I've tried putting out those metal tags you write on with charcoal but the names wash away, the metal rusts, and they get tromped on. Everyone asks me, what is this? Any good suggestions that have worked?
You can go to your garden supply and purchase plastic plant labels of various sizes....they're very inexpensive. Then label them with a Sharpie. (Permanent marker.)
Apart from replacing all your metal tags with plastic ones as suggested by ebaymom, you could also try doing a little memory test each time you hose the plants. Just work on three or four at a time and when they are firmly entrenched in the brain, move on to another batch. Depending on the size of your garden, you should become a gardening expert in a couple of months at most!