Have you wondered why your Lilac bush is not blooming? There can be several reasons and I list them here and how you can fix them. I get asked all the time why someone’s lilacs are failing to bloom so here you go. A full list of reasons for non-blooming Lilacs.
My lilac is not blooming. I get asked frequently on my Lilac Growing post “why aren’t my lilacs flowering or blooming?” So I decided it was time to give it full attention.
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For more on growing lilacs see links at the end of this post.
There are several possibilities and I tried to list most of them.
Your lilac may not be blooming because a late freeze damaged the blooms.
1.We get late freezes often here in April and May. If the freeze is severe it damages the lilac buds enough that they fall off.
We either get no blooms that year or very few. The plant itself is fine but we must wait another year to enjoy a bounteous display of fragrant blooms.
If you know you get late freezes you can plant your lilacs closer to a building. If you have established plants and you find out you will get a late freeze you can cover the lilac with a blanket, garden cover cloth or sheets. Many times a late freeze will be only a night or two.
Improper Pruning of Lilac Bush
2. The buds were pruned off last year.
The new buds form shortly after the flowers die back so any hard pruning should be done as soon as the plant is done blooming. Here that is in June. (it may be different in your area)
If you prune after that then you need to be more judicious. For more on pruning Lilacs see this post, I go through why to prune as that determines how you prune.
Insufficient amount of light to bloom
3. Another reason your lilac is not blooming could be that the plant is not getting enough sunshine.
Lilacs lacking in blooms can be planted in an area that either shaded by other trees or something else. It will live but not bloom.
A lilac bush needs at least 6 hours of sun or more in order to bloom their very best. You can move it or prune back the trees shading it.
Be aware that moving it may cause it to not bloom for another entire year so be patient. Also, you might need to thin the bush to make sure sunlight is getting through the foliage.
4. It has not been pruned or maintained for over 5 years.
Lilac bushes bloom best on younger wood, 5 or 6 years old and, if your lilac is mostly wood older than that then the number of blooms will be reduced.
You will need to do a rejuvenation pruning on the bush. See the link above for how to prune you Lilacs.
Wrong Lilac Fertilizer
5. Is your lilac near your lawn that gets high nitrogen feed to green it up?
Lilac bushes that won’t bloom could be the result of too much nitrogen. Lilacs don’t typically require feeding, improper fertilizing can cause a lilac to take up too much nitrogen, which encourages the plant to green up but prevents the lilac bush from blooming.
If you have a lilac near a lawn and don’t want to move it try adding phosphorus to the soil around the lilac. Bone meal is a great way add phosphorous but be aware it also can attract critters. Rock phosphate is another and Bat Guano too.
But really if you just add a good compost as a mulch around the base of your Lilac you should do fine.
Your Lilac gets too much water
6. Lilacs don’t like wet feet.
Many of the best performing lilacs around me are in gardens of homes that are not lived in and they get no supplemental watering all summer.
We don’t get summer rains, so they survive on what they get in the winter months. If your lilac is failing to bloom check to see that it does not get too much water.
A lilac does not need more than an inch a week during hot, dry weather.
Is your container Lilac not blooming?
7. A lilac planted in a too small of a container will fail to bloom.
Pot it up into a larger container using a good potting soil (not one with added fertilizer) and give the roots some room and you should be rewarded with blooms the following Spring.
8. Around here I have not noted pests in the lilacs.
But in other areas Lilacs not blooming can be because of borers and or scale. If it is pests, normally the entire plant will look to be suffering.
Your non blooming lilac may need a good rejuvenating prune to eliminate the borers and scale. Scale can be also treated with Neem oil while the plant is dormant.
Be judicious with Neem oil, it is an organic solution but still is broad spectrum. Meaning it kills good bugs too.
An extremely warm winter can prevent Lilacs from blooming.
9. Cold winter weather helps to promote blooms. Think back, was your winter warmer than usual?
To bloom well Lilacs need a certain number of days of cold. There are some varieties now available that do well in warmer climes. I list them in this post.
A lilac not blooming may need a whipping
10. I know people think this is odd, but it does seem to work.
Take a broom stick, rubber hose or something similar (some feel a rolled-up newspaper is enough) and whip the trunk of the lilac in early spring. (since Lilacs set their buds the previous Summer you won’t see results until the next blooming season)
I was taught this by a nurseryman I found one day beating plants with a short piece of rubber hose at his nursery. This works not only on lilacs but on fruit trees as well.
The reasoning behind this is it shocks the plant into production.
I hasten to add there is no science to support this. (garden myth?) However, when plants have mechanical stress, this can cause them to produce ethylene gas which may affect the blooms.
So as a last resort to get your failing to bloom lilac to perform, give it a good beating and see what happens. If done right it does no harm to the plant or the environment, so why not.
And that my friends is some of the most common reasons a Lilac may not be blooming or won’t bloom.
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