Unlikely — Zone Mismatch
pennyroyal (zones 6-9) does not overlap with Minnesota's zone range (3a-5a). Growing outdoors is unlikely without significant protection.
One zone short — what would close it
Pennyroyal is hardy to zone 6, and the warmest ground in Minnesota is zone 5 — 1 zone short. Planted in open ground it will not survive a Minnesota winter. To grow it here, grow pennyroyal in a hoop house or unheated greenhouse — its modeled 1.5-zone lift covers this gap.
A hoop house or unheated greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 6-9 (plant) against 3-5 (Minnesota). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Pennyroyal in Minnesota — the short answer
Pennyroyal in Minnesota: hardy in zones 6–9, full sun.
- Plant zones
- 6-9
- Not verified
- Minnesota zones
- 3a-5a
- USDA PHZM 2023
- Frost window
- Apr 19 - Apr 30 – Oct 10 - Oct 17
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 137 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 90 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Minnesota spans zones 3a-5a, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score pennyroyal against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your parcel report in seconds — read in full free for your first 14 days
Minnesota is not one climate
Minnesota’s winter-low ladder runs across 87 counties, from zone 3.5 in Beltrami County to zone 5 in Watonwan County. That is 15°F between the two counties’ average coldest night — the difference between pennyroyal overwintering in the ground and coming under cover.
The middle half of 87 counties runs 4–4.5 zones, with a median of 4.5 zones — a 1.5-zone span end to end.
Measured across 87 Minnesota counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where Pennyroyal Stands in Minnesota
Pennyroyal is rated for zones 6–9 — a cold floor USDA puts at -10 to 0°F. No Minnesota county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Minnesota winters, not about pennyroyal.
Below the zone 6 floor
87 counties
- Beltrami County · zone 3b
- Clearwater County · zone 3b
- Hubbard County · zone 3b
3 of 87 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Zone Comparison
Pennyroyal Needs
- USDA Zones: 6-9
- Sun: Full SunWe haven't confirmed this against a published source yet.
- Mature size: 1.3 ft tallWe haven't confirmed this against a published source yet.
- Picking window: ~90 days of harvestWe haven't confirmed this against a published source yet.
- Drought tolerance: LowWe haven't confirmed this against a published source yet.
Minnesota Has
- USDA Zones: 3a-5a
- Last Hard Freeze (28°F): Apr 19 - Apr 30
- First Hard Freeze (28°F): Oct 10 - Oct 17
- Annual Rainfall: 19-34 inches
- Common Soils: Prairie loam, Clay, Sandy outwash
Plant Zone Range (zones 6-9)
Preferred Soil pH
We haven't confirmed this against a published source yet.
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Pennyroyal in Minnesota
The frost window
Across Minnesota, the last spring hard freeze (28°F) clears between Apr 19 and Apr 30, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 163-day window you can count on — up to 181 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
When to start the seed
Those dates are when pennyroyal goes out, not when it starts. It is sown under cover about 6 weeks ahead, so counting back from Minnesota's late-side last freeze of Apr 30 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
Minnesota runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for pennyroyal, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether pennyroyal is a permanent planting or a replant-every-spring crop for you turns on your own zone within Minnesota; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — Lake County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says pennyroyal does not survive a Minnesota winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Minnesota under protection.
Growing degree days
Pennyroyal needs ~900 GDD (base 50°F) to ripen. We haven't confirmed this against a published source yet. The state median runs ~1920 GDD (from PRISM 1991-2020 climate normals), so Minnesota's typical season clears that easily.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Pennyroyal likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Minnesota's prairie loam and clay — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6 and 7 — worth knowing before you decide whether a Minnesota soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Minnesota site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost. pH range, preferred pH and drainage need: We haven't confirmed this against a published source yet.
Your land, not the state average
SSURGO maps about 34.6% of Minnesota as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Pennyroyal has low drought tolerance, so it is the fast-draining end that will cost you — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Minnesota soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant pennyroyal for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before pennyroyal goes in. What follows is Minnesota’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Minnesota — and how to grow with it.
We checked the federal record across Minnesota — 18,030 documented sites across 7 of the 8 source types we track.
The most significant on record: 172 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Minnesota carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds of imported, lab-tested soil grow well almost anywhere in the meantime.
Sources Checked
across Minnesota
Severity Distribution
across Minnesota
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Minnesota, CAFO runs higher than the national average — 1,010 sites across Minnesota. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Sources: EPA, USGS — 950K documented sites tracked nationwide across 8 federal source types.
