Sweet-smelling heralds of spring, the sweet and heady panicles of the Lilac bush are one of our favorite early-blooming flowering ornamentals!
But a Lilac that doesn’t flower is heartbreaking!
There are several reasons a Lilac may not be blooming as it should, and most can easily be fixed for blooms next year. It’s all about paying attention and a bit of timing and planning. Here are some of the top reasons why your Syringa may be failing to bloom and how to fix it!
Reasons Lilacs May Not Bloom
Narrow down the reasons your Lilac shrubs may not be as grand in the spring by checking out these common gardener mistakes that may be the cause of your lack of those highly sought-after blooms!
#1 Pruning At The Wrong Time
One common mistake some new gardeners make is to prune their flowering shrubs at the wrong time of year. Lilacs bloom on old wood, also called last-year wood. This is growth that started last growing season and overwintered, and it’s this growth that will have this spring's flowers.
Getting ahead of yourself during the fall clean-up rush or during that brief warm spell in late winter or very early spring will result in you trimming your Lilac shrub prematurely - and whoops - there go all your blooms for this year!
Solution
Lilacs and other shrubs that bloom on last year's old wood growth should only be pruned immediately after they flower. Once those blooms fade, go ahead and give your shrub a good pruning, removing no more than one-third of the plant at a time to keep it neat and tidy. For reblooming Lilacs, these too should be pruned by deadheading and slightly shorten up any branches that need be, and this should be done right after the first round of flowers finishes. This will encourage a fresh flush of new growth and more flowers in summer or fall. Renewal pruning is also suggested to rejuvenate overgrown Lilacs by selectively removing the largest, fattest stems to the ground leaving the younger stems in place.
#2 Not Enough Sun
Lilacs and other flowering and fruiting plants need the power of the sun to draw out the most blooms each year! Anything less than 6 hours of direct sunlight a day will result in far fewer blooms. While there are a few varieties of Lilac that bloom in partial shade, all Lilacs appreciate the all-day sun if you can give it, favoring the dew-drying powers of the morning sun!
Solution
Have a Lilac that got shaded out by a tree or other shrub that outgrew it, or you planted it in the wrong location? Try pruning back the other plant that is shading your Lilac so it can receive that much-needed sunlight. Otherwise, if it is young enough, carefully dig it up while it is dormant in the spring or fall, and relocate it to a sunnier location.
#3 Wrong Environment
As a transplant myself, I know the heartache of moving to a new area of the country and finding out all my favorite plants won’t grow in my new yard! For northern gardeners that have become snowbirds or moved to warmer climates, we’re sorry but you can’t bring your Lilac with you!
These flowering shrubs just can’t bloom in USDA growing zones 7 and up, with the exception of a few that can still bloom decently in zone 8. Lilacs can’t bloom in hot climates because of the lack of chill hours available. Chill hours are the number of consistent hours below a certain temperature during the winter months which trigger certain plant hormones to activate, and in this case - the hormones that initiate flowering. Not enough cold weather during the winter = no flowers.
Solution
Unfortunately, there isn’t a solution for this but there are tons of fragrant and similar plants that those in hot climates can offer! These include Butterfly bushes, Fragrant Tea Olives, California Lilacs, Chaste Trees, Pieris Andromeda shrubs, and Daphne bushes, or try some of the new shrubby GreatMyrtles that offer incredible color, summer into fall.
#4 Too Much Fertilizer
Many of us gardeners tend to give our plants a bit too much ‘love’ in the form of either water or too much fertilizer. Other gardeners feel that an application of fertilizer is a cure-all for what ails you, but unfortunately, it often does more harm than good!
Especially high-nitrogen fertilizers like those for your lawn can be detrimental to your Lilac's blooms! Nitrogen-rich formulas are great for turfgrass which is all about the greenery, and it does the same on flowering shrubs and plants - all greenery and no blooms. You’ll enjoy tons of growth but no flowers because who has time for blooms when you’re on a roll?
If you’ve been laying the fertilizer on thick, it can, unfortunately, take years to leach out all the excess nitrogen and get blooms returning to your flowering bushes. Overfertilized flowering shrubs may be burned from the excess salts in the soil or have the same symptoms as leaf scorch.
Solution
Stop fertilizing entirely in the area from the trunk to a few feet outside the ‘dripline’ of your shrub. Water well and apply a good layer of arborist mulch and lots of fertilizer-hungry leafy annuals and perennials to help leech out that excess nitrogen. You may consider having a soil test done to see exactly what your soil is needing and what your soil has in excess, your local County Extension Office can assist with this. Otherwise, it will take time to get that excess fertilizer to wear out of the soil.
If you have a Lilac or other flowering shrub now, choose only organic and/or a quality slow-release fertilizer geared for flowering/blooming plants and add a buffer zone of mulch or facer plants around your Lilac, extending out past the ends of the branches to keep lawn fertilizers away from their roots.
#5 It’s Time For An Overhaul
Old growth can be far less vigorous than new growth as many of our backs and knees can attest to! So if you have an established shrub that’s bloomed beautifully until now, it is most likely time for a renewal pruning.
Solution
By removing a third of the oldest, fattest, and woodiest stems right out at the base of the shrub above the soil line, you not only open up the interior of the Lilac to sun and air circulation but also stimulate fresh vigorous new growth to take its place.
For shrubs 3-5 years of age, removing a few of the oldest stems every few years will keep your shrub looking like a spring chicken, but for older shrubs, it should be done yearly to remove that old growth until it's all 3-5 years old growth once again.
Happy Lilacs = Happy Gardeners!
Avoiding these common mistakes with your Lilac bushes means armloads of flowers for your and your pollinator's enjoyment each spring! Keep your Lilac shrub looking its best for years to come with a bit of mindful care.
Need more information on caring for your Lilac bushes? Check out the Nature Hills Garden Blog or contact our knowledgeable customer service staff for more info! Then check out all the fantastic new varieties of Lilacs hitting the market on our website today!
Happy Planting!
