Every year, we receive calls from customers who are disappointed that their lilacs only sparingly or never blossomed, despite the fact that there were lovely lilacs blossoming all over the county, including on vacant lots and yards that appear to have never been maintained. The following is a list of the most frequent causes of lilac failure to bloom:
Shadow: When lilacs don’t bloom effectively, excessive shade is most likely to blame. Full daylight, or at least a half-day of sunlight, is ideal for lilac blooming. Less will result in fewer flowers emerging. Lilacs seldom ever bloom at all when they are in an area that receives shade all day. As the adjacent shade trees get higher and fuller over time, the shade can occasionally creep up on you. In many circumstances, the lilacs may have been first planted in an unfavorable spot.
Pruning: Lilacs may take a number of years to start blooming again if you severely prune them. They should ultimately bloom, but it might take three to four years, or even longer. You might not see many blossoms the following year if you merely lightly prune and wait until mid- to late-summer to do it. This is due to the fact that shortly after the plant finishes blooming, the flower buds for the following year are set. Therefore, if you do decide to prune, make sure to do it as soon as the spring flowers start to fade. You might at the very least want to get rid of the ugly brown flower/seed clusters.
Lilacs don’t consume a lot of nutrients, therefore they don’t require fertilizer to blossom. People frequently feed young plants multiple times each spring and summer in an effort to aid in their establishment. Additionally, there is typically some fertilized grass nearby. The lilac makes a lot of green, vegetative growth as a result of the excess of nutrients, notably nitrogen, which may interfere with the creation of flower buds. Stop fertilizing if this seems to be the case, provided the plant is receiving enough sunlight and hasn’t been cut excessively or at the wrong time. It should eventually start to flourish well.
Moisture: Lilacs thrive in soil that drains properly. While a lack of flowers isn’t directly related to a damp, poorly drained soil, it is related to plants that have root rots or don’t do well in general. If at all feasible, move a young lilac from a low-lying, wet spot to a more suitable one.
The general public is invited to visit the enormous lilac collection in the Lyle Littlefield Garden on the University of Maine’s Orono campus at any time of the year. Larks begin to bloom in early June. Rhododendron, magnolia, and crabapple cultivars are also included in the Littlefield garden.
Lyle E. Littlefield, a professor of horticulture and extension specialist at the time, founded it in the early 1960s. The Littlefield Garden has acquired a collection of more than 2,500 woody and herbaceous plants over the past forty years. Plan to visit the Littlefield Garden if you happen to be in the Orono region. On the Orono campus, it is next to the Hilltop dormitory complex.
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.
Do lilacs require pruning?
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.
How late can lilacs be pruned?
Between April and June is the best time to prune lilac bushes, but only after they have stopped blooming. Although it may seem strange, lilac bushes bloom on the growth from the previous year, therefore by pruning sooner rather than later, you won’t damage the blossoms in the following year. The same holds true for lilac tree pruning techniques.
Can lilacs be severely pruned?
Cut down overgrown deciduous shrubs to within 4 to 6 inches of the ground in March or early April as a second method of pruning. A significant number of shoots will sprout during the growth season as a result of this aggressive pruning. Select a few sturdy, healthy shoots to keep, then cut off the rest at ground level in the late winter of the next year. The retained shoots should be headed (trimmed) back to promote branching. This method of pruning can be used on large, overgrown lilacs, honeysuckles, dogwoods, spireas, barberries, blooming quince, and forsythias. Some plants, like lilacs, will not bloom for three to five years after this technique of pruning.
How are lilacs prepared for the winter?
When choosing a location for your lilac shrub, consider the winter climate. For this plant to thrive, it requires alkaline to neutral soil and at least 8 hours of direct sunlight per day. Do not place them up against a wall or structure with light colors. Winter burn may be caused by the reflection. Cover the plant’s base with 3 to 4 inches of mulch to help minimize winter heave (the exposing of roots caused by the freezing and thawing of the earth). If a severe freeze occurs in the late winter or early spring, you might need to cover your shrub to keep the new buds safe. You can use burlap, a blanket, or a plastic tent.
How are overgrown lilacs pruned?
Similar to the lilac, heavy pruning needs to be done over a number of years. Remove any dead, spindly, dying, or ill-looking wood first. At the base, remove roughly a third of the tallest, oldest branches. The remaining branches should then be cut back by at least a foot. Over the following two years, repeat the same action.
