.
By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.
I have read that we are farther south than they prefer, so already marginal before global warming; now it will be tougher for them here. The other thing I remember is that they tend to develop naked legs, less blooming on older wood, and older trunks are more susceptible to borers. Consequently, regular removal of oldest trunks with replacement by new suckers (but removing most of them) will provide the best results.
Oops. I did not notice that the writer is from the higher elevations in MD’s NW corner, so surely a great place for lilacs. Those of us closer to the Bay are more likely to struggle.