Common lilac (Syringa vulgaris) is anything but ordinary. The lavish spring blooms of wild species and noble varieties are legendary. With the right pruning care you can maintain and optimize shape, vitality and abundance of flowers. This tutorial explains in a practical way when and how to cut lilacs expertly. A comprehensible guide for raising a lilac tree explains step by step how it works.
When should you cut lilacs?
Cut the lilacs at the end of May at the earliest. Then its heyday is over. After planting, cut the lilac the following spring to ensure lush blooms and strong vitality. Lilacs must not be cut during the breeding season.
Many types of cutting – one goal: this is how lilacs remain shapely and blooming
Lilacs are characterized by lavish spring blooms and legendary longevity. The valuable flower wood remains vital for up to 20 years. If left uncut, the lilac bush and lilac tree lose their harmonious shape, older branches age and internal branches die. Ultimately, the neglected lilac becomes bare and presents itself in the outer area with unsightly branches that carry a few small flower spikes. You can counteract this process with pruning care at the right time. The following table summarizes all types of cuts with recommended dates:
| Cut style | Goal/Occasion | best date |
|---|---|---|
| Plant cuttings shrub | dense branching from the base | after planting or the following spring |
| Structural pruning shrub | cultivate a harmonious shrub shape | first to third year |
| Educational pruning tree | Treating a lilac tree with an even crown | February to early March |
| Cleaning | well-groomed appearance, prevent seed formation | at the end of the flowering period |
| Blending cut | Thin out dead wood and unfavorable shoots | February to early March |
| Rejuvenation cut | revitalizing aged lilacs | November to the end of February |
With the exception of removing wilted flowers, we recommend early spring as the best time for pruning care. The reason for this appointment recommendation is the growth behavior. Lilac lays the buds for next year during its current flowering period. A vigorous pruning after the flowering period destroys the majority of the freshly formed buds. The growth of leaves and shoots can no longer be expected in summer, not to mention next year's flowering period. If you cut in the spring before the flowering period, the buds will also fall victim to the scissors. However, at this time they are swollen and clearly visible or have already sprouted, which allows targeted incisions. Last but not least, the legislature has a literal say in the scheduling of far-reaching cutting measures, such as thinning and rejuvenation.
Background
Thinning out and rejuvenating lilacs is subject to a legal time limit
Lilac bush and lilac tree are a popular place for local birds and feathered summer visitors to nest in the densely leafy branches. To ensure that the breeding business remains undisturbed, the Federal Nature Conservation Act has strictly regulated cutting measures on hedges and trees. Thinning and rejuvenation is permitted from October 1st to February 28th, provided there are no overwintering wild animals in the woods. During the grace period from March 1st to September 30th, the law allows light care cuts, such as cleaning out withered inflorescences. Violations result in a fine of up to 50,000 euros.
Pruning prevents bare bush bases
The best time to plant bare-root, inexpensive lilacs is in autumn. For young shrubs in containers, the window for planting is open all year round, as long as it doesn't freeze. Regardless of when and how you plant lilacs in the ground, you can create strong branching at the base with the following planting cut:
- Bare root goods: cut off damaged roots, cut back all shoots by half
- Container goods: trim shoots by a third, remove weak, broken branches
- Result: Failure of the first flowering period, in return strong shoots at the base of the plant
Home gardeners thirsty for knowledge ask themselves why the reaction of the lilac bush to the planting cut can be reliably predicted. One of the three fundamental laws of growth allows for a reliable forecast. According to the Top Promotion Act, growth from top buds is significantly stronger than from buds below them. This applies equally to the plant per se and its individual shoots. If you cut off buds with a top position when planting, lower-lying buds take on this function. The sap pressure then increases and causes strong budding.
Building a well-formed lilac bush - this is how it works
The plant cut provides the floral initial spark. With pruning in the following two to three years, you can guide the growth of your lilac bush towards a harmonious shape. The figure below illustrates the pruning measures and the manual intervention on the rootstock. This is how the build-up cut works:
- Best time is February to early March
- Natural and refined lilacs: grow with 5 to 7 scaffold shoots
- Rootless shrub: select vital ground shoots, pull out excess ground shoots
- Refined shrub: Determine shoots above the grafting point for the framework, pull out all shoots below the grafting point
Please do not cut back scaffold shoots under any circumstances because they bear the buds for further growth and flowers. If a flowering period is coming to an end during the multi-year development phase, cut off any withered panicles. Place the scissors at a short distance from an outward-facing bud.
