Pennyroyal

What it is¶

Pennyroyal is a small, creeping member of the mint genus, with tiny oval leaves and, in late summer, whorls of lilac flowers stacked up the stems. It grows naturally in damp, seasonally flooded grassland and by ponds. Crush a leaf and the smell is mint turned up sharply, with a strong camphor and medicinal edge.

That smell comes from pulegone, a compound that dominates pennyroyal oil and is responsible for both its flavour and its toxicity. The leaf in small culinary quantities has a long history of use in Iberian and older European cooking; the concentrated essential oil is a serious poison and has caused deaths (see Health and safety).

The name comes, via Anglo-Norman and Latin, from pulegium, related to pulex, "flea": the plant was used to repel fleas. In Portugal it is poejo, in Spain poleo. American pennyroyal (Hedeoma pulegioides) is a different North American plant with a similar scent and similar hazards.

Origins and history¶

Pennyroyal was one of the most popular culinary herbs of the ancient Mediterranean. The Roman recipes attributed to Apicius call for puleium frequently, alongside lovage, rue and coriander. In Greece, the barley drink kykeon associated with the Eleusinian Mysteries was, according to the Homeric Hymn to Demeter, flavoured with pennyroyal (glechon). See spices in the ancient world.

In medieval and early modern England, pennyroyal was a common garden and strewing herb, and one of its old names was pudding grass: it was a standard flavouring for hog's puddings and black puddings, blood sausages and stuffings. It was also widely used in folk medicine, including, dangerously, as an abortifacient. See medieval spice cookery and herbals and herbalists.

It dropped out of British cooking as spearmint and peppermint took over, and today it survives in the kitchen mainly in Portugal and Spain. In Britain it has become scarce in the wild as its wetland habitats have been drained.

Flavour and aroma¶

Pennyroyal tastes like a sharper, more camphorous spearmint, with a slightly bitter, resinous finish and less sweetness. It is noticeably stronger than garden mint, so less is needed. Dried pennyroyal keeps its pungency well.

In the kitchen¶

Use pennyroyal as a seasoning herb in small amounts: a few sprigs to a pot, not handfuls.

• Açorda alentejana. The best-known dish. This bread soup from the Alentejo region of Portugal is made by pounding garlic, salt and a big handful of herbs, usually coriander and, in many households, poejo, then pouring on boiling water and olive oil and adding stale country bread and poached eggs. Where poejo is used, a small handful of sprigs is typical for four; coriander does most of the work.
• Other Portuguese uses. Poejo flavours fish and bread soups, the sopa de poejo of the Alentejo, and a sweet herbal liqueur, licor de poejo.
• Spain. Poleo is best known as a tea: poleo menta, a mint infusion drunk after meals, is served in cafés across Spain (commercial blends usually combine pennyroyal with other mints). In some regions it flavours migas (fried breadcrumbs), and country stews.
• Puddings and stuffings. For a historical black or white pudding, the old English use, a small amount of finely chopped pennyroyal went in with thyme, savory and black pepper.

Buying and storing¶

Pennyroyal is almost never sold fresh outside Iberia; cooks usually grow it. Sprigs keep for a few days in water or wrapped in the fridge. The leaves dry well; store them airtight and away from light for up to a year. Dried poleo is sold as a tea in Spanish and Portuguese grocers. See drying herbs.

Substitutes¶

Spearmint with a pinch of oregano or thyme gives a similar sharp, herbal mintiness, and is the safer choice in any case. In açorda, simply use more coriander. For tea, ordinary mint is the obvious swap.

Pairs well with¶

Bread, eggs, garlic, olive oil, coriander, salt cod and other fish, pork and blood puddings, chickpeas, thyme and savory.

Growing your own¶

Pennyroyal is hardy and easy, provided it has moisture.

• Position. Sun or light shade in moist, even boggy, soil. It suffers in dry, hot spots.
• Starting. Sow the fine seed on the surface in spring, or buy plants. It roots wherever its creeping stems touch the soil, so divisions and cuttings take easily.
• Uses in the garden. The creeping form makes a fragrant ground cover or a small lawn between paving stones that releases its scent when trodden on; there is also an upright form.
• Care. Cut back after flowering to keep it tidy. Like other mints it spreads, but much less aggressively.
• Pets and children. It is a low-growing plant, easily nibbled; site it with that in mind.

Because it is scarce in the wild in Britain, grow your own rather than foraging it. See mint for the genus as a whole.

Health and safety¶

Pennyroyal is the most hazardous of the mints, and the difference between the leaf and the oil is critical.

• The essential oil is highly toxic. Pulegone is converted in the liver to menthofuran and other compounds that damage liver cells. Swallowing pennyroyal oil, sometimes in amounts of a tablespoon or less, has caused liver failure, kidney damage, seizures and death. Many cases involved attempts to induce abortion. The oil should never be taken internally or used as a food flavouring, and pennyroyal-based flea remedies have poisoned pets.
• Pregnancy. Do not eat pennyroyal, drink pennyroyal tea or use the oil in any form during pregnancy or when trying to conceive.
• Children, liver disease. Do not give pennyroyal tea to babies or young children, and avoid it altogether with liver disease.
• The leaf. Traditional culinary use in small amounts, a few sprigs in a pot of soup, is how the herb is eaten in Portugal and Spain. Strong or frequent teas and large quantities of leaf are best avoided, because they deliver meaningful amounts of pulegone.

See also¶

• mint
• coriander leaf
• thyme
• savory
• medieval spice cookery
• rue