Closing a wound after pruning a tree has been a topic of discussion among experts and hobby gardeners for a long time. But in some exceptional situations, everyone agrees about sealing wounds. Various home remedies offer a good alternative to commercial products. The plant expert explains everything you should know about it.
Wound closure useful?
If the plant fibers are exposed after a tree pruning, they usually offer optimal access to the inside of the tree for fungi, bacteria, viruses and moisture. This increases the risk of serious diseases that can lead to the death of the tree. This is the theory that has existed for decades and is still often recommended in specialist books, especially in relation to fruit trees.
Self-healing powers instead of wound closure
In the 1980s, the American research scientist Alex Shigo questioned the sense of a general wound closure after a tree cut or “open” injuries. The results of his research work showed that trees usually have a strong self-healing system and that an external wound closure can even cause more damage than help. Healthy trees usually have a high resistance to injuries such as those caused by tree pruning, branches breaking off or bark and wood damage.
Wound closure can be harmful
Most tree wound sealing products seal almost airtight to prevent outside intrusion. It is precisely this circumstance that disrupts the self-healing process and can even significantly increase the risk of illness. This is due to the fact that caulking wound sealants do not let through the oxygen that trees need to heal themselves. Cracks can form in the seal, creating new entry points for infection and moisture.
Rapid drying of the wounds is prevented, which also promotes fungal infection and putrefaction.
For this reason, experts advise against general wound sealing and recommend doing this only in certain cases.
Trees heal wounds differently than humans and animals. This is where the callus layer overflows from the edges of the wound. Injured tissue does not regenerate, but encapsulates and rots. New, so-called cambium forms above a sealing line over the injured or rotted tissue. Cambium is fresh wood that seals wounds and makes injuries invisible.
Seal cuts – exceptions
Under certain conditions, sealing cuts on trees makes sense. In principle, problems arise that usually require wound sealing if the tree is pruned improperly and/or an unfavorable pruning time is chosen.
One of the most common mistakes made when pruning trees is using a blunt cutting tool. This usually results in frayed wound edges, which often form tiny tunnels far into the interior of the tissue and/or also expose tissue on the side, which significantly increases the risk of disease and makes natural regeneration more difficult/delayed.
Cutting time in the vegetation break
As a rule, trees slowly go into hibernation from autumn, during which they stop growing until the beginning of the new vegetation period in the coming spring. The problem is that the most optimal pruning for the preservation and shape correction of many tree species is in late autumn or winter. Due to the pause in vegetation, these trees cannot form a cambium to close wounds with new wood. As a result, the cold can get inside the tree, especially at the outer edges of the wound, and cause frostbite. In addition, dehydration in the area is possible, which means that no new cell layer can form. Sealing is therefore essential during the cutting period during the vegetation break.
It does not always require a laceration to require sealing. A burst or damaged bark, such as that caused by a car accident or deer browsing, is enough. If the bark is no longer undamaged and completely protective around the tree, there is an increased risk of drying out, especially in larger areas, which prevents the formation of new bark. However, wound closure is advisable here.
If the bark is damaged or split open, the affected area on the tree must be sealed. If one of the other two wounds applies, proceed as follows:
- Smoothing the edges of the wound with a sharp cutting tool
- make a sloping cut surface so that moisture can drain off
- only seal the outer edges of the wound
- the actual beveled cut surface remains free and is not sealed
Home remedies for injured bark
To prevent the exposed cambium layer from drying out if the bark has burst or otherwise been damaged in winter, two simple home remedies can help as ideal alternatives to commercially available products.
Clay and a black foil
Proceed as follows:
- Prepare black foil that can completely enclose the trunk in the area where the bark has come off
- remove loose pieces of bark
- apply moist clay to the affected area
- then quickly place the foil over the clay and wrap it around the trunk
- the foil should be stretched taut
- The best way to fix the foil ends is with adhesive tape – never nail or staple the foil to the tree
- Roughly every ten days, loosen the foil and let the tree “breathe” for about 30 minutes
- loosen any clay residues as well
- then put new clay on the affected area and wrap the area again with the foil
- At the beginning of the new vegetation period, remove the film and remains of clay – the tree’s self-healing powers will take care of the rest
Tip: Never use wax to close the wound. This promotes drying of the cambium layer and thus prevents the healing process.
