This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
As a southern type we have no record of the occurrence of Pennyroyal in early deposits. Its present distribution is Europe, N. Africa, and N. and W. Asia, or the North Temperate Zone. In Great Britain it grows in the Peninsula and Channel provinces, except in E. Sussex; in the Thames province, Anglia, except in Bedford; in the Severn province, except in Monmouth and Hereford; in S. Wales only in Glamorgan; in N. Wales in Carnarvon, Flint, and Anglesea; in the Trent province, except in S. Lincs; in S.E. Yorks, S.W. Yorks, N.W. Yorks, Durham in the Tyne province, and Lakes district. In Scotland it is found only in Ayr and Berwick, south of which it is gen-eral. It is a native of Ireland and the Channel Islands. In some counties it is only an escape. Careful search upon a stretch of heath-land or common-land, in which are scattered numerous little ponds and pools, will reward the botanist who is searching for Pennyroyal. It is rather local, but a common constituent of ericetal formations, and is usually to be found by pools in such areas.
It is a much smaller, less erect, terrestrial form of mint. The stem is more or less prostrate. The leaves are egg-shaped, acute, notched, bent back, with no flowers in the upper axils, smooth in England, in S. Europe densely hairy, a protection against too rapid transpiration.
Photo. Dr. Somerville Hastings - Pennyroyal (Mentha Pulegium, L.)
The flowers are lilac, in the axils, round, distant, many in a whorl. The regular calyx and the flower-stalks are downy each side, and the teeth are fringed with hairs, the throat being defended by hairs, and tubular. The nearly regular corolla is smooth inside. Complete flowers are less numerous than small female flowers.
Pennyroyal is 6 in. to 1 ft. high. It flowers late in August and September. The plant is perennial, propagated by division.
The flower is arranged on much the same plan as M. arvensis, and it is likewise prostrate, and less visited by insects. The flowers are proterandrous or proterogynous the anthers or stigma ripening first. The corolla is smooth within and hairy on the exterior. The throat is closed with hairs. The equal stamens are erect.
The nutlets are free, and are dispersed when ripe around the parent plant. It is a humus-loving plant, and requires a peaty soil.
The name Pulegium, Pliny, is from pulex, a flea. Pliny says that fleas are killed by the odour of the burnt blossoms.
Pennyroyal is called Brotherwort, Churchwort, Pudding Grass, Hill-wort, Lillie-riall, Lurkey Dish, Flea Mint, Organ, Organy, Pudding Herb, Pulicall. It is called Pudding Herb because it was used for flavouring black-puddings, and Pudding Grass because it was used in hogs' puddings. Coles says: "Penniroyall chopped and put into a bag-pudding giveth it a savoury relish".
Pennyroyal is aromatic and pungent in taste, and flavoured like camphor. It contains a volatile essential oil, obtained by distilling it. It was used as an expectorant and diaphoretic, for hysteria, whooping-cough, asthma, and is in use now. It was used as smelling salts in cases of fainting by the Romans. The blossoms, according to Pliny, killed fleas, as above. The use of it in puddings has not entirely ceased. In Chaucer's day it formed an ingredient of the almighty drug "save", and was employed to sharpen the eyes.
Essential Specific Characters: 247. Mentha Pulegium, L. - Stem prostrate, leaves ovate, sub-glabrous, crenate, flowers purple, in distant whorls, throat of corolla closed with hairs, calyx tubular.