Oskaloosa, Iowa, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Oskaloosa, 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 Oskaloosa 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 Oskaloosa — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Oskaloosa — the short answer
Oskaloosa, Iowa: USDA zone 5b, about 199 days between hard freezes, across 5K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 25
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~199
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 5K 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 5b is Oskaloosa's average, not your lot's — a low corner or a tree line moves it. Against Oskaloosa's 199-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Oskaloosa
Each reading below is measured for Oskaloosa itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOskaloosa runs about 199 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
MeasuredOskaloosa sits in USDA hardiness zone 5b.
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 Oskaloosa is in
Oskaloosa sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Oskaloosa's own centroid rather than borrowed from Mahaska County.
What Grows in Oskaloosa
Every plant below cleared Oskaloosa's own zone 5b and its 199-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Oskaloosa?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 25 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Oskaloosa
Closest first, within ~10 miles of Oskaloosa. Listing isn't leaking, and distance isn't exposure.
- VAN HULZEN OIL COUnderground Storage Tanks · 850 ft
- CRYSTAL CLEANERSUnderground Storage Tanks · 1200 ft
- JIFFY CONVENIENCE STOREUnderground Storage Tanks · 1500 ft
- JERRYS AUTOMOTIVEBrownfields · 1500 ft
- FORMER AMOCO #5953Underground Storage Tanks · 1600 ft
- GOODYEAR AUTO-MAHASKA COUNTY TIREBrownfields · 1600 ft
- OSKALOOSA GAS AND OILUnderground Storage Tanks · 1600 ft
- MUSCO SPORTS LIGHTING LLCBrownfields · 1700 ft
- ELECTRIC MOTOR SERVICEBrownfields · 1700 ft
- SHERWIN-WILLIAMS 703848Brownfields · 1800 ft
- PENN CENTRAL MALLUnderground Storage Tanks · 1800 ft
- OSKALOOSA FOOD PRODUCTSToxics Release Inventory · 2000 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Oskaloosa'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 Oskaloosa.
Total Sites
213
within ~10 miles of Oskaloosa
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Oskaloosa
Severity Distribution
within ~10 miles of Oskaloosa
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Oskaloosa, Nitrate runs higher than the national average — 68 sites within ~10 miles of Oskaloosa. 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 Oskaloosa
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 Oskaloosa average
Your land is one point inside Oskaloosa
Everything above resolves to Oskaloosa as a whole — one PHZM band and one 28°F frost record, read across 5K 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 Oskaloosa Average
Oskaloosa Average
- ●USDA Zones 5b, averaged across Oskaloosa
- ●One soil character for all of Oskaloosa
- ●Frost dates read at Oskaloosa's scale: Apr 9 to Oct 25
YOUR Parcel
- ✓Your exact zone, not Oskaloosa's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Oskaloosa
Pull a site-specific report for your exact address in Oskaloosa, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Oskaloosa averages can't show:
We read public map data around Oskaloosa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Oskaloosa average
How we know this about Oskaloosa
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 Oskaloosa’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 Oskaloosa
When does frost risk typically end in Oskaloosa?
The last hard freeze (28°F) in Oskaloosa typically lands around Apr 9, 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 Apr 30.
When is the first frost in Oskaloosa?
The first hard freeze (28°F) in Oskaloosa typically arrives around Oct 25, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 11, so the watching starts about Sep 25 — about 199 days after the spring freeze cleared.
How long is the growing season in Oskaloosa?
Measured between 28°F hard freezes, Oskaloosa sees about 199 frost-free days — roughly Apr 9 through Oct 25, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 30 to Oct 11, about 164 days.
Is the soil safe to grow vegetables in Oskaloosa?
The federal record around Oskaloosa is a meaningful one — 213 documented sites, mostly Underground Storage Tanks entries (86), the nearest Underground Storage Tanks record about 0.2 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.
How do I protect my plants from frost in Oskaloosa?
From about Sep 25 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 25 (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 25. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Oskaloosa's scale — its 5b band and its 199-day season. Your yard writes its own version of Oskaloosa'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 Oskaloosa’s own scale
6 of the readings below were taken at Oskaloosa's own scale — its own ~199-day season between 28°F freezes, the 5,157 acres it covers and 213 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Oskaloosa's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Oskaloosa's own 28°F hard-freeze dates, about Apr 9 and Oct 25 and the ~199-day span between themNOAA 1991–2020 Climate Normals
- 213 documented contamination sites on the federal record near Oskaloosa, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Oskaloosa's boundary and the 5,157 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~199-day seasonGrowable Ground crop-matching engine
- The ecoregion at Oskaloosa's own centroid, the Western Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Oskaloosa's 5,157 acres read through its county's SSURGO summaryfrom Mahaska County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Mahaska County
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Mahaska County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Oskaloosa's 5,157 acreswhy one lot differs from the next →
- Which side of Oskaloosa you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,157 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 miles 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 Oskaloosa-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaOskaloosa sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides