Hedeoma pulegioides
Hedeoma pulegioides American false pennyroyal
Synonyms:
Melissa pulegioides
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American false pennyroyal is a small annual, growing 4 to 12 inches tall, with finely pubescent stems that are often branching but sometimes single‑stemmed. It grows on well‑drained, dry sites in full sun to part shade, often dispersing along with human disturbance. Typical of shale quarries, dirt roads, and dry meadows, it appears sporadically in open, low‑competition habitats.
Leaves are opposite, finely pubescent, and up to 1 inch long and ¼ inch across, varying from elliptic or oblong‑lanceolate to linear, with smooth margins that may appear slightly lobed. Seeds germinate once surface soils warm in June, and the tiny seedlings are easily overlooked. Plants often remain unnoticed until maturity in late July, when a flush of small, bilaterally symmetrical pale blue or purple flowers appears.
Flowers bloom from the axils, one to six per node, tubular and two‑lipped with five fused petals, and are visited by ants, small bees, and flies. The entire plant smells strongly of peppermint when disturbed or handled. Seeds persist on the plant late into winter, along with the calyx, which retains its uniquely medicinal scent.
Habitat & Range
Common in dry fields, pastures, open woods, disturbed uplands and roadsides. Prefers full sun and dry to mesic, well‑drained sandy, rocky, or loamy soils. Can tolerate partial shade.
Present throughout the state.
Range: Native from eastern Canada south through the eastern and north‑central U.S., from Minnesota and the Dakotas east to New England, and south to Georgia, Tennessee, and Arkansas.
Wetland Code: Not classified
Phenology
Flowers July to September.
Fruits September and October, may persist into December.
Characteristics
Inflorescence flowers arise singly or in very small axillary clusters (usually 1–4), each on a short pedicel with narrow bractlets at the base
Flowers bilaterally symmetrical; solitary or in tiny pseudo‑whorled axillary clusters; tubular, 2‑lipped, with 5 fused petals; white, often tinged blue or purple; about ¼″ long and ~⅛″ across
Leaves opposite, finely pubescent; lanceolate to ovate or obovate; margins entire or slightly lobed; petioled; 1” long, ¼” wide
Stems branched, occasionally single-stemmed; finely pubescent
Height 4 to 12 inches
Plant Codes
S-rank: S5 (Secure)
G-rank: G5 (Secure)
Ecology
Pollinated by ants, small bees and hover flies. The immature seeds (ovaries) may be fed upon by the Long-Necked Seed Bug (Myodocha serripes).
Humans are seemingly the best disperser of the seeds, as it readily moves with shale used in road construction and will frequently be seen in road margins or drainage ditches.
Plays an important role in dry, disturbed habitats by supporting tiny summer pollinators, contributing aromatic defenses to plant communities, and quickly colonizing newly exposed soils where few other species can survive.
Hedeoma pulegioides American false pennyroyal
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