Pennyroyal (Mentha pulegium) is a perennial herbaceous plant that belongs to the lamiaceae (mint) family. Superficially, it looks like a low-growing form of common garden mint. Like all members of the mint family, the stems have a characteristic square cross section. The leaves are opposite, slightly toothed at the margins, but smaller than garden mint leaves. Like all members of the mint family, the flowers are borne on dense, spiked, inflorescences at the end of the stems and these are within a characteristic range of violet to purple in colour.
History of Pennyroyal Use
Pennyroyal has been a traditional culinary herb in Europe since Ancient Roman times and a number of recipes in that most classic of Ancient Roman cookbooks, Apicius’ De Re Coquinaria calls for the use of fresh or dried pennyroyal as a flavouring.
Pennyroyal is native to the Mediterranean region of Europe and it was originally used by the Ancient Greeks to flavour wines. The Ancient Romans, who valued the plant for its culinary and medicinal qualities, spread it throughout their Empire. Even after the passing of the Roman Empire, it remained a commonly-used herb in Europe and was one of the healing herbs found in monastery gardens.
After the Middle Ages, plant’s usage declined appreciably during the Elizabethan and early Stuart periods. It was largely replaced by garden mint (a British native). It survived as a rare and medicinal plant. But though pennyroyal is referred to in a few recipes from the 19th century, its culinary use has died away almost completely today.
Other Uses of Pennyroyal
Despite its disappearance as a culinary herb, it is still occasionally employed as a herbal remedy. Pennyroyal tea, an infusion of the leaves, being the commonest method of ingesting it. The tea is employed as an emmenagogue (menstrual flow stimulant) and has been used historically as an abortifacient (for inducing abortions). The essential oil of Pennyroyal is also used as an aromatherapy oil.
Pennyroyal is a strong insect repellant and planting pennyroyal around the house will help repel mosquitoes, midges and other biting insects. Use of the oil on the skin also has insect repellent properties.
This said, pennyroyal should be used with extreme caution. It is a very toxic plant and contains pulegone, which is a highly-volatile toxin that affects liver and uterine function. Pregnant women should avoid all products containing or made with pennyroyal at all times. The essential oil of pennyroyal is even more toxic than the leaves and should only ever be used externally (and on unbroken skin).
It is always recommended that ingestion of pennyroyal is avoided today. But it you want to re-create authentic historic recipes that call for this plant, you can actually substitute for pennyroyal with the related plant, lesser calamint (Calamintha nepeta), as this has a near-identical sensory quality but without any of the toxic compounds.
To provide an example of a pennyroyal-based recipe, here is a modern redaction of a recipe for Game Meat Sauce derived from Apicius’ De Re Coquinaria (On Cooking):
Classic Pennyroyal Recipe
Ius in Venationibus Omnibus (Sauce for all Kinds of Wild Game) Recipe
Ingredients:
1 joint of game meat (either boiled or roasted to cook)
For the Sauce:
1 1/2 teaspoons freshly-ground black pepper
1 teaspoons dried rue, crumbled (or substitute dried and crumbled rosemary leaves)
1 teaspoons whole celery seeds
1 teaspoons juniper berries
1 teaspoons dried thyme1 tsp dried mint
1/2 teaspoons dried pennyroyal (but substitute lesser calamint to be safe)
2 tablespoons runny honey
100ml (2/5 cup) red wine
60ml (1/4 cup) game stock (or beef stock)
4 tablespoons liquamen (fish sauce)
2 teaspoons olive oil
Method:
In a mortar, combine the black pepper, rue (or rosemary), celery seeds, juniper berries, thyme, mint, pennyroyal (or lesser calamint). Pound these together with a pestle until you have a fine powder. Add the honey and work with the pestle until you have a smooth paste.
Mix together the re wine, game stock and liquamen (fish sauce) in a saucepan. Bring to a boil then whisk in the olive oil. Now work in the spiced honey paste. Simmer for 2 minutes to allow the flavours to meld then take off the heat and set aside to cool.
When the meat has cooked, slice and arrange on a serving dish. Pour over the cold sauce and serve.
Pennyroyal is a fascinating herb, but due its toxic qualities it should be used with extreme caution and only in small amounts. Even better, use lesser calamint as a substitute.
