Reasons Why A Lilac Bush Is Not Blooming And How To Fix Them

lilac
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By Kathleen Mierzejewski & Heather Rhoades

Lilacs are very fragrant and having one or two in your yard in the spring and summer can make your surroundings smell fresh throughout the season. But what happens when a lilac bush never flowers? Having lilac bushes that won’t bloom is a common problem for gardeners. If you are wondering why is my lilac not blooming, keep reading to learn more about what you can do to make your lilac produce those fragrant flowers.

Why is My Lilac Not Blooming?

If you have a lilac bush that doesn’t seem to produce flowers the way you’d like, you are probably asking yourself, “Why won’t my lilac bush bloom?” There are many different reasons for there to be a lack of lilac flowering. Here are a few reasons why a lilac may not be blooming:

Late freeze – Sometimes a late freeze can knock the flowers right off the bush by damaging the buds. If your lilac bush is not blooming, you might want to think back about whether or not there was a late freeze. If this is why your lilac bush is not blooming, your bush is fine. Next year, you should have a ton of blooms.

Insufficient light – Another reason for your lilac blooming season to be lacking some flowers could be that the plant is not getting enough sunshine, which is what helps the plant produce flowers in the first place. Oftentimes, lilac bushes that won’t bloom are planted in a location where they get enough sun to live, but not enough sun to bloom. A lilac bush needs at least 5 hours of sun, and preferably a full day of sun, in order to bloom their very best. If you suspect that your lilac is not getting enough light, you will need to move it to a sunnier location in your yard.

Additionally, you might need to thin the area around the bush to make sure sunlight is getting through other foliage. Remove the oldest and thickest branches at the base of the bush to allow sunlight to penetrate throughout the bush.

Improper pruning – The next reason that makes a lilac bush not flower is improper pruning. Lilacs do not need to be pruned, but if you prune it back hard in order to rejuvenate the bush, it will take several years to recover and may not bloom during that time. Even lighter pruning, simply to shape the bush, can affect how well a lilac blooms. Pruning lilacs in late summer will cut away the wood that would have been the blooming wood for next year.

Age – Yet another reason for a lilac not blooming, or not blooming well, is that it is too old. Lilac bushes bloom best on younger wood and, if your lilac is mostly old wood, the number of blooms will be reduced. You will need to do a rejuvenation pruning on the tree, which will affect the blooming further for 2-3 years, but after that the lilac bush will return to full blooming.

Pests/Disease – Pests or disease can also affect how well a lilac blooms. If your lilac is not flowering well, check the plant for these. Problematic pests include scale insects and borers. You can see scale insects pretty easily on the leaves of the bush. If you see them, you will need to treat your bush so that it will do well the next lilac blooming season. If you see borer damage, you can alleviate this by doing your renewal pruning. This way new growth will come back without the damage from the borers and your lilac flowering will resume in the next season or two.

Fertilizer – Your soil may be at fault too. Lilac bushes that won’t bloom could be the result of too much nitrogen. Because of this, you should not fertilize your lilacs. They do not need much in the way of nutrients, and fertilizing can cause a lilac to take up too much nitrogen, which keeps the lilac bush from blooming. Also, lilac bushes planted near lawns may be taking up fertilizer used on the lawn. To correct this, you can add phosphorus (which is responsible for flowering in plants) to the soil around the lilac. Adding bone meal is a great way to fix soil that is lacking phosphorus. A soil test will confirm whether or not this is the cause for a lack of lilac flowering.

Root restriction – Another reason that a lilac bush does not bloom is due to having a restricted root system. A restricted root system prevents the lilac bush from taking up enough phosphorus in order to bloom. Restricted root systems can be caused by overly wet ground, container grown plants in too small a container, and inadvertent root pruning. Typically, a lilac bush with a restricted root system will also grow poorly.

So as you can see, there are a lot of reasons for your lilac to stop blooming. All of these reasons, however, can be fixed pretty easily. Just study the tree and figure out the reason for no flowers, and you should be able to fix the issue in no time.

This article was last updated on

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