St. Louis County, in Minnesota, sits in USDA hardiness zone 4a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
On paper, cabbage, cranberry, turkish rocket, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
St. Louis County holds more than one microclimate.
Soils and elevations shift across St. Louis County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around St. Louis County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
St. Louis County — the short answer
St. Louis County, Minnesota: USDA zone 4a, about 152 days between hard freezes, across 4.0M acres.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 3
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~152
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 4.0M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 4a is St. Louis County's average, not your lot's — a low corner or a tree line moves it. Against St. Louis County's 152-day season, see what your own ground reads.
One county, several growing seasons
St. Louis County's hard-freeze record runs about 152 days between freezes — but that is the county-wide average, and several towns inside it carry a markedly different season in their own 30-year record: Aurora at about 116 days (against the county's ~152).
Those are measured records, not estimates. If you garden in one of these pockets, plant against your own town's season rather than the county's ~152-day average.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record. Only held-out towns carrying their own record are named — a town with no record of its own is absent rather than estimated, and a county with nothing qualifying shows no spread at all.
Heat in St. Louis County
Across a year, St. Louis County accumulates about 1,405 growing degree days above 50°F, about 860 fewer than the middle Minnesota county — ahead of 2 of Minnesota’s 87 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in St. Louis County
Across St. Louis County, the ground is predominantly Inceptisols, where Greenwood, Rifle, and Eveleth are the most extensive named soil series. The soil is generally very poorly drained with a stony loam surface. Topsoil pH runs about 4.9–5.6, strongly acidic. Rainfall drains through hydrologic group A/D soils.
Soil order
Inceptisols
Drainage
Very poorly drained
Prime farmland
4%
Hydric soils
51%
Soil still varies lot by lot — soil types explained.
How the ground varies across St. Louis County
The USDA soil survey maps 32% of St. Louis County as very poorly drained — but another 59% drains differently: 22% well drained, 14% somewhat poorly drained.
Greenwood is the most extensive named soil at 13% of mapped acres, then Rifle (8%) and Eveleth (4%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in St. Louis County
Each reading below is measured for St. Louis County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across St. Louis County are very poorly drained, in hydrologic group A/D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across St. Louis County runs about pH 4.9–5.6, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredSt. Louis County runs about 152 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSt. Louis County sits in USDA hardiness zone 4a.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country St. Louis County is in
St. Louis County spans 2 EPA Level III ecoregions — Northern Lakes and Forests (93%) and Northern Minnesota Wetlands (7%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in St. Louis County
We scored all 1,086 plants against St. Louis County's own USDA zone 4a and its own 152-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Minnesota profile.
Is it too late to plant in St. Louis County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 3 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around St. Louis County
- monarch butterfly223 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in St. Louis County
USGS estimates 4,016 lb of Glyphosate on St. Louis County farmland in 2019, its largest by weight, ahead of Bromoxynil (2,585 lb) and 2,4-d (1,326 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across St. Louis County — and how to grow with it.
We checked the federal record across St. Louis County — 2,331 documented sites across 7 of the 9 source types we track.
The most significant on record: 18 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across St. Louis County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near St. Louis County
Closest first, across St. Louis County. Listing isn't leaking, and distance isn't exposure.
- ARCELORMITTAL MINORCA MINE INCBrownfields · 1.3 mi
- ArcelorMittal Minorca Mine IncUnderground Storage Tanks · 1.6 mi
- VirginiaPFAS · 2.1 mi
- Fraser Yard Section HqUnderground Storage Tanks · 2.5 mi
- City Of BuhlUnderground Storage Tanks · 2.5 mi
- University Mn Medical SchoolUnderground Storage Tanks · 2.5 mi
- Kelsey SectionUnderground Storage Tanks · 2.5 mi
- Coop Of KelseyUnderground Storage Tanks · 2.5 mi
- Former Swan GarageUnderground Storage Tanks · 2.5 mi
- Hwy 5 Convenience 9102Underground Storage Tanks · 2.5 mi
- Janzens StoreUnderground Storage Tanks · 2.5 mi
- Greaney StoreUnderground Storage Tanks · 2.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Louis County's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near St. Louis County.
Sources Checked
across St. Louis County
Severity Distribution
across St. Louis County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around St. Louis County, Brownfields runs higher than the national average — 1,146 sites across St. Louis County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in St. Louis County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the St. Louis County average
Your land is one point inside St. Louis County
Everything above resolves to St. Louis County as a whole — one PHZM band and one county frost record, read across 4.0M acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at county scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better county average.
Your Lot vs the St. Louis County Average
St. Louis County Average
- ●USDA Zones 4a, averaged across St. Louis County
- ●One soil character for all of St. Louis County
- ●Frost dates read at St. Louis County's scale: May 4 to Oct 3
YOUR Parcel
- ✓Your exact zone, not St. Louis County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in St. Louis County
Pull a site-specific report for your exact address in St. Louis County, Minnesota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Louis County averages can't show:
We read public map data around St. Louis County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Louis County average
How we know this about St. Louis County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where St. Louis County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about St. Louis County
When does frost risk typically end in St. Louis County?
The last hard freeze (28°F) in St. Louis County typically lands around May 4, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about May 25.
How long is the growing season in St. Louis County?
Measured between 28°F hard freezes, St. Louis County sees about 152 frost-free days — roughly May 4 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 19, about 117 days.
Is the soil safe to grow vegetables in St. Louis County?
The federal record around St. Louis County is a meaningful one — 2,331 documented sites, mostly Brownfields entries (1,146), the nearest Brownfields record about 1.3 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Everything above is measured at St. Louis County's scale — its 4a band and its 152-day season. Your yard writes its own version of St. Louis County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Minnesota's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at St. Louis County’s own scale
9 of the readings below were taken at St. Louis County's own scale — its own ~152-day span between 28°F freezes, the 3 most extensive soil series mapped here and 2,331 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- St. Louis County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- St. Louis County's own 28°F hard-freeze dates and its ~152-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in St. Louis CountyUSDA NRCS SSURGO
- 2,331 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 1.3 miles outFederal environmental registers
- St. Louis County's boundary and the 3,998,794 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~152-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions St. Louis County spans, Northern Lakes and Forests the largestUS EPA Level III Ecoregions
- Open occurrence records documented in St. Louis County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto St. Louis County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Minnesota grower plans around — written at state scale, so they stay on the state guidefrom Minnesota
What this page can’t tell you
- How the season shifts across St. Louis County — the ~152 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Louis County's 3,998,794 acreswhy one lot differs from the next →
- Which of those 2,331 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over St. Louis Countyread your own land →