You reminded me of it when you mentioned xenohormesis. I'd first thought that this was the process by which it extracts the medcinal, anti-cancer/anti-viral nutrients from the silver birch, but after a bit more consideration and a quick chat with grok, I don't think it is the same.

Anyway, when the tree gets inhabited by the chaga fungus, all of its great medicinal properties get concentrated in the fungus' 'conk,' which, made into tea, tastes amazing.