Having identified the mystery tree that shot up at the bottom of my garden while I was ill, I now need to know how to prune it.It provides a welcome screen from the houses overlooking my garden that I would not have dared to plant had I been well enough to garden. I don't want to take all their light or push their wall over. However, I want to avoid the horrible twiggy effect that you see on trees that have been cut back hard. I'd prefer to take it out and try something else than mutilate it. Here's a photo.
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