What Else to Consider for Pennyroyal in Minnesota
Zone compatibility tells you about winter cold survival — but Minnesota growers also need to think about:
Extreme cold (zone 3a: -40F) limits many species
Short growing season (100-140 frost-free days)
Heavy clay soils in the Red River Valley
Growing pennyroyal here specifically
Pennyroyal rates to USDA zones 6–9 and takes frost damage on growing tissue around -10°F (FAO ECOCROP), but cold isn't the risk in Minnesota — wet is: with roughly 34.6% of its soils poorly-drained (SSURGO), soggy ground rots the crown.
Give pennyroyal a raised bed or mounded row with coarse amendment so its crown never sit wet. How to handle it →
What to actually do about these — and the constraints that apply to every Minnesota grower, not just pennyroyal — is covered on the Minnesota growing guide.
Timing shifts within Minnesota
Minnesota isn't one climate. In Lake County, the last hard freeze (28°F) holds until about May 14 — roughly 23 days later than the recorded state median — so plant pennyroyal to your county's window, not the statewide date.
County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Where in Minnesota Pennyroyal Is Zone-Hardy
Pennyroyal is rated for USDA zones 6–9. No Minnesota county reaches it. Even Watonwan County, the state’s mildest winter at zone 5a, sits below the plant’s zone 6 floor — so in open ground this one needs winter protection here, or a container that comes under cover.
Across those 87 counties Minnesota’s winter-low ladder runs from zone 3b in Beltrami County to zone 5a in Watonwan County — 1.5 USDA zones of spread, which is 15°F between the two counties’ average coldest night of the year. None of that range reaches the band pennyroyal needs, so here the statewide answer really is the answer.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. Pennyroyal’s zone 6–9 band: Not verified. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Pennyroyal draws honeybees, native bees, and butterflies (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, pennyroyal can only work that bloom inside Minnesota's frost window — roughly 174 days, opening after the last 28°F freeze (Apr 19 - Apr 30) and closing at the first (Oct 10 - Oct 17), per NOAA Regional Climate Centers ACIS, 1991-2020. Pollinator value: We haven't confirmed this against a published source yet.
Good to Know Before You Plant Pennyroyal
Pennyroyal is listed as toxic to dogs, cats (all) at a severe level. We haven't confirmed this against a published source yet. Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Recommended Pennyroyal Varieties for Minnesota
Minnesota publishes no state variety trial for pennyroyal, so we won't invent a "best for Minnesota" list. Choose types rated to your USDA hardiness zone (3a-5a), and confirm winter survival and drainage against your own parcel.
Minnesota Cooperative Extension
For Minnesota-specific cultivar recommendations, planting calendars, and pest pressure for pennyroyal, the canonical source is University of Minnesota Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Pennyroyal native to Minnesota?
No — the USDA PLANTS Database lists Pennyroyal as introduced rather than native in the Lower 48, so it is not part of Minnesota's native flora. It grows here as a garden plant; pairing it with a few Minnesota natives keeps local pollinators fed too.
Looking for plants that belong here? The Minnesota growing guide lists plants that USDA PLANTS records growing in Minnesota and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Pennyroyal in Minnesota
When can I plant Pennyroyal in Minnesota?
Minnesota's last spring hard freeze (28°F) clears between Apr 19 and Apr 30, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Pennyroyal, so this page does not state whether it overwinters in Minnesota and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Pennyroyal grown in across Minnesota?
Minnesota spans USDA hardiness zones 3a-5a (USDA ARS PHZM 2023). Pennyroyal is listed for zones 6-9, which do not overlap them, so there is no zone in Minnesota where this page can call outdoor growing reliable. A parcel report resolves your own address's zone.
How many frost-free days does a typical Minnesota site have?
A typical Minnesota site sees ~174 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Pennyroyal needs 90+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Lake, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Pennyroyal native to Minnesota?
No — the USDA PLANTS Database lists Pennyroyal as introduced rather than native in the Lower 48, so it is not part of Minnesota's native flora. It grows here as a garden plant; pairing it with a few Minnesota natives keeps local pollinators fed too.
How should I amend the soil for Pennyroyal in Minnesota?
Pennyroyal prefers pH 5.5-7.5 and well (dry spells) drainage. We haven't confirmed this against a published source yet. That sits in the common-ground band across Minnesota soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Pennyroyal actually grow on my specific land in Minnesota?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores pennyroyal against your address's mapped soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Minnesota
State-level data is a sketch. Your Growable Ground report scores pennyroyal against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Minnesota pennyroyal averages can't show:
We read public map data around Minnesota — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Minnesota pennyroyal average
Explore More
Growing guides for pennyroyal
Explore Minnesota county by county
Minnesota carries 87 counties with their own USDA zone — a sample of the growing pages for pennyroyal there:
Where else pennyroyal grows
Pennyroyal's zone band crosses state lines — these are the states closest to Minnesota in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Minnesota
Minnesota has a growing page for 752 plants — a rotating sample of the rest of the shelf.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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