Noble lilacs and wild species benefit from a harmonious framework structure. Train the shrub with 5 to 7 ground shoots that will remain vital for many years. Tear off any excess ground shoots with a jerk.
Training a lilac tree – it’s that easy
A modified pruning approach is required when training a young plant to become a lilac tree. Completely trained standard trees from the hands of the master gardener cost 50 euros and more. Since magnificent noble lilacs, such as 'Souvenirs of Ludwig Späth', can be purchased as unrooted young plants, ambitious home gardeners carry out the training themselves. A young bush with a strong central shoot offers the perfect starting point. This is how it works:
- Tie the middle shoot to a stable support rod
- Remove competing shoots growing from the ground and all side shoots
- Guide the middle shoot as a future trunk on the support rod up to the desired height
- Cut off the tip of the trunk when it is 3 pairs of buds above the desired crown height
- Build a crown from four to five strong side branches
- Remove all other side branches and competing shoots
A lilac tree looks just as decorative when it is trained as a small tree with two to four trunks around a raised central trunk. This version is recommended if the gem is presented in the middle of a spacious park. In practice, the lilac standard has emerged as the ideal form of training for small gardens and in pots.
Tip
Don't cut your lilac just anywhere, but precisely just above a pair of buds facing outwards. With this cutting technique you show the growth of new shoots the right way. Place the scissors at a maximum distance of 5 millimeters from the opposite buds or leaves. Do not leave any longer stubs and do not cut into the leaf nodes. Your lilac will thank you for your careful pruning with he althy, vital shoots.
Clean up wilted flowers for a well-groomed appearance
Once construction and training have been completed, pruning care culminates in the annual cleaning out of withered flower spikes. Home gardeners primarily use this method to give wilted lilacs a well-groomed appearance. The extent to which the measure then invests more energy in bud formation is controversially discussed among experts. Since you run the risk of destroying buds that have already formed when cleaning out, please proceed with caution.
As the illustration below shows, cut just below a wilted flower spike. Choose a pair of buds facing outwards as the starting point for the scissors. Branches sprouting from it make your lilac appear more voluminous and do not cause any shadows to be cast inside.
At the end of the flowering period, cut off all withered flowers. Be careful: the buds for next year are already underneath the withered inflorescences. Place the scissors just under a spent panicle.
Pruning keeps the bush and treetop vital
On skillfully trained lilac bushes and lilac trees, pruning care for many years is limited to cleaning out withered inflorescences. Wherever the ornamental tree feels comfortable, it will provide you with vital flowering wood for up to 20 years. If there is still reason to complain about a lilac that is rotten or balding, a thinning cut will solve the problem. How to proceed professionally:
- The best time is in late winter to the end of February/beginning of March
- Lilac bush: thin out aged ground shoots to 5 cm short cones
- Lilac tree: free the crown from dead wood and unfavorably growing branches
As shown in the illustration below, cut off old scaffolding shoots from the unrooted lilac bush just above the ground. If it is a grafted lilac bush, cut above the grafting point. Choose promising, young ground shoots as replacements and remove all weak and unfavorable wood.
It is important to note that when thinning out the crown of the lilac tree, the cut is on the branch. Do you feel compelled to eliminate an old guiding instinct? Then position the saw so that the small bead between the branch and the trunk is not damaged. If you cannot see a branch ring, please avoid cutting into the trunk bark.
In early spring, remove dead and unfavorably growing shoots from your lilac bush. If you haven't already done so, cut off spent flower spikes. Use this example to thin out the crown of the lilac tree.
