Biology

Pennyroyal is a perennial plant that flowers from June to October (1). Although the flowers seem to set seed well, and are self-compatible, seedlings have rarely been observed in the wild, and the plant tends to spread by rooting from the stems (2). This species was thought of as something of a 'cure-all'; it was a common feature of cottage gardens and was used as a treatment for many ailments including colds, and as a flea repellent. Indeed, the Latin name pulegium was given to the plant by the Romans who knew that the leaves kept the flea Pulex at bay (4).