Why Does My Lilac Not Bloom

A. There are a number of potential causes for your lilac’s failure to blossom. Lack of sufficient sunlight is the main culprit. Lilacs (Syringa) should be planted in an area with at least six hours of direct, bright sunlight per day. They can withstand a wide range of moisture levels as long as they are grown in soil with good drainage.

If your lilac is clipped at the wrong time of year, it might not blossom for another reason. Lilacs bloom in the spring on the growth from the previous year, and soon after, they begin to form the buds for the following year. Within a few weeks of the plant blooming, pruning must be done simultaneously with the removal of the wasted flowers in order to prevent the removal of the buds for the following year. A late freeze can harm flower buds on types that bloom early.

Lilacs have a tendency to mature into overgrown, leggy shrubs with minimal foliage at the bottom. When this occurs, it might be required to prune them to within 12 inches of the ground in order to completely rejuvenate them. When the shrubs are dormant in late winter, this should be done. Lilacs benefit from this repair, although their blooming cycle will be hampered for at least one season. Lilacs can receive a rejuvenation pruning over a two-year period to stop the interruption of bloom cycles. Half of the shrub’s stems should be hard pruned the first year, and the remaining stems the following year.

Lilacs do not consume a lot of food. Excessive fertilization, particularly nitrogen fertilizer, can frequently promote luxuriant vegetative growth at the expense of flower development. A lilac’s failure to bloom could potentially be due to its proximity to turf that receives frequent fertilization.

How can a lilac bush be made to bloom?

Lack of sunlight could also be a factor in your lilac plant’s failure to blossom.

You can grow lilacs that don’t have blooms in a location that is either shadowed by other trees or something else. It won’t bloom, but it will live.

For the best blooming, a lilac bush needs at least 6 hours of direct sunlight per day. It can be relocated or the trees that shade it can be cut back.

Be patient because transplanting lilacs may cause a one-year delay in bloom. To ensure that sunlight penetrates the foliage, you may also need to thin the bush.

How are lilac branches made to bloom?

By breaking dormancy, warm, 110° Fahrenheit water aids in the beginning of the forcing process. A floral preservative that is dissolved in the water provides nutrients and aids with disease prevention. You can either add a commercial preservative to the water or mix a quart of warm water with 2 tablespoons lemon juice, 1 tablespoon sugar, and 1/2 teaspoon bleach. Only 3 inches of the solution should be in the vase during the initial forcing, then add the lilac stems. After 30 minutes, complete the vase’s filling. As they emerge from dormancy, lilacs require temperatures between 60 and 65 degrees.

How can a lilac bush be revitalized to produce more flowers?

An old, overgrown lilac was one of the few plants that endured my garden restoration. The fact that it obscured my neighbor’s garage and, more importantly, sported steel-blue double flowers, led me to rescue it. Although the blossoms on this shrub were both lovely and fragrant, it was difficult to appreciate them because there were so few of them. I decided to go with a rejuvenation pruning because I knew there was no reason to give up on this long-neglected plant because lilacs can handle severe pruning.

On stems that are no older than five or six years, the common French lilacs (Syringa vulgaris cvs.) yield the most and the largest flowers. The flowers get fewer, smaller, and farther away as the stems get older. A lilac, however, may reliably produce blossoms for decades with the right trimming. The method you choose will depend on how old your shrub is. Plants are maintained annually to keep them healthy. A more drastic trimming may be necessary for lilacs like mine that have seen better days.

Lilacs should be clipped annually to encourage healthy stem development and strong growth that improves flowering. Cutting sick, deformed, and unproductive stems to the ground constitutes annual pruning. I thin and cut back some stems as well to promote healthy, evenly spaced growth. To prevent them from growing too far away from the center of the plant, I also pruned a few of the new shoots that emerged from the roots. I left a few inches between each stem to prevent crowding. Since they produce the most, I maintain the pencil-thick shoots that extend all the way to the ends of the branches. Small, twitchy growth is unproductive and won’t blossom. This growth can indicate an excess of aged, unproductive stems or too much shadow. Remove stems as soon as possible after blossoming, or in late winter if you don’t mind losing a few blooms. Cut off stems and shoots at or just below the soil line.

