I received an email from one of our readers who has enjoyed my column for a number of years, and she asked whether she should prune her lilac now and how to do it properly.
Lilac has been among one of my favorite flowers for as long as I can remember. The lilac growing on the north side of my yard has been here for over 40 years.
I transplanted two other lilacs that were large enough to move from my mother’s home.
As a part of my heritage they came from my grandmother’s garden. I don’t believe that I shall ever forget Grandma’s bouquets of lilacs.
French lilac or (Syringa vulgaris cvs.) produces the most and abundant flowers on stems that are not more than 5 to 6 years old. As the stems get older, the flowers become smaller and more out of reach.
However, with proper pruning, a lilac can produce flowers reliably for decades. The technique you use depends on the age and health of the shrub or tree.
One of the qualities that I appreciate about lilacs is that they can tolerate severe pruning. If you can annually maintain lilacs, you will be able to regulate the height of the lilac and produce more flowers.
This should be a critical part of your decision-making when pruning.
Lilac should be pruned yearly to develop and promote vigorous growth, which enhances flowering and shapes the lilac to a traditional form. The 100-year-old lilacs at historic Wolcott Lilac Garden in Kent produce wonderful blooms after pruning.
Yearly pruning follows standard goals. When you cut out diseased stems, misshapen stems, damaged stems, and unproductive stems this is the first step. Following this step you have achieved the basic goals of pruning.
You also need to thin and remove selected stems to encourage properly spaced and vigorous growth.
New shoots or suckers that arise from the roots need to be reined in to keep them from straying too far from the center of the plant and to allow a few inches between each stem to avoid overcrowding.
Retain shoots that are pencil-thick all the way to the end of the branches because they will be the most productive. Small twiggy growth is usually not productive. and will not produce flowers.
Later in the season, you need to look at the plant and check whether there might be too much shade. These twiggy stems reveal this challenge. Twiggy stems need to be pruned soon after flowering.
Removing shoots and stems just above the soil level reduce the risk of soil-borne pathogens. Please keep in mind that the more branches you remove, the more blooms you sacrifice.
As part of the annual maintenance of the lilac, you will want to deadhead spent flowers off of your shrubs. This job should be done right away after the blooms are finished.
The old flower needs to be cut off at its base just above the two new shoots that angle out from the stem that ended with the old flower. New shoots will grow over the summer, set flower buds, and be topped off with a flower cluster the following spring.
As you would do this traditional thinning, removing the old blossoms allows more of the plant’s energy to be directed into growing vigorous shoots and flower buds. This annual work should be done in June.
As I have pruned lilacs in the past, every once in a while, I see a tall, vigorous shoot that might be getting too tall but is still a good, productive stem, so I’m now thinking of using this shoot just to tip off.
This tipping off is a different approach, and rather than cutting the spent flower just at its base, I cut the entire top of the stem back to the single side shoot or to a pair of side shoots at the height I want it.
This cut not only helps to reduce the size of the bush but also encourages the side shoots that are now at the top to grow vigorously and produce flower buds for the following year.
Lilacs are a marvelous traditional shrub that many gardeners have fond memories of. My hope is that, rather than destroying the senior lilacs in your yard, you could rejuvenate them.
Back in the early 1900s, some of the lilacs at the Wolcott Lilac Garden were planted and still grow there because someone cared to preserve these beautiful plants for the future. You can do the same.
Hope you have a great stroll through your garden this week. If you see some challenges, let me know at ericlarson546@yahoo.com.