The illustrated growing guide
Pennyroyal
Mentha pulegium
Family Lamiaceae
Not a culinary mint, and this entry exists so it can be told apart from one. Pennyroyal is a Mentha, but it carries far more pulegone than peppermint or spearmint, and the difference shows up as human deaths from the oil, an infant killed by a home-brewed pennyroyal tea, and a dog killed by an oil application to its coat. It is also a listed invasive: CDFA rates it C and records it naturalised in 20 states including Missouri, spreading by rhizome and seed through seeps, ditches, marshes and vernal pools, allelopathic, and poisonous to grazing cattle. Nothing on this page is a growing recommendation. Note also that American pennyroyal (Hedeoma pulegioides) is a different plant sharing the name and the pulegone problem.
Full Sun to Part Shade
High water⚠ Invasive in parts of the USCheck your state before planting.
⚠ Spreads aggressivelyPennyroyal spreads aggressively — mints and their kin send out underground runners and are extremely hard to get rid of once they're in the ground. Grow it in a sunken pot or a fully contained bed, never loose in open soil.
From the print shop
The closest print we make
We don’t print Mentha pulegium. The closest we have is Mentha × piperita (“Peppermint”) in the Kitchen & Orchard collection — the same genus, Mentha, not the same species.
16 designsfrom $21.99white or black groundmatte poster, unframed
I
Overview
Will pennyroyal suit your garden, and what goes wrong.
Will it thrive where you are?
Enter your ZIP — we look up your USDA hardiness zone (2023 map) and check it against what pennyroyal actually needs.
Hardy inZones —Pennyroyal at a glance
Common pennyroyal problems
No pest or disease records on file for pennyroyal — which means the library has none, not that the plant has none.
II
Growing
Light, water, soil, propagation and the season’s jobs.
How to grow pennyroyal: light, water & soil
How to plant & propagate pennyroyal
III
The year
What pennyroyal asks for, month by month.
The pennyroyal year, month by month
BloomWhat each band means
- Bloom — flowers open — pollinators working, frost on blossoms is the danger.
The pennyroyal year as text
- Jan quiet month
- Feb quiet month
- Mar quiet month
- Apr quiet month
- May quiet month
- Jun bloom
- Jul bloom
- Aug bloom
- Sep quiet month
- Oct quiet month
- Nov quiet month
- Dec quiet month
These are the species' typical months — expect them a few weeks earlier in warm zones and later in cold ones. Watch the plant, not just the calendar.
IV
Ecology & uses
What it does for the garden, and what it is grown for.
Pennyroyal in the garden system
What pennyroyal is grown for
⚠ Toxic if eatenTOXIC — this is NOT culinary mint. Pennyroyal oil is about 85% pulegone, which the liver converts to menthofuran and which depletes glutathione; NIH LiverTox records that as little as one tablespoon (15 mL) can cause seizures, coma, acute liver failure and multi-organ failure, and describes a fatal case in an 18-year-old. Two infants given pennyroyal in a home-brewed herbal TEA suffered multi-organ failure and one died (Bakerink 1996, Pediatrics; PMID 8909490); a review of 18 cases found moderate to severe toxicity from about 10 mL of the oil (Anderson 1996, Ann Intern Med; PMID 8633832). A dog died within 48 hours after pennyroyal oil was applied to its coat for fleas (Sudekum 1992, JAVMA; PMID 1568929). California Dept. of Food and Agriculture reports it unpalatable and poisonous to cattle. NOTE: ASPCA has NO pennyroyal entry — only a genus-level Mint (Mentha sp.) listing, toxic to dogs, cats and horses, whose stated signs of vomiting and diarrhoea understate this species badly. Never eat it, never brew it as tea, and never put the oil on skin or on a pet.
Edibility, identification, and traditional-use notes here are general reference — not medical or veterinary advice, and not a claim that any plant treats or prevents anything. Medicinal ratings record how strongly a plant features in herbal tradition, nothing more. Never eat or dose a plant you have not positively identified. More on how to use this library.
V
Cultivars
Named varieties of pennyroyal, ruled as a catalogue.
Best pennyroyal varieties & cultivars
No named cultivars on file for pennyroyal yet — the species itself is what nurseries sell.
VI
Sources & plant ID
Where the care distinctions come from, and how the plant is filed.
Research basis
Sources behind this profile
No extension citations are attached to pennyroyalyet. The care figures below come from the library's own catalogue rather than a traced primary source.
Plant ID
VII
Where to buy
Third-party nurseries — not Story Thyme Farms.
Third-party nurseries, not Story Thyme Farms. Prices are theirs.
Story Thyme Farms may earn a small commission from these links, at no cost to you — it never changes what we recommend.
VIII
Questions
Pennyroyal questions, answered straight.
Is pennyroyal safe for kids and pets?
No — treat it as toxic if eaten. TOXIC — this is NOT culinary mint. Pennyroyal oil is about 85% pulegone, which the liver converts to menthofuran and which depletes glutathione; NIH LiverTox records that as little as one tablespoon (15 mL) can cause seizures, coma, acute liver failure and multi-organ failure, and describes a fatal case in an 18-year-old. Two infants given pennyroyal in a home-brewed herbal TEA suffered multi-organ failure and one died (Bakerink 1996, Pediatrics; PMID 8909490); a review of 18 cases found moderate to severe toxicity from about 10 mL of the oil (Anderson 1996, Ann Intern Med; PMID 8633832). A dog died within 48 hours after pennyroyal oil was applied to its coat for fleas (Sudekum 1992, JAVMA; PMID 1568929). California Dept. of Food and Agriculture reports it unpalatable and poisonous to cattle. NOTE: ASPCA has NO pennyroyal entry — only a genus-level Mint (Mentha sp.) listing, toxic to dogs, cats and horses, whose stated signs of vomiting and diarrhoea understate this species badly. Never eat it, never brew it as tea, and never put the oil on skin or on a pet. Site it accordingly if children or pets roam the garden. This is general reference, not medical or veterinary advice — call a vet or poison control if something has actually been eaten.
How do you propagate pennyroyal?
Rhizomes and seed.
Is pennyroyal invasive?
It can be invasive in some regions — give it room or a barrier, and check your state's invasive-species list before planting.
IX
Elsewhere
Where pennyroyal sits in the library.
Comfrey
Anise Hyssop
Echinacea
Mint