Source: Magness et al. 1971
Pennyroyal is very similar in plant habit and culture to the other mints. The plant is prostrate and much branched, with small, round-oval leaves about an inch long. The leaves, either dried or fresh, are sometimes used for flavoring. The flavor of pennyroyal is more pungent and less agreeable than peppermint or spearmint. Oils of pennyroyal are obtained by distillation of the entire plant, as with the mints. Pennyroyal is grown more in northern Europe than in the U.S. No data are available on U.S. production, as it is included with other mints.