Peppermint Leaf (Mentha piperita) is a (usually) sterile hybrid mint, a cross between watermint (Mentha aquatica) and spearmint (Mentha spicata). It is occasionally found wild with its parent species in central and southern Europe, but the first intentional crossbreed of watermint and spearmint was done in England. Being sterile, it spreads by rooting.
All Batches meet the above minimum standards at the time of manufacture