Since the Renaissance, boxwood has occupied a special place in many gardens as a topiary. Later, in the first Baroque gardens from the second half of the 17th century, it continued to be artistically pruned into shape in many cases. In addition to creating extravagant green sculptures, however, pruning also serves the purpose of encouraging the slow-growing shrub to branch. If you want to prune your boxwood, the timing, the procedure and the tools are all important. We explain everything you need to know about it.
What does the pruning?
Although the boxwood borer has been giving boxwood a hard time the last few years, it still likes to be planted. Boxwood is excellent for topiary of any kind, but unfortunately it does not grow dense and compact on its own. It is therefore advisable to prune a boxwood even if it is not to be given a particular geometric or sculptural shape. Shrubs that are not pruned for years, often bald from the inside out and form long shoots without branching.
What are the species of boxwoods?
The genus of boxwoods (Buxus) belongs to the eponymous family of boxwoods (Buxaceae) and includes about 70 to 100 species. Boxwoods are evergreen and have small, usually slightly ovate leaves. When well supplied with nutrients, they show a rich, dark green color.
In the garden, usually two of the many species are used frequently. Very widespread is the common boxwood (Buxus sempervirens). This species grows between three and six meters high, depending on the variety. The many cultivars also vary in their growth and leaf shape. However, boxwood is not only popular as topiary, but also for low bed borders or hedges. Buxus microphylla, the small-leaved boxwood, is particularly suitable for this purpose.
The pruning methods
There are different pruning methods – depending on what is to be achieved. A distinction is made between topiary, maintenance pruning and (severe) pruning.
Wear gloves during any maintenance work on box trees, because the box is highly poisonous.
Topiary is done early in the year and is designed to create the basic structure. Provided that the boxwood has already been regularly shaped, you do not need to cut back to old wood for this. Just shorten the shoots from last year by a few centimeters. In the case of shaped shrubs, of course, a little more precision is required here. Therefore, it is better to cut carefully at first. Holes once created by too deep cuts can remain for a long time and are difficult to compensate.
Shaped cuts require practice and a good sense of proportion. To help, there are templates made of wood or wire mesh, which are available in different shapes. The cut is then applied to the side of the templates. But of course, even pruning a comparatively simple hedge shape can become treacherous. Check now and then to make sure you are still cutting straight by looking at the hedge from the side.
If you want to trim a boxwood that will retain its natural stature and just grow a little denser, it doesn’t have to be accurate. Trim the boxwood to give it a slightly pyramidal shape. You can achieve this by leaving the inner shoots a little taller and making them shorter on the outside as you cut.
Make your own ball shape template
You can easily make the template for cutting a boxwood ball yourself. Measure the diameter of your ball. Transfer this measurement in the form of a hemisphere on a cardboard paper and cut out the shape. Use the illustration above as a guide.
Maintenance pruning builds on topiary pruning at the beginning of the year. Growth from boxwood can result in irregular sprouts, which maintenance pruning can correct. These cuts are especially important for topiary because they promote dense growth. This involves pruning this year’s shoots evenly and only slightly. This pruning can be done several times a year, at four-week intervals. However, they are not mandatory for hedges and naturally growing forms. Here, an annual summer pruning is sufficient.
You can heavily prune an old boxwood that has grown sparsely to encourage it to branch again. However, some caution is required. Do not cut back the boxwood by more than a third at a time. There must still be enough foliage left so that the boxwood does not die of thirst.
Instead of completely removing many old shoots, it makes more sense to redirect them. The base of the older branch remains, but at a branching point to a fresher side shoot, the original branch is shortened. Thus, a new side shoot continues the original branch at that point. If you want to be sure that the plant will survive the procedure, it is better to spread pruning over several years and cut each spring.
When is the right time to prune a boxwood?
There are several, possible times when you can cut your boxwood. On the one hand, they depend on what kind of pruning should be done, and on the other hand, on what shape the boxwood gets. In principle, you may cut the boxwood from spring to autumn, depending on weather conditions.
When to use which type of pruning?
depending on the weather, approximately between the end of May and the beginning of April.
late frosts should no longer be expected
shortly before new shoots
Maintenance pruning: Summer
between May and September
Minimum interval of four weeks
before new shoots
On dry, slightly cloudy days to minimize the risk of fungus and burns
Use these tools to prune a boxwood tree
Although it often requires more work, manual hedge trimmers are preferable to electric ones for boxwoods. Electric hedge trimmers, in fact, have the shortcoming that shoots are often crushed rather than actually cut. This leads to fraying at the cuts, making them heal more poorly and allowing pathogens to enter more easily.
Hedge shears are also the best choice for box topiaries. There are also special boxwood shears for maintenance pruning. These can be used to accurately trim the thin new shoots. If it is not to be a hedge or other topiary, you can cut your boxwood with pruning shears or rose shears. It is generally important that the tool is sharpened and cleaned.
Where to put the boxwood cuttings?
Especially because the boxwood is quite susceptible to various plant diseases, if possible, no cuttings should remain on the ground. This is because pathogens can settle there and possibly colonize the plant. You can add the cuttings to the compost. If you shred it beforehand, the decomposition will be faster.