Carlton County, in Minnesota, sits in USDA hardiness zone 4a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with cabbage, cranberry, turkish rocket, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Carlton County holds more than one microclimate.
Soils and elevations shift across Carlton 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 Carlton County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Carlton County — the short answer
Carlton County, Minnesota: USDA zone 4a, about 155 days between hard freezes, across 551K 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 6
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~155
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 551K 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 Carlton County's average, not your lot's — a low corner or a tree line moves it. Against Carlton County's 155-day season, see what your own ground reads.
Heat in Carlton County
Across a year, Carlton County accumulates about 1,619 growing degree days above 50°F, about 646 fewer than the middle Minnesota county — ahead of 7 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 Carlton County
Across Carlton County, the ground is predominantly Alfisols, where Duluth, Ahmeek, and Greenwood are the most extensive named soil series. The soil is generally very poorly drained with a silt loam surface. Topsoil pH runs about 5.3–5.6, strongly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Very poorly drained
Prime farmland
8%
Hydric soils
35%
Soil still varies lot by lot — soil types explained.
How the ground varies across Carlton County
The USDA soil survey maps 31% of Carlton County as very poorly drained — but another 67% drains differently: 30% well drained, 15% somewhat poorly drained.
Duluth is the most extensive named soil at 11% of mapped acres, then Ahmeek (10%) and Greenwood (7%).
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 Carlton County
Each reading below is measured for Carlton 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 Carlton County are very poorly drained, in hydrologic group C — 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 Carlton County runs about pH 5.3–5.6, 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
MeasuredCarlton County runs about 155 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
MeasuredCarlton 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 Carlton County is in
Carlton County sits in the Northern Lakes and Forests — EPA Level III, inside the wider Northern Forests. One consistent ecological setting across the whole county.
What Grows in Carlton County
We scored all 1,086 plants against Carlton County's own USDA zone 4a and its own 155-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 Carlton County?
For most of the year, no — what changes is which crops still fit the days remaining. 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 6 — 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 Carlton County
- monarch butterfly122 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Carlton County
USGS estimates 1,046 lb of Glyphosate on Carlton County farmland in 2019, its largest by weight, ahead of 2,4-d (600 lb) and Chlorpyrifos (225 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 Carlton County — and how to grow with it.
We checked the federal record across Carlton County — 618 documented sites across 6 of the 9 source types we track.
The most significant on record: 1 Superfund site (none NPL-listed). 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 Carlton 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 Carlton County
Closest first, across Carlton County. Listing isn't leaking, and distance isn't exposure.
- 177625Nitrate · 2100 ft
- Mahtowa Gas Co/Como OilUnderground Storage Tanks · 0.8 mi
- 047N18W06AAB 01Nitrate · 0.9 mi
- 625377Nitrate · 0.9 mi
- COVENANT PARK BIBLE CAMP-SHOWERHOUSE TREATMENT (X3)Brownfields · 1.2 mi
- 484620Nitrate · 1.6 mi
- 447579Nitrate · 2.0 mi
- DOUG'S AUTO WORKSBrownfields · 2.1 mi
- 626445Nitrate · 2.4 mi
- Tjs Country CornerUnderground Storage Tanks · 2.7 mi
- 177607Nitrate · 3.6 mi
- Sonnys Service Oil CoUnderground Storage Tanks · 4.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Carlton 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 Carlton County.
Total Sites
618
across Carlton County
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
across Carlton County
Severity Distribution
across Carlton County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Carlton County, Nitrate runs higher than the national average — 276 sites across Carlton County. That's not a problem with your land — it's information about it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Carlton 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 Carlton County average
Your land is one point inside Carlton County
Everything above resolves to Carlton County as a whole — one PHZM band and one county frost record, read across 551K 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 Carlton County Average
Carlton County Average
- ●USDA Zones 4a, averaged across Carlton County
- ●One soil character for all of Carlton County
- ●Frost dates read at Carlton County's scale: May 4 to Oct 6
YOUR Parcel
- ✓Your exact zone, not Carlton County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Carlton County
Pull a site-specific report for your exact address in Carlton County, Minnesota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Carlton County averages can't show:
We read public map data around Carlton County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Carlton County average
How we know this about Carlton 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 Carlton County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Carlton County
When does frost risk typically end in Carlton County?
The last hard freeze (28°F) in Carlton 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 Carlton County?
Measured between 28°F hard freezes, Carlton County sees about 155 frost-free days — roughly May 4 through Oct 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 22, about 120 days.
Is the soil safe to grow vegetables in Carlton County?
The federal record around Carlton County is a meaningful one — 618 documented sites, mostly Nitrate entries (276), the nearest Nitrate record about 0.4 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 Carlton County's scale — its 4a band and its 155-day season. Your yard writes its own version of Carlton 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 Carlton County’s own scale
9 of the readings below were taken at Carlton County's own scale — its own ~155-day span between 28°F freezes, the 3 most extensive soil series mapped here and 618 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Carlton County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Carlton County's own 28°F hard-freeze dates and its ~155-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Carlton CountyUSDA NRCS SSURGO
- 618 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.4 miles outFederal environmental registers
- Carlton County's boundary and the 551,164 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~155-day seasonGrowable Ground crop-matching engine
- Carlton County sitting wholly inside the Northern Lakes and ForestsUS EPA Level III Ecoregions
- Open occurrence records documented in Carlton County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Carlton 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 Carlton County — the ~155 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 Carlton County's 551,164 acreswhy one lot differs from the next →
- Which of those 618 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 Carlton Countyread your own land →