Pennyroyal: A Minty, Bug-Repelling Herb

This type of mint isn’t in fashion now, but it was once used as a answer to an array of ailments from constipation to snake bites. Here, a bit about pennyroyal, a culinary herb, fragrance, and flea repellent.

A photo of a stand of pennyroyal. Look at those flowers!

Mint is one of my favorite flavors of ice cream. I’m also a fan of mint tea. This herb I’m especially fond of is used in a wide range of dishes, from curries to pasta and jellies to juleps. For Roman diners, the variety was similar: mint was added to salads, vegetable dishes like Alexandrian gourd, and sauces for boar, venison, wild sheep, hare, and pork.

All two dozen or so types of mint — spearmint, peppermint, apple mint, corn mint, and more — are grouped in one genus. Mint is part of a star-studded family, Lamiaceae, that includes loads of other aromatic herbs. Some are cooked with nowadays — basil, rosemary, thyme, marjoram, sage, savory, oregano — while others are mostly medicinal — lavender, catnip, and bee balm.

But one species of mint has been mostly lost to time: pennyroyal (Mentha pulegium). Native to southern Europe, western Asia, and northeastern Africa, it looks like its minty kin, growing 1-2 feet tall, with dimpled leaves and roundish pink flowers on straight stalks.

Largely obsolete today, pennyroyal only shows up in (to my knowledge) nine recipes in the whole of Apicius, a huge ancient cookbook. This might seem surprising, but even though it didn’t often make its way into Roman dishes, pennyroyal still found a place among the food.

Ovid, who lived around the end of the first century BC, wrote a notable fable about the importance of hospitality. Philemon, a Phrygian peasant, and his wife Baucis are the only in their town to welcome a pair of guests into their home. These strangers turn out to be Zeus and Hermes, disguised as farmers, who came to earth to test people’s faith. The whole region subsequently flooded, and the gods saved the two good hosts for their generosity and piety.

As they set the table for their unexpected guests, Philemon and Baucis decorated it with mint. Not only was this choice made because mint was held as a symbol of hospitality, but also because it smelled good. In addition to sitting on tables, mint was strewn on the dirt floors of homes and hung on the walls in antiquity to act as a natural air freshener.

Pennyroyal, being a type of mint, was thought to be wonderfully fragrant. Its aroma was one Pliny the Elder found invigorating:

It is for this reason that Varro has declared that a wreath of pennyroyal is more worthy to grace our chambers than a chaplet of roses…

The scent of pennyroyal was used as a deodorizer, as we can see, but Pliny also writes it could fend off the “injurious effects of cold or heat.” Like most herbs, pennyroyal was used as medicine. Pliny notes that it could cure twenty-five ailments, with wild varieties having seventeen more applications. Quite a lot!

The pennyroyal balms in Pliny’s Naturalis historia (Natural History) are mostly decoctions of the herb with other things. With wine, pennyroyal can act as a diuretic or can be applied to scorpion stings. Mixed with vinegar and polenta, it cures constipation, vomiting, and different pains when applied topically, and with water it stops nausea, chest pain, and stomach aches.

I’ve read that the internal use of pennyroyal can actually be risky — when ingested, it’s toxic and can cause liver trouble. Maybe some of those remedies aren’t such a good idea! But one application of pennyroyal, not a corporal one, is probably the most important and gives the herb its name – flea repellent.

The Latin word for the herb, pulegium, is believed to have come from pulex, meaning “flea.” Transferred into Anglo-Norman, pulegium became puliol, but real — “royal” — was tacked onto the end. Because of natural evolution and folk etymology (one foreign word being switched with a more familiar one), puliol real became “pennyroyal.” We’re able to see that our current word, broken down, basically means “royal pennyroyal.” Who knew?

As I’ve only encountered pennyroyal in one recipe so far, an herb spread called moretum, I haven’t made a regular formula for substitution. In that recipe, though, I just used regular spearmint.

Something to note is that Columella, the recipe’s author, had both mint and pennyroyal on his list. I’m not totally sure how their flavor profiles compare, but it seems like there was enough of a difference that distinguishing between them was necessary.

I’m hoping to get some pennyroyal going this spring so I can find out for myself. And should I ever find I have an especially bad flea infestation or need a posy to put on a table, I’ll know just what to try!

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