Many plants require pruning to grow healthily. The ornamental maple does not tolerate pruning well, but it is not always possible to avoid it. The plant expert describes when and how to cut a Japanese maple and what you should definitely pay attention to.
To cut
Cutting stimulates growth, strengthens flowering and allows plants to thrive healthily. This is correct in most cases, but with ornamental maple a pruning can do more harm than good. But if it no longer grows densely, the height no longer meets your expectations, or if it needs to be kept in a certain shape, pruning cannot be avoided. The plant expert will tell you how to proceed when cutting.
need
In order to prevent damage, injuries and above all diseases from the ornamental maple, you should carefully consider whether this is absolutely necessary before pruning the plant. A Japanese maple grows very slowly and usually evenly. This basically means it would only need/should be pruned every few years if needed.
A case of need exists in particular if:
- shoots and twigs have dried out or died
- Shoots and branches show strong signs of frostbite
- the ornamental maple has fallen ill with wilt
cut damage
Every time you cut, you have to weigh up whether it is worth taking the risk of possible damage. The exception, of course, is the situation that urgently requires a cut, as described in the “Necessity” section. For example, a Japanese maple will "bleed" if you cut it at the wrong time. As a result, this Acer palmatum species loses vitality.
In addition, you cause injuries to the wood by pruning and clear the way for unwanted infections through the interfaces. Various pests are particularly attracted to freshly cut Japanese maples and, with a large-scale infestation, can usually not lead to the death of the maple plant, but can still cause major damage. The ornamental maple is weakened by cutting and is less able to cope with a pest infestation.
Possible diseases and parasite infestations include:
- Fungal infections such as red pustule disease and powdery mildew and downy mildew
- Bacterial Infections
- Wilting disease such as the so-called Verticillium wilt
- leaf tip drought
- Aphids and scale insects
- spider mites
cutting time
A very important factor when pruning an ornamental maple is timing. While almost all plants have the optimal pruning time in spring before the start of the growth phase and/or in autumn before hibernation, a Japanese maple should never be pruned in these times of the year.
cutting months
Autumn offers weather conditions that are too humid, so that the cuts on an Acer palmatum are not given enough time to dry properly before winter. The result would be frostbite. In addition, the so-called sap pressure is highest in autumn and early spring. If a cut occurs during this time, severe "bleeding" occurs. This in turn creates optimal conditions for the penetration of fungal infections and bacteria. For this reason, a Japanese maple should only be pruned between the end of May and the end of June at the latest when it is leafy. With the beginning of summer, the sap pressure slowly begins to increase again, so that thinning and pruning or topiary should definitely be done by then.
weather conditions
Choose a dry and preferably sunny day for pruning. The best time of day here is between late morning when the sun is a bit strong and early afternoon before it gets cooler/humid again in the evening. With the optimal weather conditions, you support faster drying of the interfaces.
cutting preparation
In order to keep the risk of plant damage as low as possible, it is absolutely necessary to only use hygienically clean cutting tools. Even on knife blades and scissors, bacteria or the like can settle again during storage after thorough cleaning, so it is advisable to always professionally disinfect the cutting tool just before use. You have various options to choose from.
heat
Hold the knife or scissors blades over a gas flame for about four to five seconds. A Bunsen burner, such as that used when camping, is best suited for this. The deeper you hold the tool in the flame, the higher the temperature and more reliable you will kill viruses and bacteria.
alcohol
A dip in 70 or 80 percent alcohol makes cutting blades hygienically clean if you leave them there for around two minutes. It should be isopropanol from the pharmacy or the drugstore. High-proof drinking alcohol is not suitable.
disinfectant sprays
Special disinfectant sprays are also available on the market, which are usually used for more hygiene in the home. However, sprays such as Sagrotan or Sterillium are effective against countless bacteria and viruses, such as those found in plants, which is why they are ideal for disinfecting pruning shears, saw blades and knives. The only important thing when using it is that you let the solution take effect for a short time and then let it dry. Do not wipe afterwards, because bacteria and viruses can be transmitted again via a rag or cloth.
pruning
If the time is right and a Japanese maple is to be pruned, it is not easy to start pruning and under no circumstances tearing out branches/shoots, but you should proceed as described in the following instructions.
maintenance/pruning
If a Japanese maple shows diseases, dead or dried branches/shoots, pruning is the only solution for undisturbed, healthy, dense and even growth. The optimal pruning is shown as follows.
- it is always cut off directly in front of the origin
- Always position the cutting tool vertically with a slight incline
- if possible, cut as far as possible from the branches, trunk and/or ground
- Cut off dried leaves from the remaining twig
- If the foliage is stunted, cut off entire branches from the point of origin
topiary
If a Japanese maple gets out of shape, gets too big or you want it to grow in a certain shape, the topiary helps, which usually only has to and should be repeated every few years. There are a few important details to pay attention to.
- never cut off more than a third of a branch
- limit yourself to "shape-disturbing" branches only
- always leave some leaves to maintain density
- for slender shapes, cut off branches no more than three centimeters before the trunk
TIP: For less width, instead of cutting the ornamental maple, you can use a wider ribbon/rope to shape it by tying it closer to the trunk. Do not use wire or flimsy binders that could scratch the wood.
Bonsai style
If a Japanese maple is to be raised in the style of a bonsai, smaller cuts are necessary every year. During the months of May and June, only the shoot tips are cut off. In this way, there will be finer branching and the leaf size will grow progressively smaller. These minimal cuts affect the maple plant less if the cut is made at the optimal time and you adhere to the points of hygiene and pruning as described in these instructions.
radical cut
A radical pruning is generally only appropriate if it is the last and only solution to a serious disease that would otherwise lead to complete death, such as Verticillium wilt. A Japanese maple is cut off about 15 to 20 centimeters above the ground. However, with a radical pruning, there is no guarantee that the Japanese maple will recover. Therefore, this cutting method should only be used if the plant is threatened with death.
TIP: In conjunction with a radical pruning and an infection rising from the soil, such as Verticillium wilt, it is advisable to replant the ornamental maple in fresh, disinfected soil to avoid reinfection.
post-treatment
After each cut, it is essential to seal the cut wounds. You can use various products for this, some of which also have a disinfecting effect. This measure reduces the risk of infections or bacteria entering the interior of the plant through the interfaces. They also help to dry faster, which also prevents the risk of rotting.
The following tools are suitable for sealing/disinfection:
- coal or sulfur powder
- Wax from the garden trade or normal candle wax
- resin
- special sealing paste from the garden trade
tool
Appropriate cutting tool
Choosing the right cutting tool depends primarily on how thick the object is that you want to cut off.
Tree/Pruning Saw
You probably won't be able to avoid a saw for reducing thick logs. However, since this leaves quite jagged wound edges, the use of a saw is only advisable if really no other cutting tool with a smooth blade can lead to the same goal.
secateurs
Conventional pruning shears are usually sufficient for cutting shoot tips and often also very dry branches.
knife
For thick branches, the use of a knife is preferable to a saw. The knife should not have any jags. These enlarge the wound area unnecessarily and are also very difficult to seal completely. For this reason, a Japanese maple should only be pruned with a very sharp cutting tool, which also prevents bruising on remaining branches.