American False Pennyroyal Packs a Minty Punch
Hedeoma pulegioides, an annual native to eastern North America, is a resilient plant with a distinct scent
American false pennyroyal (Hedeoma pulegioides) is an eastern North American native annual that is well-adapted to dry-ish sites in partial or open shade. Rather than putting down deep roots and competing with other plants in good soils, it produces lots of small seeds that fall into cracks in bare or rocky soils.
In the wild it is often found along pathways and, despite its small size, is noticed for its strong minty scent when brushed against or stepped on. In a garden setting, its scent acts as a repellent for many insects, including mosquitoes, ticks and gnats. It has been used as a companion plant for eggplant to repel flea beetles. In addition to American false pennyroyal’s use in the garden, its leaves and stems can be mixed with other herbs in potpourri.
In the wild it is often found along pathways and, despite its small size, is noticed for its strong minty scent when brushed against or stepped on. In a garden setting, its scent acts as a repellent for many insects, including mosquitoes, ticks and gnats. It has been used as a companion plant for eggplant to repel flea beetles. In addition to American false pennyroyal’s use in the garden, its leaves and stems can be mixed with other herbs in potpourri.
These wild plants are growing in rocky soil along the Appalachian Trail in Maryland.
Water requirement: Prefers dry to average soils
Light requirement: Prefers partial sun and open shade; will also grow in full sun but will need at least average levels of moisture to do well
Mature size: Forms a densely branched mound 8 to 12 inches tall and wide
Benefits and tolerances: Tolerates thin, rocky soils; flowers attract many small pollinators and beneficial insects, such as Halictid bees, small carpenter bees and dagger bees; like many members of the mint family, it is rarely bothered by mammalian herbivores
Water requirement: Prefers dry to average soils
Light requirement: Prefers partial sun and open shade; will also grow in full sun but will need at least average levels of moisture to do well
Mature size: Forms a densely branched mound 8 to 12 inches tall and wide
Benefits and tolerances: Tolerates thin, rocky soils; flowers attract many small pollinators and beneficial insects, such as Halictid bees, small carpenter bees and dagger bees; like many members of the mint family, it is rarely bothered by mammalian herbivores
Small flowers are held close to the stem.
Seasonal interest: The stems possess a strong minty fragrance from spring through winter; tiny blue flowers bloom in midsummer.
When to plant: Sow seeds outdoors in fall, or keep them in the refrigerator for early-spring sowing or starting under lights; seedlings can be transplanted relatively easily in midspring.
Distinguishing traits. American false pennyroyal has narrow elliptical leaves arranged oppositely on wiry stems. When disturbed, the leaves give off a pungent minty scent. The primary constituent of the scent is pulegone, the same as in European pennyroyal (Mentha pulegium), a relative.
The small blue tubular flowers are about one-quarter inch long and occur in the leaf axils. (The axil is the angle between the leaf stem and the stem the leaf is attached to.)
Seasonal interest: The stems possess a strong minty fragrance from spring through winter; tiny blue flowers bloom in midsummer.
When to plant: Sow seeds outdoors in fall, or keep them in the refrigerator for early-spring sowing or starting under lights; seedlings can be transplanted relatively easily in midspring.
Distinguishing traits. American false pennyroyal has narrow elliptical leaves arranged oppositely on wiry stems. When disturbed, the leaves give off a pungent minty scent. The primary constituent of the scent is pulegone, the same as in European pennyroyal (Mentha pulegium), a relative.
The small blue tubular flowers are about one-quarter inch long and occur in the leaf axils. (The axil is the angle between the leaf stem and the stem the leaf is attached to.)
American false pennyroyal is being used as an edging plant around a vegetable garden, along with spotted beebalm (Monarda punctata), another native plant.
How to use it. American false pennyroyal can be used as an edging plant, particularly along paths, where its scent is released anytime it is brushed against or stepped on. It is also a good filler plant in a partly sunny planting bed, sprouting up and filling in wherever there is bare soil. Its habitats include dry upland woods, roadsides, rocky woodlands and disturbed soils, such as along paths and railroad beds.