Azaleas and rhododendrons prefer somewhat acidic soils. The optimal time to fertilize in the spring is right after flowering. Though slightly more expensive than chemical fertilizers, organic fertilizers release their nutrients gradually and require less frequent application. After July 15, refrain from fertilizing to prevent the plant from going into full dormancy before winter. Use of lime or alkaline fertilizers should be avoided.
In the summer, rhododendrons and azaleas require a lot of water due to their shallow, fibrous root systems. Make careful to thoroughly hydrate them. You will require water all year long if they are planted beneath wide eave overhangs. Avoid going too deep when hoeing or raking around the plants. Mulches can be used to control weeds, maintain more consistent soil temperatures, and save moisture. Examples of such mulches include sawdust, bark dust, peat moss, straw, or other organic materials.
The garden is busy at the moment. These days, your vegetable garden can contain just about anything. Don’t put it off! Plant more lettuce, carrots, beets, potatoes, peas, cucumbers, squash, pumpkins, melons, dill, basil seedlings, and brassicas. Also plant more beans, tomato and pepper plants, and more lettuce.
Lilacs can be pruned in the winter.
Lilacs should be clipped no later than two weeks after they have finished blooming in the spring, if you’re wondering when to do it. Since lilac bushes start to form buds in the summer and those buds last through the winter in preparation for the next spring’s bloom, cutting at any other time of the year would be a mistake.
Even though you’ll be removing prospective flowers, you can prune in the late winter if you’d rather do it while the plant isn’t covered in foliage. To learn how to prune a lilac shrub, follow the instructions below, regardless of the cutting method you decide on.
Should lilacs be deadheaded?
The removal of spent flowers to encourage new blooming—deadheading—is a crucial part of lilac maintenance. Lilacs should be deadheaded as soon as the flowering is finished to allow the plants to grow robust, healthy buds that will flower vivaciously the following year. According to the University of Minnesota Extension, you can use a hand pruner, but larger plants could require a hedge trimmer. Only the dead blossom should be removed; the plant should still have two leaves.
According to the Chicago Botanic Garden, you should prune lilacs at the same time as you deadhead them since they set the blossoms for the following year quickly after flowering. By doing this, you can prevent damaging or removing the developing buds. Three to four years after planting, you should start pruning lilacs. It might be necessary to trim back overgrown lilacs to just a few inches above the ground. Winter is the ideal time to complete this. In this instance, it will take the shrub one or two growing seasons to start blooming once more.
Does new or old wood produce lilac blooms?
What specifically prevents these traditional plants from blooming? Instead of focusing on just one theory, consider a number of potential causes for this issue, including (in addition to illnesses and pests):
- Pruning when it’s not necessary
- The flower buds die in the cold
- placing your lilacs in the incorrect location
- The shrub in question either isn’t old enough to generate flower buds or is too old to do so.
You’ll see that while reasons one and three point to the gardener having done something incorrect, arguments two and four point to no one having done anything incorrect.
Why does it matter what time of day you prune? Shrubs called lilacs produce flowers on rotting wood. This indicates that the flower buds for the upcoming spring’s blooming season have already been formed on the growth from the previous year. When this growth is pruned, the flower buds and, consequently, the blooms they would have produced, are lost. Because of this, it is recommended that you clip lilac bushes as soon as they finish flowering (before they have set bud for next year).
Click Play to Learn How to Prune Lilacs
Despite being a relatively cold-hardy plant, the common lilac (Syringa vulgaris) can suffer harm if a hard frost or freeze occurs just as the flower buds are about to open. As a result, that year’s flowers are lost. You can’t really stop it, so simply accept the loss and look forward to the blossoming twice as much the next year.
Where you put your lilac shrub matters a lot, just like it does with most other plants. Lilacs require full sunlight and prefer well-drained soil. If you made a mistake when you first put your plants on either of these fronts, you can be paying for it today by your lilac not blooming. However, there is a simple solution to the issue: move your shrub to a more favorable location.
Regarding the fourth reason, be aware that although though these bushes have a long lifespan, they do tend to produce fewer flowers as time passes. Implementing a rejuvenation pruning on your lilacs will solve this issue (do not expect immediate results, though). Sometimes, though, the converse is true: your plant may be too young to bloom. Allow some time.