Seal or not seal open interfaces on trees? For decades, the opinions of hobby gardeners have been divided and the opinions of experts differ. But if you look closely, you can clearly see that the tree is not that helpless at all. With excessive intervention, a person can even disrupt their recovery. It is sufficient to support the self-healing powers of the trees with tried and tested home remedies.

Risks of open cuts

If a branch breaks off or is deliberately sawn off, an open interface remains on the tree. This is like a wide open gate into the interior of the tree. Bacteria, fungi and moisture can penetrate and lead to diseases with serious consequences. The tree itself is evidently aware of this danger, because it tries to close the wound as soon as possible after the tree has been cut.

The self-healing reactions of the tree

Damaged wood does not regenerate, but rots over time. In order to minimize the danger that an open wound poses to the health of the tree, the tree reacts with two measures after the tree has been pruned:

  • Isolation in deeper layers
  • Walling up of the wound from the outside

The foreclosure process
The foreclosure process after a tree cut occurs in deeper layers, which are known as sapwood. The parenchymal cells found in it form an impermeable wall that prevents pathogens from penetrating into healthy wood. In addition, antibacterial substances are produced. But the deeper the cut goes, the fewer these cells are available. Fruit trees, for example, can only cope well with cut wounds up to 5 cm deep, even without wound closure.

Walling over the wound Wound
tissue, known as callus, grows from the edge of the wound and consists of young, divisible cambium cells. They cover dead wood and gradually close the open wound. This layer offers additional protection against invading pathogens. The overflow process is clearly recognizable by the typical bulge formation. Depending on the size and severity of the wound, it can last for years after the tree has been cut or it may not even come to an end.

Is wound closure a must?

While the tree’s natural wound closure takes years, the gardener can seal an open wound in a day. Aren’t the advantages obvious? No, because most wound closure agents on offer seal the interface almost airtight:

  • Wound closure prevents the interface from drying out quickly
  • a lack of oxygen significantly disrupts self-healing
  • in addition, cracks can occur in the seal
  • these let pathogens and moisture inside

Optimize cutting work – minimize risks

The tree owner can do a lot to promote good wound healing by performing the upcoming tree pruning as optimally as possible. These include:

  • the choice of the best cutting time
  • the right cutting technique
  • suitable tool

Best cutting time
The warm vegetation phase is the time in which the self-healing powers of the tree can best develop. The cambium cells that populate the wound find enough energy to grow while they rest during the winter months.

In order for cut wounds to heal faster and without sealing, the tree should be pruned in this growth phase if possible. Of course, this is not always possible and with every type of tree, because other influencing factors must also be considered when choosing the right carving time.

Correct cutting technique
An inexperienced cutting technique, cutting that is too deep and cutting measures that are too extensive are the most common mistakes that are made when cutting. They impair callus formation and thus hinder natural wound healing.

  • do not cut too deep
  • do not damage the astring
  • Keeping wounds small
  • never cut more than absolutely necessary
  • Make the cut at an angle so that water can run off better
  • If the branches have broken off, saw the frayed cut smooth

Suitable tools
Unsuitable tools often cause bruises or fray the interface. When cutting, however, only a clean, smooth cut should be left as it heals better and faster. This can only be achieved with a suitable tool that meets the following characteristics:

  • The right tool for every branch thickness
  • good quality
  • sharply ground
  • clean / disinfected

When does a wound closure make sense?

In some cases, the targeted sealing of open wounds with a wound closure agent is the better alternative.

  • seal in case of improper cut
  • when the cutting time is unfavorable for natural wound healing
  • if larger parts of the tree bark are cracked or damaged

But we also have a number of home remedies available for sealing, which at the same time support or at least do not hinder the self-healing powers of the tree.