Branches taken from the plant can be used as insect repellents, particularly for mosquitoes, ticks and, especially, fleas. The branches can also be used in potpourri. The plant has been used in a variety of folk remedies; however, some of the components are metabolized to toxic substances that can damage internal organs. Do not consume plant parts or apply plant extracts directly to skin.
How to use it. American false pennyroyal can be used as an edging plant, particularly along paths, where its scent is released anytime it is brushed against or stepped on. It is also a good filler plant in a partly sunny planting bed, sprouting up and filling in wherever there is bare soil. Its habitats include dry upland woods, roadsides, rocky woodlands and disturbed soils, such as along paths and railroad beds.
Branches taken from the plant can be used as insect repellents, particularly for mosquitoes, ticks and, especially, fleas. The branches can also be used in potpourri. The plant has been used in a variety of folk remedies; however, some of the components are metabolized to toxic substances that can damage internal organs. Do not consume plant parts or apply plant extracts directly to skin.
As winter approaches, the leaves fall away, leaving stiff brownish-gray stems and calyx tubes that last nearly into spring.
These seedlings are two to three weeks old and are from a small clump planted the year before.
Planting notes. American false pennyroyal is easy to start from seed, and seeds can be purchased from several online sources, particularly those focused on herbs.
As this plant is a true annual, new plants need to start from seed each spring. Seeds can be started indoors under lights by sowing on or near the surface of a moist seed-starting soil. Germination happens best at or near 70 degrees Fahrenheit, or 21.1 degrees Celsius. Seeds do not require moist stratification, though it may enhance germination. I have always kept the seed packets in a refrigerator for a month or more before starting seeds indoors.
Seeds can also be started outdoors by sowing on the surface of bare soil in fall to late winter, but I’ve had better luck starting them indoors. Once established outdoors, existing plants will reseed themselves for the coming years.
Seedlings can be transplanted relatively easily. New seedlings that are exceeding their bounds in the garden can be transplanted or weeded out after they sprout in midspring. Seedlings are easy to distinguish by their intense minty scent and their slightly puckered triangular leaves.
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Planting notes. American false pennyroyal is easy to start from seed, and seeds can be purchased from several online sources, particularly those focused on herbs.
As this plant is a true annual, new plants need to start from seed each spring. Seeds can be started indoors under lights by sowing on or near the surface of a moist seed-starting soil. Germination happens best at or near 70 degrees Fahrenheit, or 21.1 degrees Celsius. Seeds do not require moist stratification, though it may enhance germination. I have always kept the seed packets in a refrigerator for a month or more before starting seeds indoors.
Seeds can also be started outdoors by sowing on the surface of bare soil in fall to late winter, but I’ve had better luck starting them indoors. Once established outdoors, existing plants will reseed themselves for the coming years.
Seedlings can be transplanted relatively easily. New seedlings that are exceeding their bounds in the garden can be transplanted or weeded out after they sprout in midspring. Seedlings are easy to distinguish by their intense minty scent and their slightly puckered triangular leaves.
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Garden BFFs? Why Your Vegetables Are Begging for Companion Plants
See more Great Design Plants
Botanical name: Hedeoma pulegioides
Common names: American false pennyroyal, American pennyroyal, mock pennyroyal, squaw mint, tickweed, stinking balm and mosquito plant
Origin: Its native range includes eastern Canada and Maine south to the northern half of Georgia and west to Kansas and eastern Minnesota.
Where it will grow: The seed is cold-hardy to at least minus 40 degrees Fahrenheit, or minus 40 degrees Celsius (USDA Zone 3; find your zone). As an annual, the plant dies back after setting seed in the fall, but returns from seed the following spring.
Caution: Do not consume plant parts or apply concentrated oils or plant extracts directly to skin.