“You are the smell of all Summers,
The love of wives and children,
The recollection of gardens of little children.”
— Pulitzer Prize winning American poet Amy Lowell
Amy Lowell’s love song to lilacs appeals to our sentimental side. But who isn’t sentimental about lilacs? Do they not melt our hearts and fill our memories with April’s first bloom and wafting sweet aroma? Don’t they make you think about lemonade and freshly baked cookies on grandma’s porch? For me, lilacs were a constant on my childishly constructed May Altar where my friends and I would light candles and practice devotions.
I was feeling that sentimentality when I found two lilac bushes in the garden of the home I purchased several years ago. Unfortunately, this year I am not happy and certainly not feeling sentimental about the few scraggly blooms one of the bushes has managed to produce. Follow me on my investigative journey. I am confident we will find a way to restore my bushes to their former magnificence.
The first thing I wanted to rule out was disease. I inspected the bushes for leaf damage. The dead leaves were confined to broken branches and probably victims of high wind. Leaf curl was minimal and might be attributed to late frosts. I found no evidence of insects although often when leaf damage is observed the insect is already gone. Had I found leaf miners I would have used Bayer Advanced Tree and , I am fairly convinced that the lilacs are not diseased. So far, so good.
Research revealed several things that can prevent lilac bushes from flowering. Lilacs need full sunlight and relatively dry soil. They do not like to be planted too deep. Too much nitrogen in the soil will make them put energy into growth rather than reproduction or flowering. Rock mulch, particularly with landscape fabric, creates an anaerobic condition in the root zone and discourages flowering. None of these apply to my lilac bush so I continue the research.
I learned that lilac trees form their buds for the following year in early summer so the best time to prune is right after blooms have wilted and fallen off. This could not be the reason for their bloom failure since I have never pruned them. However, further reading revealed that lilac shrubs left to grow and spread without pruning can reach heights over 20 feet. According to OSU Extension, the lower branches will likely be bare and the blooms will be out of sight and reach. Bingo! This is exactly my problem.
Now I know I must focus on the proper method of pruning. Even though lilacs bloom on previous season’s wood, without pruning we end up with a woody, unattractive plant that doesn’t produce a nice spring bloom show. This is my tree! Ideally, a lilac bush needs a mix of young new shoots and older stems. The newer stems won’t bloom for several years, but to keep the lilac bush blooming, young shoots are essential.
Large old branches need to be systematically removed. A rule of thumb is to remove a branch all the way to the ground when it is more than two inches in diameter. Regular annual pruning will maintain lilac bushes at an ideal height of around eight feet.
In order to keep your lilac bush developing new stems while the older stems are blooming remove about one third of the branches every year. The bush may be shaped as you are pruning. For more information, visit tinyurl.com/83bze5b.
If you would like to take a cutting from your grandmother’s bush you should know that lilacs are not easily propagated so timing is critical. Softwood cuttings before the leaves mature work best. Place these 8 to 10 inch cuttings in a sand or vermiculite medium with a root hormone. Be patient as lilacs grow slowly — only a foot to a foot and a half per year. If you are less patient consider moving the entire bush (with grandma’s permission, of course!). Carefully dig up a 36-inch rootball in early spring when the plant is dormant. The next best time is in the fall after the leaves have dropped.
Thanks for accompanying me on this stroll down memory lane. Wish me luck as I embark on my pruning adventure. I hope to one day soon see (and smell) my lilacs restored to their former beauty.
Michele Pearson is an OSU Extension Master Gardener volunteer.