Figure 8.American pennyroyal (Hedeoma pulegioides)
Pennyroyal, mock pennyroyal, squaw mint, tickweed, stinking balm, mosquito plant.
American pennyroyal is found in dry soil from Nova Scotia and Quebec to the Dakotas and southward.
This strongly aromatic herb is of rather insignificant appearance, being a low-growing plant from 6 inches to a foot in height with a slender erect much-branched, somewhat hairy and square stem. The leaves are small, thin, and rather narrow. From July to September close flower clusters appear consisting of a few pale-bluish flowers. The entire herb has a strong mintlike odor and pungent taste.
The leaves and flowering tops are collected when the plant is in flower. The distillation of oil of pennyroyal is a limited industry carried on in scattered sections in the eastern part of the country.
Information on the extraction of volatile oils from plants is contained in the following publication:
Sievers, A.F. Methods of extracting volatile oils from plant material and the production of such oils in the United States. U.S. Dept. Agr. Tech. Bul. 16, 36 p. illus. 1928.