To help all beginners I'd like to start a thread about the biggest mistake you learned from as a beginner. I've made so many mistakes it is hard to chose, but:
* Learn when, how and how often to repot. Pretty obvious, but when I first started I used to repot several times a year (!) or else I would repot in the summer or some other bad time. I killed more trees with bad repotting than just about anything else. My favorite was when I would repot and stick the tree out in full sun immediately afterwards. I've gone years now without killing a tree from repotting - even in emergency cases.
* Learn when, how and how often to repot. Pretty obvious, but when I first started I used to repot several times a year (!) or else I would repot in the summer or some other bad time. I killed more trees with bad repotting than just about anything else. My favorite was when I would repot and stick the tree out in full sun immediately afterwards. I've gone years now without killing a tree from repotting - even in emergency cases.