You can buy wood, plastic, and metal plant tags of every shape and size. I've tried many and am often disappointed. Writing on a plastic tag with a permanent marker sounds good, but every one I set out last year quickly faded in the sun and weather. Wooden markers seem to dry out or rot too quickly and metal ones are too expensive and can tarnish.
An easy option is to recycle a few of your aluminum cans and make your own durable tags that won't decay or lose the lettering. And they're practically free.
Begin by cutting the ends off of an aluminum can. I use a utility knife, but scissors will work too. You'll have a cylinder. The edges aren't normally sharp enough to cut you, but any metal burs will prick your skin. Be careful to avoid minor injury.
Take one of the aluminum strips and using the backward name as a guide write the backward lettering on the printed side of the can. An old ball point pen that doesn't write any more is perfect. You can use a sharp stick or a stenciling tool. The idea is to press the metal hard while you're writing.
To see a slide show of the entire process go to the "How-to" page.