Dwarf lilacs rarely need pruning

Both the “Palibin” Meyer lilac (Syringa meyeri “Palibin”) and the “Miss Kim” Manchurian lilac (Syringa pubescens ssp. patula “Miss Kim”) are twiggy-habiting, somewhat small lilacs. On these types, just deadheading is needed in terms of pruning. You can prune some of the older stems as the plants get older to make place for younger, more robust stems. In contrast to regular lilacs, these plants hardly ever spread out of control. They might never need to be entirely regenerated if you only undertake a tiny amount of trimming every few years.

After the blooms have faded, deadheading, another aspect of annual maintenance, should be carried out as soon as feasible. Just above the two new shoots that slant out from the stem that stopped with the old bloom, the base of the old flower cluster should be cut off. The new shoots will develop throughout the course of the summer, produce flower buds, and culminate in a cluster of flowers the following spring. While not as crucial as the annual thinning, eliminating the old blossoms enables the plant to focus more of its energy on developing robust branches and flower buds. In June, I deadhead and thin my plants as needed.

While performing this yearly maintenance, I occasionally come upon a young, robust shoot that may be getting too tall but is still a good, productive stem and is a candidate for tipping off. I cut the wasted flower’s entire top stem back to one or two side shoots at the desired height rather of just cutting it off at the base. The side shoots that are now near the top of the bush are encouraged to grow vigorously and develop flower buds for the following year by this cut, which also aids in shrinking the shrub.

My own old, overgrown lilacs need more severe pruning. I went outside in the early spring before growth got going to get a good look at the bush. I looked to see if the plant had been grafted before I began chopping. I immediately cut it down to the ground as it hadn’t (for a grafted plant, see the panel below). I recognized that this drastic trimming would result in the plant losing part of its aesthetic appeal for a few years because lilacs bloom on the growth from the previous season. However, I was also aware that the reward—more blossoms and a stronger plant—would be worthwhile.

It’s crucial to nourish the plant after rejuvenation pruning with compost, composted manure, or a balanced chemical fertilizer and to make sure the soil pH is close to neutral, which lilacs appreciate. In the upcoming years, these supplements and some high-quality mulch will help to encourage vigorous new growth and enhanced flowering.

Has your lilac been grafted?

If your lilac has been grafted, check it out before you start making cuts to the stems. Grafting is a method of plant multiplication in which the scion, or branch, of one species is joined to the rootstock, or stem, of another species. This is typically done to enhance a plant’s look or traits. A graft union, where the cultivar’s scion wood joins the rootstock several inches above ground level, should be obvious. An apparent change in the bark from the rootstock to the scion’s bark, as well as a little swelling at the graft union, are things to watch for. If your plant has been grafted, all of your cuttings must be made above the graft union, and you must prevent shoots from the rootstock from developing into new flowering stems. Flowers of the desired shape or color will not be produced by shoots that emerge from the rootstock.

Does Epsom salt benefit lilac plants?

In zones 4–7 with cold summer weather, lilacs thrive. They are not advised for hot, muggy regions like zones 8 or 9. On the leaf, a powdery mildew may develop in hot, humid conditions. Lilac plants don’t require a lot of organic feeding or fertilization. To encourage flowering, we advise applying a fertilizer that is high in phosphorus and low in nitrogen. Poor blooms can be the result of too much nitrogen in the soil. You can add cow manure to the soil to encourage flowering if the fertility of the soil is low. Because it increases the alkalinity of the soil, bone meal is also an excellent fertilizer for lilac plants. The lilac can easily consume bone meal, a natural plant food. Use Epsom salt on your lilac plant once a month to encourage bushier growth and more blossoms (2 tablespoons of Epsom salt per gallon of water).

Can you grow lilacs with Miracle Grow?

3. Take the plant out of its pot and place it in the hole. Make sure the top of the root ball is about an inch or more above the soil surface.

4. Apply the soil mixture all the way around the root ball, pressing it down firmly.

5. Take a long drink.

6. Mulch the area you just planted to a depth of 2 inches, being careful not to pile mulch up against the base of the plant. This will help keep the soil moist and prevent weeds from sprouting by denying them access to sunlight.

