Pennyroyal Mint
Pennyroyal Mint is a herb in the Lamiaceae family. It grows best in full sun to part shade with medium to wet moisture, and is listed for USDA zones 6-9. Plants reach harvest about 76–104 days after planting and sit about 12 inches apart.
Varieties
1 from True Leaf Market · sorted by days to maturity▸Pennyroyal76–104 days
Heirloom; Non-GMO; Container
90 Days to maturity. Mentha pulegium. Pennyroyal Mint Seeds. Non-GMO, annual or perennial, open-pollinated, heirloom. Suitable for growing in containers, garden plots, raised beds, and greenhouses. Pennyroyal Mint is a charming, aromatic perennial with fragrant green foliage and delicate lavender blooms—perfect for ground cover, containers, or pest-deterrent borders. Easy to grow from seed, it spreads enthusiastically and brings both beauty and functionality to your herb garden. While it has traditionally been used as a medicinal, herbal tea, and culinary herb, Pennyroyal can be toxic if the dose becomes large enough, so use caution with ingesting Pennyroyal. ~476,000 seeds/oz.
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Plant spacing
In a square-foot bed, space pennyroyal mint about 12 in apart — that fits 1 plant in each 1-foot square (1×1). Wider rows or containers space the same.
Plan your pennyroyal mint planting
Add pennyroyal mint to a free GardenDraft plan and get sow, transplant, and harvest dates computed for your ZIP code — with a drag-and-drop bed layout and reminders when it’s time to plant.
Start your free plan →At a glance
Storing & preserving
Stores well in the right conditions. Refrigerate stems in water, or wrap in a damp towel for a few days.
- Dry: Dehydrate or air-dry, then store airtight away from light.
- Freeze: Freeze chopped in oil or water in ice-cube trays.
General home-preservation guidance — for tested processing times and safety, follow the National Center for Home Food Preservation.
Growing timeline
Companion planting — with cited sources
From US/Canada cooperative-extension publications and peer-reviewed studies. Evidence-tier dots show how strongly each recommendation is backed: ●●● peer-reviewed mechanism · ●● extension consensus · ● traditional knowledge with a plausible mechanism.
Pairs well with (2)
- Common CabbageEvidence tier C: Traditional practice with plausible mechanism but limited empirical replicationpest-deter
Pennyroyal's pungent oils are traditionally used to deter ants, aphids and cabbage pests.
Timing: Spreads aggressively and is toxic if ingested (especially to pets/livestock) — contain it and keep clear of heavily harvested edibles.
Source: S7
- Common TomatoEvidence tier C: Traditional practice with plausible mechanism but limited empirical replicationpest-deter
Reported to deter aphids and ants near tomato; keep root-contained.
Timing: Spreads aggressively by runners — sink a bottomless pot or grow in a container rather than in the open bed.
Source: S7
Sources cited
- S7
- University of Minnesota Extension
Care & troubleshooting— extension-sourced, with citations
When to feed, prune & water
Attract beneficial insects and protect pollinators
Protection- Routine carePlant insectary flowers and tolerate light pestsstrong evidence — extension confidence
Grow a diversity of flowering plants (including small-flowered umbels and asters) to feed predators and parasitoids, and tolerate low pest numbers so natural enemies have prey to stick around.
- Routine careNever spray open bloomsstrong evidence — extension confidence
Avoid insecticides on flowering plants and apply any needed sprays in the evening when pollinators aren't active, and favor selective products over broad-spectrum ones to spare bees and beneficials.
Mulch to suppress weeds and retain moisture
Mulch- Routine careApply organic mulch around plantsstrong evidence — extension confidence
Spread a few inches of straw, shredded leaves, or compost around established plants (keeping it off stems) to hold soil moisture, suppress weeds, and moderate soil temperature; wait until soil has warmed for heat-loving crops.
Pinch leafy herbs to stay productive
Pruning- Routine carePinch tips and flower buds weekly· every 1 wk · ~10 wksmoderate evidence — extension confidence
Pinch the growing tips above a leaf pair and remove flower buds as they form. This keeps basil bushy and leafy instead of bolting to seed.
Trim and divide perennial herbs
Pruning- Routine careShear after growth flushes; divide every few yearsmoderate evidence — extension confidence
Shear perennial herbs like mint, oregano, thyme and sage after flushes of growth to keep them compact and productive, and divide crowded clumps in spring or fall to renew vigor and airflow. Go easy on fertilizer — lean conditions give stronger flavor.
Clean up debris and sanitize at season end
SanitationUnusual this time of year.
- Routine careRemove spent plants and fallen debrisstrong evidence — extension confidence
Pull and clear old plants, dropped fruit, and leaf litter at season end, since many pests and diseases overwinter in this debris; dispose of diseased material rather than composting it.