Seal the damaged bark with clay and foil

If a large part of the tree bark is damaged or split open, there is a higher risk of drying out. New protective bark can then not or only insufficiently form. Sealing is necessary so that the exposed cambium layer does not dry out in winter. Two home remedies are good for this: clay and black foil. Below are the instructions in detail:

  1. Cut black foil appropriately. It must be large enough to encompass the trunk at the point of damage.
  2. Loosen and remove any loose parts of the tree bark by hand.
  3. Spread a damp layer of clay on all affected parts of the tree trunk.
  4. Quickly wrap the black foil around it so that the clay layer does not dry out. The foil must lie tightly on the tree.
  5. Secure the film to prevent it from loosening or loosening. Attachment with adhesive tape is ideal. Any fastenings that damage the tree are out of the question.
  6. Every two weeks the film is removed and the clay still adhering to the trunk is loosened.
  7. Let the tree trunk breathe for about half an hour before sealing it again with fresh clay and wrapping it with black foil.
  8. At the beginning of the new growing season in spring, the film and the clay can be completely removed. Now the self-healing powers of the tree are allowed to work.

Preparatory steps for open wounds
Before sealing open wounds after cutting a tree with one of the home remedies described below, you must prepare them accordingly beforehand.

  • Bevel the interfaces so that moisture flows off better
  • Smooth the edges of the wound with a sharp tool

It should also be noted that only the edges of the wound are sealed. The cut surface itself remains free.

Tree and candle wax

Tree wax is available in stores, but normal candle wax without perfume is also ideal for closing wounds.

  • after pruning in winter
  • immediately seal the open wound
  • with candle wax: light the candle and let the wax drip onto the wound
  • Wax protects against frostbite and pathogens
  • completely remove the wound closure in the spring

The wax layer seals the open wound airtight, but it can burst open again and again. So that no moisture and germs can penetrate through the cracks, the condition of the seal must be checked regularly and, if necessary, touched up.

Tip:  Only use tree wax or candle wax to close the wound. Other waxes lead to the drying out of the cambium layer, which is essential for healing.

Charcoal powder

You can easily make charcoal powder yourself from bits of charcoal. These are crushed in a mortar and then finely sieved. Charcoal powder offers several useful properties:

  • it has a disinfectant effect
  • promotes rapid drying of the wound
  • lets oxygen pass through for the necessary rotting

After the tree cut, the charcoal powder is generously sprinkled over the cut and lightly pressed on with (clean) fingers. Since it can be easily washed off by the rain, only rain-free periods are suitable for its application.

Tree tar as a wound closure

Tree tar is a natural compound made from oils and resins. On the one hand, it allows the tree to breathe, but on the other hand, it prevents moisture from penetrating. This type of seal is recommended for cuts from about 10 cm in diameter.

  • Tree tar is available in stores
  • renounce the not easy in-house production
  • strengthens the resistance of the tree
  • creates improved conditions for self-healing
  • Rotting is accelerated
  • Wound closure keeps moisture and germs out
  • protects against drying UV light

The disadvantage is that a wound closure made from tree tar takes up to two weeks to harden.

Mixture of clay and cow dung

The combination of clay and cow dung provides ideal conditions under which the cut wound can survive the cold and growthless time of the year and start its own wound healing well prepared in spring.

  • the layer protects against the cold
  • prevents dehydration
  • this wound closure is breathable
  • Cow dung provides valuable nutrients for new cells

The mixing ratio of clay and cow dung is 2: 1. In addition, some stone flour is added to improve the structure of the mix. Since this seal dissolves itself in its constituent parts over time, it does not have to be removed separately.


The fine pores of a large interface can be easily sealed with emulsion paint. Since it is breathable, interfaces can continue to dry even after sealing. This significantly reduces the risk of rot. At the same time, unwanted elements such as pathogens are left out.

Lime mixture

When slaked lime is mixed with cow dung and water, it develops properties similar to emulsion paint. Especially if the tree is pruned in winter, you can use it to optimally seal it against dehydration. For the mixture you will need 1 kg of slaked lime, 500 gr. Cow dung and 5 liters of water. It can also be used to coat tree trunks because it reflects sunlight and thus prevents cracks in the bark.

A tree cut always leaves open cut wounds through which moisture and pathogens can penetrate the tree. But he can heal these wounds himself and only needs our support in exceptional cases. For example in winter when your own strength is at rest. Wound closures from some home remedies can be easily combined with his needs.

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