We are zone 6/7 but I think most of these are cold hardy...some of these are medicinals some not and all either naturalized or growing wild here....curly (yellow) dock, self heal, dead
nettle, plantains, oregano, feverfew, sundrops, purslane, iris, daylilies, jonquils, crocus, st. Johns wort, scull cap, vincas, strawberries, violets, star of bethlehem, sedums, thymes...these are all growing in various areas in our 'yard' without much attention from us. If you could have taller things...echinaceas (I think there are some shorter cultivars), black eyed susans, evening primrose, golden rods, new england aster, shruby st John's wort......so much more fun than a lawn:)
...spring beauties, bluets, little goats beard,....hop clovers.....
edit to add...daisys, dianthus, buttercups, love in a mist,
rose campion, comfrey...