Lilacs should be trained as trees from the beginning for optimal results. When young plants are quiescent, remove all lower branches and all other stems that are emerging from the soil, leaving only the whip. Between shin and knee height, cutting the whip low fosters the growth of several upright branches.
As the tree matures, a robust lower trunk with numerous strong leaders forms. An appealing tree with an open, rounded shape is produced by removing leaders to encourage them to rebranch and keeping sprouts and lower growth thoroughly removed. A topiary standard tree is produced by raising the whip’s termination point and maintaining a compact top growth.
When is a lilac shrub able to be shaped?
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 should a lilac tree be shaped?
Cutting off the tops of stems that have grown out of control is frequently insufficient when pruning lilacs. It is typically preferable to remove the entire stem. The best way to trim lilacs is with clippers. To avoid spreading and promote later blooms, remove spent blossoms right down to the stems. Three-quarters of the branches should be pruned. Remove any shoots that are emerging from the main trunk and are growing close to the ground. Lilacs within the inner branches may need to be trimmed in order to increase air flow or let more light through.
However, it may be essential to prune the entire bush or tree to approximately 6 or 8 inches (15-20 cm) above the ground if lilac shrubs are already too big or starting to look unpleasant. Remember that it takes around three years for flowers to grow after the entire bush has been removed, so you might have to wait.
Can you prune lilacs to keep them small?
Keep in mind that there are new dwarf types of lilacs available, such as the repeat blooming “Boomerang,” that tend to stay much shorter in height and can easily be kept shorter than 6 feet tall with yearly pruning.
How tall should lilacs be allowed to grow?
Pruning lilac bushes and shrubs on a regular basis has several advantages. A lilac can be kept at a specific size by cutting back, but well done pruning can also promote additional bloom growth. On younger, slightly weaker branches, lilacs bloom more profusely. Old, heavy branches will finally cease to blossom altogether.
The ideal time to deadhead and prune a lilac bush or tree is immediately following the spring flowering period, or, as suggested by Gardening Know How, when it reaches a height of between 6 and 8 feet. By pruning the plant this early, it will have the entire summer and fall to grow back, which should ensure a plenty of blossoms the next spring. By removing the old blossoms once they have faded, you can deadhead the blooms. The plant can then concentrate its energy on developing new shoots. Never remove more than a third of a shrub’s total growth in a single pruning; this will leave enough of the plant for a healthy regeneration after a heavy clip.
According to Swansons Nursery, you should first remove any sick or dead vegetation. If required, prune right down to the root. Branches with a diameter of more over 2 inches should be cut back as they are older and won’t bear as many flowers. After that, prune back any growth that has grown too large for the lilac bush. The best place to prune is where the branch splits, but make sure the entire pruning operation prunes branches of various ages and thicknesses.
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.
Do lilacs need to be clipped annually?
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.
Can you trim back lilacs to the ground?
The lilac tree will resemble nothing more than a twig in the garden by the end of September. It shouldn’t be reduced to the ground, though. Despite the fact that lilac trees are known for their resilience, it will likely take several years before you see blossoms again because you cut off all the blossoming growth.
If your lilac tree is more mature and unruly, it may require more aggressive pruning and some chopping back; just make sure that it doesn’t take up more than a third of the tree.
What distinguishes a lilac tree from a lilac bush?
Lilac bushes (also known as shrubs) are characterized by their numerous woody stems that emerge from the plant’s base. In contrast, the trunk of the majority of lilac trees is the only woody stem. However, your neighborhood garden center might also sell shrub lilacs that have been grafted onto a single stem to give them the appearance of miniature trees.
The choice between a lilac tree and a lilac bush is typically determined by the amount of space available. Lilac bushes come in a range of sizes and can be placed in more compact areas of a garden. A lilac tree requires space to reach heights of 20 feet and widths of 15 feet. Both require sunlight to bloom well.
Zones:
The majority of lilac types can withstand cold temperatures in zones 3 to 8, although others, like Scentara Double Blue, can (S. hyacinthiflora). There are some cultivars that don’t require a winter chill, like as “Lavender Lady” (S. vulgaris), which is heat tolerant to zone 9. The majority of others do need a wintertime period of cold and dormancy.
Height/Spread:
The common lilac, Syringa vulgaris, reaches heights of 12 to 15 feet and widths of 10 to 12 feet. The majority of dwarf types are smaller and reach maturity at 4 to 6 feet tall and 3 to 7 feet broad. Syringa reticulata, often known as the Japanese tree lilac, grows up to 30 feet tall.
Bloom Time:
The majority bloom in late May, however there are new re-blooming kinds, such the Bloomerang series, as well as early spring, mid-spring, and late-season blooming variants.
Color:
The common lilac (Syringa vulgaris) has gray to gray-brown bark, purple blooms, and dark gray-green to blue-green foliage (with no fall color change). But there are actually seven recognized hues for lilac flowers: white, violet, blue, lavender, pink, magenta, and purple, with several variations of each hue.
Other:
True lilacs, such as the California, mountain, and wild lilacs, are truly members of the genus Ceanothus. Butterfly bushes are frequently referred to as summer lilacs, especially sterile and non-invasive varieties.