We love to have fragrant lilacs in our garden, so when they don't bloom it is very disappointing. This is a guide about what to do about a lilac not blooming.
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As far as a shrubs go, lilacs are a dream come true for the gardener. Once established, these landscaping beauties will throw out heavenly-scented, long-lasting blooms for years and years-and all with very little care and maintenance on our part. Why is it then, after weeks and weeks of anticipation and doing everything right, your lilacs always fail to bloom? Here are the eight most common reasons.
Reason #1: It's Not Getting Enough Sun
The fact that lilacs prefer being located on a site with full sun is an understatement. To thrive and flower, lilacs need a MINIMUM of 6 hours of sunlight every day. If your lilac bush is not blooming, check to see if your site is too shady.
Reason #2: It's Too Young
A lilac will not bloom before its time, and most varieties of lilacs won't bloom until they reach at least 3 to 6 years of age. Years 1-3 are spent growing and developing. Only then, and only when they are good and ready, will they produce their first blooms. When they finally do bloom, the first few years can be less than spectacular. Don't worry, be patient. It's worth the wait. Hint: Most lilacs purchased in containers have passed their first birthday and started to develop a good root system. They will generally flower sooner than bare-root shrubs.
Reason #3: It's Over Fed
Imagine stuffing yourself full of food and then trying to perform something that requires you to expend lots of energy (think Thanksgiving). This is how it is for lilacs getting too much nitrogen. The primary nutrients in fertilizers are Nitrogen, Phosphorus and Potassium (on the fertilizer package, they are listed in this order, N-P-K). Nitrogen promotes growth above ground. Phosphorus promotes growth below the ground (roots) and is most responsible for flowering. (Potassium helps with overall growth.) Using a fertilizer high in nitrogen will encourage your lilacs to produce an abundance of green leaves, while at the same time, prevent it from flowering. Fertilizing lilacs is not mandatory, and if your soil is nutrient-rich, your lilacs won't need feeding more than once per year in the early spring (if at all). When you fertilize, use a fertilizer with twice the ratio of phosphorus to nitrogen in order to promote flowering. Remember, grass craves nitrogen, so if you're fertilizing your lawn your lilacs may be getting over fed.
Reason #4: It's In Shock
If you've recently purchased a lilac for transplanting, it may still be adjusting to its new environment. Even if it was blooming when you bought it, you shouldn't expect it to bloom for the next year or two following transplanting. Lilacs need a fairly long period to settle in You may need to wait as much as 3 years before it fully recovers.
Reason #5: It's Dry
Lilacs don't like their feet constantly wet, but summer droughts can take a toll on the next year's flower buds. Keep your lilac on a regular watering schedule and adjust it for heavy rain or extended periods of drought.
Reason #6: You're Improperly Pruning
If you wait too long to prune (after midsummer) you're going to be cutting off next year's flower buds. Pruning should be done immediately after flowers die off, because next year's buds form shortly thereafter. If your lilac bush has become overgrown, cut back only the oldest 1/3 of the shrub each year over a period of 3 years.
Reason #7 : Your Soil's Imbalanced
Lilacs prefer a soil pH from 6 to 7 (a little on the alkaline side). If your soil is too acidic, or missing certain nutrients, your lilacs won't bloom. And testing your soil is the only way to know. Inexpensive test kits are available at more garden centers, or for the most accurate test, contact your county extension agency for labs in your area. If the results indicate your soil is too acidic, the International Lilac Society suggests spreading fireplace ash around the drip line of the bush for bigger and better blooms.
Reason #8: You're Growing the Wrong Variety
If you've purchased you lilacs from a reputable local nursery, this probably isn't your problem. Still, large discount garden centers sometimes stock zone inappropriate plants and shrubs. Most common lilacs (Syringa vulgaris) need a cold winter to allow it to set buds. If you live in an area of mild winters, a Meyer lilac (Syringa meyeri) may be a better choice for your garden.
If none of these reasons can be applied to your situation, consider giving your bush a light root pruning in early summer. Jam a sharp spade into the ground on two sides of the plant about 12 inches out from the trunk. And maybe next year will be the year!
By Ellen Brown
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Here are questions related to Lilac Not Blooming.
My lilac bush is 3 years old and produced 1 lilac bloom. What do I need to do so it will produce more lilacs next spring?
I would suggest giving it some fertilizer & checking with a person in a nursery or the plant people at the Home Depot or other nursery for the right kind & how much to give it & when, & whether or not to cut it back to make it bush out, etc. I've never seen one with just 1 bloom, but it might need something else in the soil as well. I hope this helps. Good Luck. : )
I bought 3 lilac bushes about 3 ft high 3 yrs ago. They bloomed beautifully, but there have been no flowers since, just green leaves. I did cut hoping to fix the problem. What do I do to get flowers again?
You do not say what your USDA zone is, and that may matter. Lilacs will not bloom if they do not get cold enough each winter, regardless of whether they were blooming when purchased or not.
For the last two seasons my lilacs have budded out, but then the buds just turn brown and never open into flowers. They had bloomed fine, if sparsely, before.
Hardiness Zone: 4a
By Lisa from WI
Call your county's extension office; the people there are master gardeners; familiar with your soil, and climate etc; and they can readily and easily tell you what to do! These folks are a fantastic resource! especially for us gardeners! good luck!
I planted an old fashioned lilac 3 years ago and it is still only about 1/2 foot tall. It looks very healthy, but does not grow and no blooms. What can I do?
Hardiness Zone: 5a
By Ruthie from Sullivan, IL
Soil is not clay and it is not black. I believe it is good soil but I have never had the soil tested but other things grow in the soil so I would think it is good soil. I know there was an old barnyard in this area at one time. Lilac is planted in full sun. Is there some kind of fertilizer that I could put around the plant?
I got a lilac 2 years ago. It bloomed one bud last year, but I am getting nothing this year. It is very green and healthy though. Do I need to put acid on it to help it bud?
By Elaine K.
Hi, I bought a Little Miss Kim lilac from home improvement store and it didn't bloom the next couple of years. It began to bloom and has since. I think you will be fine. I heard lilacs are sensitive and just thought that is why mine didn't bloom at first. Hope it will soon, best wishes.
I have a lilac bush in front of my townhouse. It used to be covered in flowers. Five years ago my HOA chopped it to almost nothing while it was in bloom. Since then I am lucky to get one or two flower bunches. The bush is back to the height it was before they chopped it, but without the flowers. Any suggestions?
By Kathy P. from Aurora, CO
The buds on my lilac just begin to develop, then they turn black and cease to develop into blossoms.
Hardiness Zone: 6a
By Toni from north eastern OH
Most of the country has had an extremely long and harsh winter season this year. I had lilacs in Nevada before I came to Florida, and each spring we had another freeze just about the time the lilac buds were forming. Of course, the buds froze too, and turned black. All the leaves on any trees that had budded out also froze and turned black. If even your overnight temps dropped to near freezing, that will happen, and it also affects fruit trees the same way.
Pat T of Florida
Why does my lilac bush have a blue colored substance on the bark of the trunk, but not the branches? It doesn't produce any flowers that bloom.
By debter 
I took 2 shoots off of lilacs from my dad's (same zone). It has been 5 years and no blooms. Any idea why?
I purchased one white and one deep purple lilac tree. This is their third season and they were three feet tall on purchase. For some reason they are flowering alternate years and even then only two blooms. What am I doing wrong, is it their age? The ones my mother had when we grew up flowered every year with a plethora of flowers. My soil is sandy and well drained they are in a sunny position. I have fertilized them with bone meal and manure.