Mentha

Mentha is a genus of plants, belonging in the family Lamiaceae. They tend to be very aromatic. They are rather tolerant to the climate conditions.
Probably the most known is the Mentha piperita (aka peppermint). It's crossbred from Mentha aquatica and spicata. It has no seeds, it spreads by rooting. It has several beneficial effects on health - among others on gastrointestinal tract and it also helps with concentration, but also calms the nervous system.
For Meldath: Sometimes it's mixed with tobacco to add the mentol flavor. On the other hand, I read about using it entirely instead of tobacco, so that you can quit your smoking habit.