Excursus
It's better to pull out wild shoots
The most beautiful lilac varieties are grafted onto the rootstock of the wild species. The rootstock demonstrates its growth power through the vigorous sprouting of wild shoots. The shoots can usually be recognized by a different leaf shape and larger leaf spacing (internodes). With rapid growth, the shoots known as water shooters strive to overgrow the noble part and rob it of its nutrient supply. Stay on the trail of game shoots promptly throughout the year. If a shot of water catches your eye, tear it off with a courageous tug. The less residual tissue remains on the root, the lower the risk that a wild shoot will shoot up there again.
Rejuvenate the lilac bush properly – step-by-step instructions
If an old lilac bush is only remotely reminiscent of its legendary spring splendor, you can rejuvenate it. Radical pruning has the best chance of success in late winter, shortly before growth begins. By choosing a date, you also comply with the regulations of the Federal Nature Conservation Act, as the grace period begins on March 1st. How to revitalize an aging lilac bush:
- Cut off one to two thirds of senescent ground shoots on short cones near the ground
- Remaining scaffold shoots divert onto a lower, young side branch
- In the following late winter, build up strong, outward-facing ground shoots as a new framework
- Ideally tear off all remaining shoots from the rootstock and do not cut them off
Do old scaffold shoots have no young side branches to draw from? In this case, cut back all shoots in February to different cutting heights of 20 to 80 centimeters, as shown in the figure below. Then fertilize with mature compost and horn shavings to encourage growth. Give the revitalized lilac bush until next February until you start rebuilding with the 5 to 7 most promising ground shoots.
To rejuvenate an old lilac bush, shorten all shoots to 0 to 80 centimeters above the ground in late winter. Numerous young shoots then sprout. In the next late winter, select 5 to 7 of the most vital ground shoots and initiate the rebuilding process.
Rejuvenate an old lilac tree in stages - here's how to do it right
If a lilac tree remains uncut for many years, a densely branched crown with numerous, thick leading branches forms. Typical symptoms of an advanced life cycle are increasingly smaller leaves and flowers as well as progressive baldness of the crown from the inside out. The older and more majestic a lilac tree, the more carefully you should approach it. Spread the rejuvenation over at least three years. Don't just saw off thick, old branches in one go. How to do it right:
- The best time is during the leafless period between November and February
- Do not thin out more than one or two old crown branches each year
- First saw at a distance of 40 cm from the actual cut point to the middle of the branch
- Move the saw 10 to 20 cm to the right or left
- Sawing until the branch breaks through
- Saw off the remaining stump on a string
Crown branches that you do not remove on Astring will receive a derivation cut. Select a strong side shoot, where the old leading shoot and young wood fork, place the saw. After the cut, the previous side shoot acts as a new leading shoot. During the rejuvenation stages, fertilize the lilac tree with 3 liters of compost and 200 grams of horn shavings per square meter of tree disk. Rake in the fertilizer lightly and water again.
Background
Lilac tree controls wound healing on its own
By following these instructions and sawing off thick, old branches step by step and on a string, you will initiate the plant's internal wound healing. If larger cuts occur on trees, dividing tissue (cambium) is exposed, which is located just below the bark. The cambium then transforms into a bulge of initially undifferentiated cells, the so-called callus. The open wound is gradually covered by callus. This process aims to permanently seal off dying wood from he althy wood. Interventions on the part of the gardener by sealing a cut wound with tree wax significantly hinder the healing process.
Hard wood requires stable cutting tools – tips on scissors and saw
Lilac wood is classified as hard to very hard wood. Shoots, branches and trunks are therefore just as strong and resilient as the wood of elderberry or firethorn. Furthermore, lilac wood has a reputation for quickly splintering and tearing when fresh, undried, which increases the risk of disease and pest infestation. Conventional secateurs from low-cost suppliers are hardly up to the task. Instead, choose the cutting tool for your lilac based on the following criteria:
- Shoots up to 1.5 cm in diameter: one-handed scissors with bypass mechanism for smooth cuts
- Branches up to 3 cm in diameter: one-handed pruning shears with ratchet gear to increase power
- Branches up to 4 cm in diameter up to 3 meters high: two-handed pruning shears with telescopic arms
- Branches from 4.5 cm in diameter: manual or electric tree saw, optionally as a pole pruner up to 4 meters high
Scissors for pruning trees are usually available from specialist retailers with a bypass or anvil mechanism. Anvil pruners work with a sharp blade and a blunt counterpart, which reduces the amount of force required. The disadvantage is that the shoot can be squeezed between the blade and the anvil. Since lilac wood tends to splinter, we recommend bypass scissors. This works with two sharp blades that cut through the hard wood smoothly.
