Hedeoma pulegioides, also known as pennyrile, American pennyroyal, or American false pennyroyal,[4] is a species of Hedeoma native to eastern North America, from Nova Scotia and southern Ontario west to Minnesota and South Dakota, and south to northern Georgia and Arkansas.

[5] It is a low-growing, strongly aromatic herbaceous annual plant from 15 to 30 cm tall, with a slender erect much-branched, somewhat hairy and square stem.

[8] The name pulegium was given to European pennyroyal by Pliny the Elder in the first century CE, for its use in repelling fleas (pulex, plural pulices) when it was spread on floors.

"[10] Upon ingestion, one of its components, pulegone, metabolizes into hepatotoxic metabolites that depending on dosage can lead to organ failure, seizures, and death.

At night, let penny-royal be scattered over the bed-covers, and laid under the pillows and bolster; strewing a large quantity between the sacking and the matrass.