A Valuable Lesson in Plant Identification from the People’s Apothecary Garden
What we’d originally thought to be Corsican mint (Mentha requienii; right) last Fall has turned out to be a lookalike plant called pennyroyal (Mentha pulegium; left). Both are in the mint family and possess its classic fragrance, but while Corsican mint remains a creeping plant often used as a ground cover, pennyroyal only mimics this growing pattern in the winter when it is dormant.
Corsican mint can be seen to have smaller smooth, rounded, and slightly thicker leaves, while pennyroyal grows more pointed, slightly serrated classic ‘mint’ leaves. Their differences become most apparent in the late spring, when pennyroyal will begin to grow tall shoots, while Corsican mint retains its creeping growth pattern. Their flowers in early summer are also distinctly different; while both are purple/white, the flowers of Corsican mint are very small with four distinct petals, while pennyroyal grows round, spikey balls of purple flowers along its new shoots.
Although pennyroyal has been used traditionally in medicine, modern studies have show it to have possible toxic effects on the liver, and it should not be ingested. Topically it can be used as an effective insect repellent, however we are planning to remove it from the Apothecary Garden come fall to avoid any confusion between it and our other edible mint varieties.
Let this be a reminder to all to be very careful with all plant identifications, and to not consume anything until you are absolutely certain of them!