pennyroyal

(noun) Eurasian perennial mint have small lilac-blue flowers and ovate leaves; yields an aromatic oil. Synonyms: Mentha pulegium.

(noun) erect hairy branching American herb having purple-blue flowers; yields an essential oil used as an insect repellent and sometimes in folk medicine. Synonyms: American pennyroyal, Hedeoma pulegioides.