In the past, trees were usually cut in late autumn or early spring - during hibernation. Today, however, tree care experts advise you to do pruning in the growing season between March and September.
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Why? The summer cut is gentler, wound healing begins immediately and there is no risk of frost damage to the wound site. Nevertheless, cutting during hibernation has a few advantages over cutting during the growing season.
Winter pruning: tree pruning in late autumn / winter / spring
Since time immemorial, deciduous trees and other deciduous trees have been cut in early spring and late winter. A cut in suitable weather in January or February - i.e. well before budding - also has advantages:
- No leaves and therefore less nutrients are removed, so the tree is less weakened.
- the lack of foliage makes it easier to see where to cut
- Winter pruning stimulates increased budding in spring, as the reserves of all leaves have already been stored and after the pruning, more energy is stored in the roots for fewer buds.
- Disadvantage: At temperatures <0 ° C after the cut, the frost can penetrate the now open area and the branch or tree can be damaged.
So winter pruning brings one thing above all - wood growth. If I cut my young fruit trees that should still grow vigorously, this naturally has to happen in late autumn or in February at the latest. If I cut my 15-year-old maple, which is already getting too big for me, I should definitely do this in summer to remove leaves and not stimulate growth any further.
Summer pruning: tree pruning in summer / autumn
In tree care there is now a tendency to cut during the growing season. The tissues are already active and the "healing" (sealing off and walling up) of the wounds begins immediately. In addition, the cut trees react less strongly with new shoots, "water shoots", which are worthless for the canopy, occur much less often. Advantages of the summer cut:
- The tree is still in the middle of growth and can therefore close wounds faster.
- Many fungal pathogens are particularly active in late winter / spring, which is why an infection is more likely then.
- You will have a better view of which branches are taking away too much light and therefore need to be removed.
- The early thinning provides the tree with plenty of light and air before the winter break.
- There are no possible frosts that weaken the freshly cut tree.
- The growth is not additionally stimulated because leaf matter is removed - reactions to the cut (water shoots, unintentionally strong and numerous shoots) are less strong and chaotic.
- Growth is slowed down the most if you cut directly at the shoot - but this also weakens the tree the most.
The summer cut extends from March to the end of September. During this period, you can always cut, but there are certain unfavorable situations:
- Midsummer: In July, when it is particularly hot, it is not advisable to cut too heavily. Parts of the crown (the bark) that are normally in the shade are suddenly exposed to direct midsummer sun. It can lead to "sunburn", damage to the cambium and bursting of the bark. This applies especially to tree species with dark bark (e.g. cherry) or with very thin bark (e.g. red beech).
- Strong wind: If the trees are exposed to strong wind and weather events and if parts of the crown are suddenly exposed to this wind and weather, for example by removing individual long branches, it can happen that they break more easily due to the clearance.
- Old, weakly sprouting tree species: Here you want to encourage sprouting, so a winter pruning is justifiable.
Tree pruning is possible all year round, but you should know what you want to achieve. If you cut a tree in winter that is not supposed to get any bigger, you can simply cut it again in summer. If you want to make major corrections to fruit trees, you should definitely do this in summer, even if the tree is still to grow. Here the pattern is also divided between summer and winter.
Background: How does the tree react to the cut?
Trees don't heal their wounds - they heal bulkheads. When cut, the tree reacts like a branch break, at the break or interface the tissue inside is sealed off in such a way that neither air nor pathogens can penetrate deeper into the wood. The wood tissue that is separated from the healthy tissue by the partitioning dies off. In addition, the wound is closed again from the outside by a wall. The wood tissue that is separated from the healthy tissue by the partitioning dies off. The right incision now decides whether this process can run quickly and cleanly. In addition, there are bad and good “gravel” under the trees. If the tree does not succeed in sealing off and overburdening it, the slow decay begins from within,because decomposing microorganisms can spread in the tree and penetrate deeper and deeper into it.
Research on the subject has shown that trees can handle this process most efficiently in the growing season between March and September. If you cut during hibernation, larger areas of dead wood tissue are created. If you cut branches with a diameter that is too large (> 10cm or> 5cm in the case of poor "gravel"), the tree will not be able to build up the safe barrier between healthy and dead wood tissue.