Pennyroyal is a low-growing member of the Mint family used since ancient times in Rome for repelling insects, especially fleas, and making sick rooms smell better during Medieval ages. Its the smallest of the Mints with the same characteristic opposite leaves that are closet to the aroma of Spearmint and violet flowers that bloom in late Summer and Fall on a prostrate stem. Its late season flowering makes it a great choice for your Fall garden.
There are two main varieties of Pennyroyal: European (Mentha Pulegium L.) and American Pennyroyal (Hedeoma Pulegioides). The European variety is a spreading perennial with stems that creep along the ground. It originates from the Mediterranean region and came over with the European colonists. This variety is my favorite to grow in my garden every year as it always does well through Summer and Late Fall. American Pennyroyal thrives best in northern and eastern gardens of the United States. Both varieties of Pennyroyal can grow in USDA Zones 6a to 9b though my European Pennyroyal is doing well in my zone 5b garden. I’ve found this herb to be very hardy and versatile. If you leave for two days without watering it won’t die and on the wet end of the spectrum it can handle an exceptionally rainy day. Your pennyroyal will do best if planted in an area exposed to full sun though it can handle part shade. Just don’t grow any tall plants next to this aromatic herb as they’ll eventually cast too much shade on it.
I start my pennyroyal by cutting a 6 inch piece off the stem from the mother plant. It will also self-seed when the flowers have dried up if you don’t want to bother with taking cuttings. Plant the stem in fertile soils. My cuttings seem to do well in clay soils, too. It doesn’t need fertilizing, but occasional mulching is good to keep weeds from competing with your pennyroyal for soil nutrients.
Pennyroyal stays in bloom while most of your other flowers are starting to die off. Pennyroyal produces small purple to violet colored flowers going in a circular shape up the stem. They look especially attractive in borders, beds, and gardens alike while providing groundcover. The stems spread out and root pretty quickly so you may end up finding this herb invasive. To remedy the problem keep stems trimmed back to the length you want.
Harvest pennyroyal in late Fall after its been flowering for a few weeks. The plant contains a toxic compound called Pulegone so you don’t want to ingest any part of the plant. However, you can still dry the leaves to use in a potpourri thats good for repelling insects. To dry the leaves out simply hand the stems up in a warm, sunny location. You’ll know their completely dried out when the leaves easily crumble between your fingers.