How to Water Lilacs

After planting, monitor your plants frequently, and water them once or twice a week, or anytime the top inch of soil becomes dry. While watering, count to 10 to make sure you’re providing each lilac plant with enough moisture. (If the plant becomes too dry, the leaves will start to droop.) You can reduce watering to every other week once plants have been planted and have had a few months to establish themselves. Lilacs won’t require additional water during the second growing season or later unless there hasn’t been rain in your location for a month or more.

How to Feed Lilacs

Lilacs should be fed Miracle-Gro Shake ‘n Feed Flowering Trees & Shrubs Plant Food after they have bloomed in the spring to encourage the development of robust roots. This plant food is jam-packed with nutrients for your plants, including kelp, earthworm castings, feather meal, and bone meal. These ingredients nourish soil bacteria, which in turn break down organic matter into nutrients for your plants.

How to Help Prevent Disease Problems with Lilacs

Powdery mildew is the main problem with lilacs, especially common lilacs. What’s the best approach to prevent this? Purchase and plant lilac cultivars that resist powdery mildew (check the plant tag or online description). Lilacs benefit from being planted in areas with good airflow. This fungus disease won’t respond to spraying, and it will finally go away on its own.

How to Deadhead Lilacs

Be sure to deadhead young lilacs as they start to bloom (this could take a few years!). Deadheading involves clipping off faded flowers at the base as soon as they start to droop and fade. In response, the plant will use more energy developing new flower buds for the upcoming spring.

How to Prune Lilacs

Although the newer, smaller lilac kinds require less trimming than the enormous conventional lilacs, all lilacs will grow more effectively and bear more flowers with regular pruning. Here are a few possibilities:

  • Cut an older lilac shrub to 8 inches above the ground in late winter (March or April), then let it grow out if it isn’t flowering despite receiving plenty of sunlight. The following March, choose 8 to 10 of the best-looking stems, and reduce them by half. Trim the remainder to the ground. The following year, new blossoms should appear.
  • Selectively prune 1/3 of the branches all the way back to the ground each year to revive shrubs that aren’t flowering well instead of chopping the shrub all the way down.
  • Cut back branches to reduce size as soon as the shrub’s flowering has finished.

Which month should lilac bushes be pruned?

All lilacs should generally be clipped right away in the spring after they have finished blooming. Lilacs set their flower buds for the following year immediately after the current year’s flowers have faded, therefore trimming later in the summer or fall will result in the removal of most or all of the blossoms for the following year. The larger common lilacs as well as the shorter or more “shrub like” cultivars are all subject to this timing guideline. While the “when” of lilac trimming is rather simple, the “how” is a little more difficult. For the time being, we’ll refer to lilac pruning as either maintenance pruning or rejuvenation pruning to keep things simple.

How can I fix my lilac bush?

Examine the branches for damage like as exit holes and sawdust, sap, and frass, which are indicators of insect infestation. Damage from damaged branches could be stopped by pruning them off. Next spring, as the lilacs begin to bloom, keep an eye out for the adults and place pheromone-activated traps (see Lilac borer).

Can I prune my lilac shrub all the way back?

Older lilacs only bloom on the tallest branches and can have stems as thick as small trees. Fortunately, rejuvenation pruning can bring back a lilac that has been dead for around three years. There are two options available to you.

Using the “third” method is a less harsh way to pull an out-of-control lilac back into shape. For three years in a row, completely remove a third of the oldest branches from the tree. The thickest stems should be removed first. Pruning overgrown lilacs is simplest in the early spring before the branches start to leaf out, even if you’ll lose some blossoms for the current season. Your overgrown lilac should consist primarily of new shoots after three years of consistent pruning. After the plant starts to bloom all over, you may start doing routine maintenance pruning.

You can take the dramatic action of pruning back the entire plant to 6 to 8 inches above the ground in the early spring if you don’t like the way your old lilac looks or you just want a quicker solution. To encourage new development, fertilize the plant with compost or a balanced fertilizer. Throughout the growing season, new shoots will appear; allow them to continue to develop over the summer. The following spring, start cutting the spindly growth while keeping the healthiest shoots and keeping an eye on the plant’s shape. By pruning the remaining shoots to just above a bud, you can promote branching. After this, continue with routine maintenance pruning.