Pennyroyal

Description

Mentha pulegium, commonly (European) pennyroyal, or pennyrile, also called mosquito plant and pudding grass, is a species of flowering plant in the mint family, Lamiaceae, native to Europe, North Africa, and the Middle East. Crushed pennyroyal leaves emit a very strong fragrance similar to spearmint. Pennyroyal is a traditional folk remedy, emmenagogue, abortifacient, and culinary herb, but is toxic to the liver and has caused some deaths. European pennyroyal is related to an American species, Hedeoma pulegioides. Though they differ in genera, they share similar chemical properties. An annual to perennial plant with creeping or erect branched stems to about 40 cm in height. The stems are square in cross-section and can vary from hairless on some plants to densely hairy on others, with a green to sometimes red or purplish colour. The leaves, which grow in opposite pairs, are narrowly oval, 2–3 cm long x 1 cm wide, downy, sparsely toothed towards the tip, and taper into a short stalk. All parts of the plant are strongly scented when crushed but it does not have noticeable glands on its surface. The small (6 mm) flowers are densely packed in whorls at the nodes, widely separated, above pairs of leaf-like bracts. The calyx is a ribbed tube about 3 mm long, with 5 triangular teeth, the lower 2 being narrower and slightly longer than the upper 3; it is hairy both on the inside and the outside. The corolla has 4 mauve lobes or "petals" and is hairy only on the outside. The flowers are bisexual and have 4 long stamens, 2 (or all 4) of which project well beyond the corolla lobes. There is one long style which is forked to produce 2 stigmas, which also project from the flower. The fruits consist of a cluster of four brown, 1-seeded nutlets, each about 0.7 mm long. The flowering period starts in June and continues into mid-summer, although in northern countries it flowers rather later, sometimes as late as September, when it can fail to set seed. Its chromosome number is 2n = 20. The native range of pennyroyal is thought to be around the eastern Mediterranean, where it grows in damp meadows, around pools and in stream margins. It is, however, very widely established around the world, including North and South America, throughout Africa, Asia, Australia and New Zealand. In many places it is considered a troublesome weed of agriculture. Towards the northern edge of its range, as in Britain, it is considered to be rare and declining, except where introduced.