So, what is the difference between Spearmint, Peppermint and Water Mint? Apparently it’s not a simple matter. You think it would be, given the popularity of chewing gum, but the plant taxonomists like to put a wrinkle in everything.
Spearmint (Mentha spicata) is an introduced species in Indiana. Water Mint (Mentha aquatica) is also an introduced species. Try to find Peppermint in a field guide and it will be missing, because it is now considered to be a cross between Spearmint and Water Mint.
Apparently, Peppermint has confused everyone since the beginning. Linnaeus treated it as a species – Mentha piperita. Somebody somewhere along the line decided that it was a cross between Spearmint and Water Mint and so put the ‘x’ in the scientific name.
The problem now is what to call it. Since it’s not a species, the field guide people don’t want to put it in their books, but it’s out there anyway, so what to do? Answer … call it Water Mint! Or, call it Peppermint! Or, don’t put it in there since it’s not a species! Sheesh, poor Peppermint, it gets no respect.