It is one of the most magnificent flowering shrubs in the summer garden: the summer lilac, also known as the butterfly bush. A pruning of the summer lilac is not absolutely necessary, but it makes sense. Because the following applies to the vigorous shrub: the more it is cut back, the more lush the flowers will be in summer. In contrast to the common lilac, the butterfly bush blooms on the annual shoots. With a cut, there is little risk that the tree will not bloom next summer.
Best time
Like almost all summer flowering shrubs, the butterfly bush forms the flowers on the new shoots. In late winter, this new shoot is still in the buds, while the shrub already bears inflorescences on the tips of the fresh branches in summer. With a slight pruning in late winter, you can therefore significantly increase the abundance of flowers.
Simply shorten the flowering shoots from the previous year. Prune your buddleia in mild weather, preferably as early as possible, but after the last severe frost. In this way, the new shoots are stronger and stronger than with uncut plants and you can enjoy the full bloom longer.
- When: late winter (February)
- after the last severe frost
- cut only on dry, cloudy days
- Shorten last year's shoots to two eyes
- only do it every three to four years
After pruning, the summer lilac will sprout again from the sleeping eyes. This costs the wood a lot of energy, so that the flowering starts later. So that the flowering does not shift to late summer, we recommend pruning by mid-February at the latest. In very mild weather, pruning can take place as early as the end of January. Due to the imbalance between the root mass and the crown, the new shoots are particularly long and strong and the flower umbels are numerous and large.
Pruning error
Under no circumstances should you only shorten the tips of the individual shoots every year! In this case, these branch excessively in the upper and outer areas. A very unfavorable growth form for shrubs, because in this case no sunlight comes inside and the wood only forms leaves on the outside.
tool
It is best to use sharp, clean pruning shears to cut the Buddleja so that the wood does not splinter or tear. In this case, the wound can only close poorly, so that in damp and cold weather there is a risk of bacteria, viruses or fungi penetrating and weakening the wood or even making it diseased. Should it get cold again after the cut, this is usually not a problem, because the butterfly bush is tougher than is generally assumed.
- for thinner branches: secateurs or pruning shears
- for thicker shoots (base shoots): pruning shears
- a chop saw may also be necessary
cutting techniques
There are different pruning techniques when pruning shrubs. A light pruning is carried out every year to keep the bush healthy, without interfering with the growth of the buddleia in a particularly shape-changing and radial manner. However, in order for the wood to grow handsomely over the years into old age, it is necessary to intervene a little more in the structure every few years.
cutting measures
Regular pruning measures
Vigorous summer bloomers like the Buddleja keep you healthy and vital by checking the shrub annually. In principle, branches that have dried out, are growing inwards or are lying on the ground are removed from all shrubs. If you cut above an eye, the branch will sprout again here. If you do not want a new shoot to grow at this point, you must keep the remaining branch stub as short as possible.
- remove dead and diseased branches
- Completely cut inward growing branches
- cut off one of two crossing shoots
- always cut off at the base
In principle, this cut can be carried out throughout the year. During the growth period, i.e. when the plant has leaves, it is easier to see whether a branch has dried up. In warm weather, the wounds can also heal faster.
model the crown
Although the butterfly bush grows without pruning, in the garden it should have an attractive shape and a compact crown. This can be influenced by a targeted cut. For a beautiful, homogeneous crown structure, you should therefore carry out the following cutting measures.
Here's how to do it:
- Vary cutting height in the shrub
- cut back some shoots
- leave other branches longer
- Only shorten particularly well placed branches by a third
taper cut
Over time, the shrub's shoots that originate at the base of the grove can grow too close together, interfering with each other. As a result, the buddleia becomes bare from below and from the inside with increasing age. In this case, a taper cut will help. Even after a radical pruning, the shrub will reliably sprout again and grow back beautifully bushy.
thinning cut
Even if the summer lilac gets too big for its location, you can lend a hand and cut it back significantly. Since the tree is very fast-growing, depending on the variety, it can become too large in just a few years. The shrub not only grows in height, but also spreads out in width, so that neighboring trees and shrubs can be threatened. Remove the oldest, heavily branched shoots at the base every two to three years after flowering. The bush will rejuvenate itself.
- snip some of the branches right at the base of the shrub
- shorten very thin base shoots
- cut stale, heavily branched branches at the base
- use pruning shears
- remove very strong branches with a chop saw
exception
An exception is the alternate-leaved summer lilac (Buddleja alternifolia). This tree shows a different growth character than the other summer lilac species. Buddleja alternifolia forms numerous small panicles of flowers in the leaf axils. What is decisive, however, is that this variant bears its flowers on the previous year's wood.
If you were to prune the shrub in spring, you would have to do without the abundance of flowers in summer and wait until the following year. For this reason, the summer lilac is rarely cut or only slightly thinned out after flowering.
radical cut
The summer lilac is very tolerant of pruning and can be radically pruned back to its basic structure if necessary. This measure is necessary, for example, for diseased trees. In this case, the shrub is radically shortened to 30 cm above ground level. Gardeners refer to this procedure as "putting on the stick".
In this way, previously dormant eyes can be activated at the base, the wood sprout again and grows denser and more branched than before. This cutting measure makes sense for all shrubs that are too close together or have been neglected for years. After the first radical cut, a re-cut once or twice in the following years is necessary.
- Cut all basal shoots down to two or three eyes
- completely remove all thin branches
- Cut out branches that are crossing and growing inwards
- only leave one or two side shoots per main shoot
- clip these after the first to second eye
If you do not want to do without the flowers for at least a year, you can spread this radical rejuvenation cut over three years. A third of the branches are cut every year using the method described above. It is best to distribute the cut over the entire shrub so that the shortened branches are hardly noticeable and there are still enough shoots with leaves and flowers left. The following year is the turn of the next third. After three years, the butterfly bush is completely rejuvenated.
Clean faded
In addition to the winter pruning of the butterfly bush, which serves to preserve and rejuvenate the wood, a gentle summer pruning, which takes place during the flowering period, is also recommended. In this case, however, you only remove the withered umbels of flowers.
This not only promotes subsequent branching, but also prevents the flowering shrub from forming seeds and being able to spread throughout the garden. The summer lilac is considered invasive. This means that the shrub, originally from Asia, can also displace native plants.
Young trees
Growth of young trees
If a young plant is set up correctly from the start, the gardener will save himself a radical pruning later. This is how the wood can be promoted and modeled in a targeted manner. With a young Buddleja, the weak shoots are removed in the first year after planting and the main shoots are severely shortened.
- Time: February (winter pruning)
- trim all thin and weak branches at the base
- Cut back all main shoots to 50 cm
- leave two outward-facing buds
- Shorten just above the eyes/buds
- Do not leave long stumps of branches (entry opening for pathogens)
A basic structure slowly builds up from the few, strong shoots that can be cut back every second or third year. Although the wood does not become so lush and large so quickly, it grows nice and compact from the start.