Go to an arts and crafts store and see it they have a metal stamping kit.
Most of the arboretums and shrubbery commercial growers use them because they last indefinitely, and are easy to read even years later.
You just need a hammer and the raised lettering (like in an old newspaper linotype writer)/ perhaps estate sales/auction houses ?
I’m thinking of using that for something permanent, like the trees and bushes. But for things that are likely to change every year, I’m hesitant to spend that kind of money on metal labels. Especially given the sheer number of labels that I need!
But since ink and pencil don’t seem to survive more than a month on my land, I need something a little stronger. That was my logic in choosing pyrography this year.