Oslo, Minnesota, sits in USDA hardiness zone 4a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
On paper, cabbage, cranberry, turkish rocket, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Oslo, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Oslo lot. 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 Oslo — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Oslo — the short answer
Oslo, Minnesota: USDA zone 4a, about 163 days between hard freezes, across 237 acres of city.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 8
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~163
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 237 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Oslo's average, not your lot's — a low corner or a tree line moves it. Against Oslo's 163-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Oslo
Each reading below is measured for Oslo itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOslo runs about 163 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
MeasuredOslo 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 Oslo is in
Oslo sits in the Lake Agassiz Plain — EPA Level III, inside the wider Great Plains. That is read at Oslo's own centroid rather than borrowed from Marshall County.
What Grows in Oslo
Every plant below cleared Oslo's own zone 4a and its 163-day season. Each card opens that plant's Minnesota profile. How we score.
Is it too late to plant in Oslo?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 31; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 8 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
What's on the federal record near Oslo
Closest first, within ~10 miles of Oslo. Listing isn't leaking, and distance isn't exposure.
- DAHLSTROM MOTORSBrownfields · 250 ft
- FARMERS UNION OIL CO - OSLOBrownfields · 600 ft
- JIM'S BUMPER TO BUMPER INCBrownfields · 1600 ft
- Former Pederson Oil CoUnderground Storage Tanks · 1.2 mi
- Cenex Harvest StatesUnderground Storage Tanks · 1.2 mi
- 154-051-02DCCNitrate · 1.6 mi
- 155N50W29BAA 01 NordlingNitrate · 2.0 mi
- DAHLSTROM MOTORS INCBrownfields · 3.0 mi
- 155N49W31CBD 01 A NorlockNitrate · 4.5 mi
- 155-051-16ABANitrate · 4.8 mi
- 154-051-36DCCNitrate · 5.9 mi
- 155-051-08ABCNitrate · 6.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Oslo'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 Oslo.
Sources Checked
within ~10 miles of Oslo
Severity Distribution
within ~10 miles of Oslo
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Oslo, Nitrate runs higher than the national average — 26 sites within ~10 miles of Oslo. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Oslo
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 Oslo average
Your land is one point inside Oslo
Everything above resolves to Oslo as a whole — one PHZM band and one 28°F frost record, read across 237 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 city 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 local average.
Your Lot vs the Oslo Average
Oslo Average
- ●USDA Zones 4a, averaged across Oslo
- ●One soil character for all of Oslo
- ●Frost dates read at Oslo's scale: Apr 28 to Oct 8
YOUR Parcel
- ✓Your exact zone, not Oslo's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Oslo
Pull a site-specific report for your exact address in Oslo, Minnesota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Oslo averages can't show:
We read public map data around Oslo — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Oslo average
How we know this about Oslo
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Oslo’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Oslo
When does frost risk typically end in Oslo?
The last hard freeze (28°F) in Oslo typically lands around Apr 28, 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 19.
When is the first frost in Oslo?
The first hard freeze (28°F) in Oslo typically arrives around Oct 8, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 24, so the watching starts about Sep 8 — about 163 days after the spring freeze cleared.
How long is the growing season in Oslo?
Measured between 28°F hard freezes, Oslo sees about 163 frost-free days — roughly Apr 28 through Oct 8, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 19 to Sep 24, about 128 days.
Is the soil safe to grow vegetables in Oslo?
The federal record around Oslo is light — 36 documented sites across the 9 federal source types we checked, mostly Nitrate entries (26), the nearest Brownfields record under a tenth of a mile out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Oslo?
From about Sep 8 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 8 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 8. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Oslo's scale — its 4a band and its 163-day season. Your yard writes its own version of Oslo's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Oslo’s own scale
6 of the readings below were taken at Oslo's own scale — its own ~163-day season between 28°F freezes, the 237 acres it covers and 36 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Oslo's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Oslo's own 28°F hard-freeze dates, about Apr 28 and Oct 8 and the ~163-day span between themNOAA 1991–2020 Climate Normals
- 36 documented contamination sites on the federal record near Oslo, the closest Brownfields record under a tenth of a mile out from the town centreFederal environmental registers
- Oslo's boundary and the 237 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~163-day seasonGrowable Ground crop-matching engine
- The ecoregion at Oslo's own centroid, the Lake Agassiz PlainUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Oslo's 237 acres read through its county's SSURGO summaryfrom Marshall County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Marshall County
- The growing challenges every Minnesota grower plans around — written at state scale, so they stay on the state guidefrom Minnesota
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Marshall County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Oslo's 237 acreswhy one lot differs from the next →
- Which side of Oslo you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 237 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Oslo-wide figureread your own land →
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