The 3 most common cutting mistakes
Misunderstandings in pruning care leave a flowerless or prematurely senescent lilac. Sometimes the gardener is overzealous when it comes to rejuvenation and struggles with the total failure of a plant that can naturally live more than 100 years. To protect you from such mishaps, the following table names the 3 most common cutting mistakes and provides tips for prevention.
| Cutting errors | malicious image | Prevention |
|---|---|---|
| strong pruning after the flowering period | Failure of the next flowering period, no or low shoot growth | just clean it out after flowering |
| never photographed | many dead branches, baldness from the inside, few flowers | thin out every 2 to 3 years in spring |
| put old lilacs on the stick in one go | Total loss of shrub or tree | rejuvenate aged lilacs in stages |
Lilac blossoms are in great demand as vase decorations. A common mistake when pruning a vase leaves gaps in the appearance of the shrub or crown. Please do not cut the tips of scaffolding shoots or crown branches for the vase. Side branches that are already in an unfavorable position are more suitable.
Tip
Don't you feel like dealing with an old or bare lilac tree? Then, as the flowering period progresses, cut one or two beautiful bouquets out of the crown or bush for the vase. You will receive a fragrant floral decoration for your home and effectively prevent premature aging.
Frequently asked questions
Is lilac poisonous?
Lilac does not use defensive strategies such as stinging hairs, thorns or razor-sharp leaf edges. In order to defend itself from its enemies, the ornamental tree relies on poisonous ingredients. A toxic glycoside called syringin is found in leaves, flowers, roots and bark. Furthermore, the lilac bush and lilac tree are filled with alkaloids and essential oils that are harmful to he alth. Consumption can cause nausea and vomiting. Skin contact causes allergic reactions in sensitive people. Fragrance allergy sufferers suffer from breathing difficulties when around lilacs.
Our wild and noble lilacs have grown well and have already bloomed once. Unfortunately, the bushes are only sparsely branched. Can pruning fix the problem?
Like all trees, wild lilacs and noble lilacs grow persistently in the direction of sunlight. The branching in the lower part of the bush is neglected. Next spring, cut back all shoots by a third or half. The cut causes sap to accumulate on the lower buds, which then sprout vigorously. The flower buds are lost for the next flowering period. The effect on branching at the base of the bush is of course permanent.
I read that a lilac bush forms extensive runners. How can I prevent paths or buildings from being damaged?
You will keep the growth of runners in check if you line the pit with a root barrier when planting. This is non-rotting, impenetrable tissue. It is important to note that the root barrier extends at least 50 centimeters deep, is laid without gaps and protrudes 5 to 10 centimeters above the ground so that bold lilac roots do not overgrow the barrier.
My lilac tree was in the wrong location for several years and has developed an uneven shape. I transplanted it to a better, sunny spot in the fall. When and how can I trim the lilac?
With autumn you have chosen the perfect time to transplant an inconveniently placed lilac tree. This is also the best date for regular pruning. Since a lot of root volume is lost when changing locations, you can restore the balance between underground and above-ground growth at the same time. Shorten all shoots by at least a third and water regularly so that your lilac tree roots quickly.
Chinese lilac is my favorite because it doesn't form annoying runners. Is the shrub suitable as a privacy hedge? When did the hedge reach its final height of around 3 meters?
Indeed, Chinese lilac (Syringa chinensis) thrives without invasive runners. This property makes it very popular with home gardeners as a flowering privacy hedge. Thanks to their rapid growth rate, the bushes have reached a height of 160 to 180 centimeters within 5 years and offer a decorative privacy screen in summer. It usually takes 10 years to reach the final height of 200 to 300 centimeters. The prerequisite for the prognosis is that you limit the care of the cut to a thinning cut.