Pennyroyal is a low-growing, strongly aromatic mint species belonging to the mint family (Lamiaceae). This attractive ground-covering perennial forms dense mats of light green leaves and produces numerous small lilac-pink flowers throughout the summer. When touched, the leaves release a strong mint fragrance. The young leaves can be used very sparingly, either fresh or dried, to flavour soups, sauces, stews, salads and herbal teas. Because of their strong, slightly peppery mint flavour, only a small amount is needed. Due to the presence of pulegone, frequent or excessive consumption is not recommended. Pennyroyal should not be consumed by pregnant or breastfeeding women or by young children.
Traditionally, pennyroyal was widely used in herbal medicine to aid digestion and relieve bloating, intestinal cramps and indigestion. It was also prepared as a tea to promote perspiration during colds. Today, internal use is discouraged because pulegone can be harmful to the liver and nervous system in higher doses. Externally, pennyroyal was traditionally used in herbal baths and compresses.
The leaves contain chlorophyll and can produce a soft grey-green to olive-green colour in natural dyeing and wool dye baths. However, pennyroyal is only rarely used as a dye plant because the colour is neither very intense nor particularly colourfast. In the past, pennyroyal was also placed among clothing, in stables and around the home to repel fleas, lice and other insects. Its strong aroma still makes it a useful natural insect-repellent plant. The nectar-rich flowers attract large numbers of bees, bumblebees, butterflies and other beneficial insects. Pennyroyal flowers from July trough September. Hardy perennial. Height: 25 - 30 cm.
Indoor sowing: April - May
Outdoor sowing: May - July
Germination: 10 - 21 days
Germination temp.: 18 - 22 °C
Sowing depth: ½ - 1 cm
Planting distance: 15 - 20 cm
Planting position: sunny - half shade
Flowering period: July - September
Harvesting period: June - September
Pennyroyal can be started indoors from early April until the end of May in large pots or seed trays filled with fine seed-starting compost. Sow the seeds approximately ½ - 1 cm deep and gently firm the soil. Water carefully afterwards to prevent the seeds from being washed away. Place the pots in a bright location at a temperature of 18 - 22 °C. Keep the compost evenly moist throughout the germination period, but avoid waterlogging. Under favourable conditions, the seeds will germinate within 10 - 21 days. Once the seedlings have developed several true leaves, they can be transplanted into larger individual pots if necessary. From mid-May onwards, once there is no longer any risk of night frost, gradually harden off the plants over the course of one week by placing them outdoors for increasingly longer periods each day. They can then be planted into the garden or into large containers.
Pennyroyal can be sown directly outdoors from May through July. Choose a sunny or partially shaded location with moist, humus-rich, fertile soil. Sow the seeds ½ - 1 cm deep and keep the soil moist and free of weeds during germination. When the seedlings are large enough to handle, thin them to a spacing of 15 - 20 cm. This provides sufficient room for the plants to develop into dense, healthy ground cover. Pennyroyal is easy to grow and adapts well to most soils. It performs best in a sunny to partially shaded location with moist, fertile soil. Unlike many other herbs, it tolerates wet conditions well and naturally grows along ditches, streams and other damp habitats. The plant spreads gradually by underground runners. Although it is less invasive than most other mint species, it is advisable to keep its growth under control in smaller gardens. Thanks to its creeping habit, pennyroyal makes an excellent ground cover. Water regularly during prolonged dry periods. Applying compost or an organic fertiliser once a year encourages healthy growth and abundant flowering.
Pennyroyal is a semi-hardy perennial. It tolerates light frost down to approximately –5 °C. In areas with colder winters, protect the plants with a layer of leaves, straw or mulch. Plants grown in containers are best overwintered in a cool, frost-free location during severe frosts. The leaves and young shoot tips can be harvested regularly from June to September. The leaves may be used fresh or dried. Regular harvesting encourages fresh new growth and helps keep the plant compact. Please note: Pennyroyal contains the compound pulegone. Use it only in small quantities and avoid consumption during pregnancy or while breastfeeding. During flowering, pennyroyal attracts large numbers of bees, bumblebees, butterflies and other beneficial pollinating insects. It is therefore not only a valuable culinary herb but also an excellent addition to a wildlife-friendly garden.
