Growing Pennyroyal: A Complete Profile
By Growing Home Greens Team · August 20, 2026
Pennyroyal is a mint, it smells wonderful, and it is the one herb here that comes with a serious health warning.
The toxicity is the headline
Pennyroyal oil is 80 to 92 percent pulegone. Small doses cause nausea, vomiting and abdominal pain; larger amounts cause multi-organ failure and death. It is an abortifacient and should not be used or handled extensively by anyone pregnant. It is highly toxic to cats and dogs, in the plant as well as the oil.
Historic use as a medicinal tea is exactly the practice that produced the case reports. Do not make tea from this plant.
What it is reasonable to grow it for
As a low aromatic groundcover it is pleasant, releasing a strong mint scent when walked on. That is a defensible reason to have it in a path or between pavers, away from pets, where nobody is going to harvest it.
It runs like the mint it is
Six to twelve inches tall and spreading well beyond that by runners, hardy zones 6 through 9. Container it or it takes the bed.
A note on sourcing: no extension service profile was found for this species, so the size and hardiness figures here come from general horticultural references and should be treated as indicative. The toxicity is well documented in the pharmacological literature.
Source: Mentha pulegium: A Plant with Several Medicinal Properties, a review of the pharmacology.
Companion planting guide for Pennyroyal · Find your planting dates
Typically viable in USDA zones 6-9. Not sure your zone? Look it up by ZIP code.
Mature height: 0.5-1 ft
Method: Direct sow: Direct-sow outside. It doesn't transplant well, or doesn't need the extra time indoors.
When to plant pennyroyal, by zone
Every zone pennyroyal grows in. Pick your zone in the header and it will be highlighted here. Each zone links to its full page.
| Zone | Start indoors | Sow or plant out | Harvest |
|---|---|---|---|
| 6a & 6b | Not usually | Apr 25–May 2 | First real harvest the season after planting |
| 7a & 7b | Not usually | Apr 10–Apr 17 | First real harvest the season after planting |
| 8a & 8b | Not usually | Mar 25–Apr 1 | First real harvest the season after planting |
| 9a & 9b | Not usually | Feb 15–Feb 22 | First real harvest the season after planting |
See exact start-indoors, direct-sow, and harvest dates for your zone →
How many Pennyroyal plants fit per square foot?
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 0.5-1 ft.
Where to buy pennyroyal seeds
True Leaf Market (each supplier's pennyroyal seeds)
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See it growing
Search YouTube for "growing pennyroyal" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
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Growing Pennyroyal: A low, spreading mint that is poisonous enough to be worth stating plainly, and toxic to cats and dogs.
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