- Routine careClean tools, stakes, and cagesmoderate evidence — extension confidence
Wash and sanitize stakes, cages, and tools that touched diseased plants before storing or reusing them to avoid carrying pathogens into next season.
Harden off seedlings
ProtectionUnusual this time of year.
- Routine careGradually expose plants to the outdoors· every 1 days · ~2 wksstrong evidence — extension confidence
Starting about two weeks before transplanting, set seedlings outside in a sheltered, shady spot for a few hours and lengthen their time and sun exposure each day, avoiding windy days, to prevent transplant shock.
- Routine careEase back on water and transplant on a mild daystrong evidence — extension confidence
Water a little less during hardening (without letting plants wilt) to toughen growth, then transplant in late afternoon or on a cool, cloudy, calm day.
Something looks wrong?
Describe what you see on your pennyroyal mintand we'll rank the likely causes — most likely first, least-invasive fix first.
Japanese beetles
Pestmoderate- CulturalHandpick into soapy water· every 1 days · ~4 wksstrong evidence — extension confidence
In early morning when beetles are sluggish, knock them into a bucket of soapy water; daily removal also reduces the scent that draws in more beetles. Skip the lure traps, which tend to attract more beetles than they catch.
- CulturalCover plants past bloommoderate evidence — extension confidence
On crops that have finished flowering and set fruit, drape a row cover or netting to keep beetles off without blocking pollination during bloom.
Mint rust
Diseasemoderate- CulturalRemove infected leaves and stemsstrong evidence — extension confidence
Pick off and bag (don't compost) leaves and stems with orange pustules as soon as you see them. Avoid overhead watering and space plants so leaves dry quickly.
- CulturalCut mint back hard and renew the patchmoderate evidence — extension confidence
For a badly rusted patch, cut the planting to the ground and remove all debris to break the cycle, then divide and replant vigorous runners into fresh ground.
Powdery mildew
Diseasemoderate- CulturalImprove airflow + remove worst leavesstrong evidence — extension confidence
Cut out the most heavily coated leaves and thin for airflow; avoid wetting foliage late in the day.
- OrganicPotassium-bicarbonate or sulfur - label use only· every 1 wk · ~4 wksmoderate evidence — extension confidence
Apply a labeled potassium-bicarbonate or sulfur fungicide weekly per the label. No sulfur within 2 weeks of oil or in high heat.
Root rot from overwatering / poor drainage
Diseasemoderate- CulturalLet soil drain and water lessstrong evidence — extension confidence
Water root rots like Pythium thrive in saturated soil, so cut back watering, let the surface dry between irrigations, and water at the base rather than keeping soil constantly wet.
- CulturalImprove drainage and aerationstrong evidence — extension confidence
Use raised beds, loosen compacted soil, and add organic matter to improve drainage; remove plants that are already rotted since affected roots won't recover.
Slugs & snails
Pestmoderate- CulturalTrap, hand-pick at night, reduce cover· every 2 days · ~3 wksstrong evidence — extension confidence
Pick at night with a flashlight, set shallow beer traps, water in the morning so soil dries by dusk, and clear damp hiding spots.
- OrganicIron-phosphate bait - label use only· every 1 wk · ~3 wksmoderate evidence — extension confidence
Scatter a labeled iron-phosphate slug bait sparingly per the label; it's pet- and wildlife-safer than metaldehyde.
Spider mites
Pestmoderate- CulturalHose down and raise humidity· every 3 days · ~2 wksstrong evidence — extension confidence
Mites thrive in hot, dry, dusty conditions. Spray foliage (especially undersides) with water to dislodge them and reduce dust.
- OrganicInsecticidal soap or horticultural oil - label use only· every 5 days · ~2 wksmoderate evidence — extension confidence
Apply to undersides per label; mites resist many products, so soaps/oils are preferred. Not in extreme heat.
Whiteflies
Pestmoderate- CulturalRemove infested leaves and hose off· every 4 daysmoderate evidence — extension confidence
Pick off and discard heavily infested lower leaves and rinse colonies off undersides with a strong spray of water; yellow sticky cards help monitor numbers.
- OrganicApply a labeled soap or oil· every 1 wk · ~3 wksmoderate evidence — extension confidence
Apply a labeled insecticidal soap or neem oil per the label, covering leaf undersides; these reduce but won't eliminate whiteflies, so repeat as needed.
Aphids
Pestlow- CulturalBlast off with water· every 3 days · ~2 wksstrong evidence — extension confidence
Knock colonies off with a strong jet of water in the morning; repeat every few days. Light infestations rarely need more.
- OrganicInsecticidal soap - label use only· every 1 wk · ~3 wksmoderate evidence — extension confidence
For persistent colonies apply insecticidal soap to undersides per label. Avoid open flowers.