Onamia, 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.
Even in Onamia, 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 Onamia 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 Onamia — soil, climate, flood, and parcel records. How we handle your address.
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Onamia — the short answer
Onamia, Minnesota: USDA zone 4a, about 162 days between hard freezes, across 628 acres of city.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 1
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~162
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 628 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 Onamia's average, not your lot's — a low corner or a tree line moves it. Against Onamia's 162-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Onamia
Each reading below is measured for Onamia itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOnamia runs about 162 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
MeasuredOnamia 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 Onamia is in
Onamia sits in the Northern Lakes and Forests — EPA Level III, inside the wider Northern Forests. That is read at Onamia's own centroid rather than borrowed from Mille Lacs County.
What Grows in Onamia
Every plant below cleared Onamia's own zone 4a and its 162-day season. Each card opens that plant's Minnesota profile. How we score.
Is it too late to plant in Onamia?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Apr 3; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 1 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 10 — 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.
What's on the federal record near Onamia
Closest first, within ~10 miles of Onamia. Listing isn't leaking, and distance isn't exposure.
- T & J TireUnderground Storage Tanks · 100 ft
- District Forestry OfficeUnderground Storage Tanks · 200 ft
- Onamia Maintenance ShopUnderground Storage Tanks · 200 ft
- H & L Oil CoUnderground Storage Tanks · 200 ft
- NOBLE WEAR LTD - ONAMIABrownfields · 250 ft
- Gte #1507050Underground Storage Tanks · 600 ft
- ONAMIA POLICE DEPTBrownfields · 700 ft
- DOLLAR GENERAL STORE 19385Brownfields · 1200 ft
- MILLE LACS HEALTH SYSTEM HOSPITAL PHARMACYBrownfields · 1400 ft
- MAR TEK ELECTRONICSToxics Release Inventory · 1600 ft
- NOBLE WEAR LTDBrownfields · 1700 ft
- Mille Lacs Health SystemUnderground Storage Tanks · 1800 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Onamia'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 Onamia.
Total Sites
108
within ~10 miles of Onamia
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Onamia
Severity Distribution
within ~10 miles of Onamia
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Onamia, Nitrate runs higher than the national average — 56 sites within ~10 miles of Onamia. 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 Onamia
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 Onamia average
Your land is one point inside Onamia
Everything above resolves to Onamia as a whole — one PHZM band and one 28°F frost record, read across 628 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 Onamia Average
Onamia Average
- ●USDA Zones 4a, averaged across Onamia
- ●One soil character for all of Onamia
- ●Frost dates read at Onamia's scale: May 1 to Oct 10
YOUR Parcel
- ✓Your exact zone, not Onamia's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Onamia
Pull a site-specific report for your exact address in Onamia, Minnesota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Onamia averages can't show:
We read public map data around Onamia — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Onamia average
How we know this about Onamia
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 Onamia’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 Onamia
When does frost risk typically end in Onamia?
The last hard freeze (28°F) in Onamia typically lands around May 1, 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 22.
When is the first frost in Onamia?
The first hard freeze (28°F) in Onamia typically arrives around Oct 10, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 26, so the watching starts about Sep 10 — about 162 days after the spring freeze cleared.
How long is the growing season in Onamia?
Measured between 28°F hard freezes, Onamia sees about 162 frost-free days — roughly May 1 through Oct 10, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 22 to Sep 26, about 127 days.
Is the soil safe to grow vegetables in Onamia?
The federal record around Onamia shows 108 documented sites, mostly Nitrate entries (56), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Onamia?
From about Sep 10 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 10 (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 10. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Onamia's scale — its 4a band and its 162-day season. Your yard writes its own version of Onamia'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 Onamia’s own scale
6 of the readings below were taken at Onamia's own scale — its own ~162-day season between 28°F freezes, the 628 acres it covers and 108 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Onamia's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Onamia's own 28°F hard-freeze dates, about May 1 and Oct 10 and the ~162-day span between themNOAA 1991–2020 Climate Normals
- 108 documented contamination sites on the federal record near Onamia, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Onamia's boundary and the 628 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~162-day seasonGrowable Ground crop-matching engine
- The ecoregion at Onamia's own centroid, the Northern Lakes and ForestsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Onamia's 628 acres read through its county's SSURGO summaryfrom Mille Lacs County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Mille Lacs 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 Mille Lacs County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Onamia's 628 acreswhy one lot differs from the next →
- Which side of Onamia you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 628 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Onamia-wide figureread your own land →
More in Minnesota
Wider growing context
What grows across MinnesotaOnamia sits outside our named growing regions, so Minnesota as a whole is its closest context here.