Tree and candle wax as alternatives
Tree wax and candle wax offer two home remedies that can be used to seal cuts. When used properly, they form an airtight cover – at least until there are no cracks or the like caused by the weather.
Please note the following points when using it:
- Tree and candle wax protects against frostbite after extensive cuts in winter
- Check sealed surfaces regularly for cracks and damage and correct with new wax if necessary
- If cracks in the wax remain open, fungi, viruses and bacteria can penetrate and spread undisturbed
- Always apply wax immediately after the cut
- Before applying the wax, always ensure that no pathogens have been transmitted by cutting tools
- The tree and candle wax should be removed in spring at the latest, especially on larger wound areas, so that natural regeneration is not impeded/prevented
- Collect tree wax from your own tree stocks or buy it from specialist retailers
- Any type of candle without perfumes is suitable as candle wax
- Application : Light the candle and drizzle the wax onto the desired area
Clay with cow dung as a home remedy
A mix of clay and cow dung or cow dung is considered the best way to close the wound. The two components together place a layer on wounds that protects against the cold and at the same time prevent the open tissue from drying out, so that the tree can form new wood in the spring after winter pruning. This is additionally supported by the breathability. The cow manure/cow dung also supplies the damaged areas with valuable nutrients, which promote and accelerate new cell formation. This seal does not have to be removed, as the components degrade independently over time.
The mixture should be blended in the following ratio:
- 2/3 clay
- 1/3 cow manure/cow pats
- a handful of rock flour to improve the slurry structure
Charcoal powder is a common home remedy that is used after pruning a tree. It promotes rapid drying of wet wounds while allowing oxygen to pass through, allowing damaged tissue to decompose and make room for new cells. It also has a disinfecting effect. For this reason, the insert is equally suitable for frayed wound edges and cut surfaces. Charcoal powder is easy to make yourself:
- crush commercial charcoal with a mortar
- Alternatively : put the charcoal in a bag and break it into the smallest particles with a hammer – then sieve out the powder
- Sprinkle tree wounds generously with the powder
- Press down the powder with your fingers
- only use on dry days with weather forecast for rain and wind-free days (otherwise the powder will be washed off or blown away before it can take effect)
Sealing with tar should only be used on parts of the plant that are at least as large as a forearm. Tree tar is a natural agent that is open to diffusion and at the same time water-repellent.
It consists of natural components such as resins and oils. When sealing, it optimizes the conditions so that the tree can regenerate itself at the wound sites. Rotting is accelerated, resilience is improved and special protection against moisture from outside, mold and pest infestation and drying UV light is provided.
A disadvantage is that wood/tree tar takes around two weeks or more to harden. But extraction is not easy either, and harmful vapors can escape, which is why you should only wear appropriate protective clothing. For the reasons mentioned, it is advisable to buy ready-made tree tar from the trade and not to produce it yourself.
Emulsion paint has filling, binding and breathable properties. Especially in the case of large wounds, such as when tree trunks are cut, dispersion paint closes the open pores after a tree cut, so that nothing can get inside the tree from the outside. Due to the breathability, wounds cannot “sweat”. As a result, they dry better without provoking dehydration and minimize the risk of rotting.
Mixture of cow manure, lime and water
Similar to emulsion paint, a mixture of cow manure, lime, and water can be used to seal after pruning. Above all during the vegetation break, the mixture ensures that no drying out takes place, which prevents the formation of new tissue. The mixed components also prevent the formation of cracks, which often occur on trunks in winter when cold and warm sun alternate. The lime paint reflects the sunlight.
The preparation of the mixture is as follows:
- Mix about two 2 kilograms of slaked lime with 10 liters of water
- mix in about a kilogram of cow dung
- As an alternative to cow dung, you can also mix in clay or 500 grams of wallpaper paste