I’ve heard some disagreement about whether selfheal is native or non-native and here is what I found out.
There are two varieties of the species, Prunella vulgaris var. lanceolata, which is American, and Prunella vulgaris var. vulgaris, which is Eurasian.
To distinguish between the two, take a leaf from midway up the stem. The American plant’s leaf will be 3 or more times as long as wide, and the base of the leaf will be rather wedge-shaped. The Eurasian plant’s will be smaller, at only 2-2.5 times as long as wide and the leaf base will be more rounded.
For herbalists this isn’t likely to matter at all, but for native plant nerds, it might. If for example you find that local fauna prefers the local variety, you might want to supply them with the American one.