When should I prune my walnut tree?

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Dear Mr. Kötter, we have a very old and large walnut tree, the branches of which reach out over the shed roof and urgently need cutting. At what time of year should we prune back the tree? I have heard that walnut trees shouldn't really be pruned at all.

The GARDENA gardening expert

Dear Ms. S., you can prune back your walnut tree. The professional world is merely divided on the best time at which to conduct the pruning. The reasons for this are: If you are too late when pruning back your tree in the winter, the cut wounds will bleed. You should also observe that the younger branches of walnut trees are hollow. The danger here is that water runs into them after the cut, which could assist rot. 

Again, the correct time for pruning is crucial here. In my experience, the best time is in summer, at the end of July. After the end of the length growth, the thickness growth now begins in the branches, and wounds seal more quickly. The larger the wound cross-section, the longer the healing takes. However, I generally do not use artificial bark to seal wounds on walnut trees (should you do so, please ensure careful, continuous inspection of the wounds and their subsequent care). However, it is best if the wounds dry themselves. 

Dear Ms. S., now you have understood what the issue here actually is, cut any branches which are causing you problems after the 21st June. Cutting with a saw produces improved wound healing; you should smooth the cut edges carefully with a knife. Cut the surroundings clear so that the wounds remain well-ventilated and dried over the next years until the wound has sealed. The issue of wound rot is not completely prevented, but substantially reduced in this way. You should conduct inspections every few months should you seal the wound with artificial bark in order to be sure that the wounds heal.

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