Hedeoma pulegioides aka American False Pennyroyal

Hedeoma pulegioides, or American pennyroyal, is a small annual. It belongs to the mint family, Lamiaceae. Its native range spans eastern Canada and the north-central and eastern United States. It grows in a temperate climate. Wild plants live in open woods and fields with dry soil. The RHS also lists the names mock pennyroyal and stinking balm. This species is not native to Britain or Ireland.

Plants reach about 1 foot (0.3 metres) tall. They spread about 0.7 feet (0.2 metres) wide. Their compact form suits small beds and containers. The leaves have a strong mint-like scent and taste. This scented foliage gives the plant value near garden seats. It also suits the sunny edge of a woodland garden. Flowers appear from July to September. Each flower has both male and female organs.

Choose a sunny spot with soil that drains well. The plant also grows in light or partial shade. Plants For A Future gives two accounts of soil preference. One favours acidic soil with low to moderate fertility. The other favours richer, sandy soil. The species can grow in sand, loam, or clay. It also tolerates poor soil and a strongly acidic reaction. Its stated pH range includes mildly acidic and neutral soils. It accepts dry or moist ground, rather than requiring wet conditions. Plants For A Future lists USDA zones 5–9. Sow seed in its growing site in spring or autumn.

The leaves have recorded uses in tea and as flavouring. Food makers have also used its essential oil for flavour. These uses do not mean all preparations are safe. Large amounts taken by mouth can be toxic. The extracted essential oil poses a particular risk. Pure oil can also cause skin inflammation on contact. This makes its history as a food plant worth treating with care.

Native North American peoples have long used American pennyroyal medicinally. Records describe uses for digestive complaints, colds, and menstrual problems. They also include uses linked to childbirth and abortion. These are records of traditional use, not proof of safety. The oil has uses in commercial insect repellents and cleaners. Records also describe the plant itself as an insect repellent. Plants For A Future does not flag it as weedy.