As a beginner, should I purchase a mature or partially trained bonsai, or start from scratch?
Opinion 1) I think you should start from scratch. Your first attempts may never be ‘show quality’, but you can make a few mistakes without damaging a tree you paid for. It may take a bit longer to arrive at something that looks the way you want it to, but bonsai is (usually) not one of those instant gratification hobbies. If you get the proper book and some guidance, starting with some inexpensive nursery stock may yield some ‘instant bonsai’ which allows the beginner to learn, while allowing you to own something that looks like a ‘real bonsai’. Stay away from trees labeled ‘Bonsai’ in MOST discount stores. Numerous people have seen some discount chains with dead or dying seedlings planted in shallow trays with a solid mat of pebbles glued down over the soil. The trees had not been watered, and even if they were, the water couldn’t penetrate the ground-cover. They were marked $10.00… Opinion 2) The question should really be: Should I start from scratch with a small seedling, or with