Ottumwa, Iowa, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
The conditions favor cabbage, blueberry, lavender, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Ottumwa, 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 Ottumwa 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 Ottumwa — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Ottumwa — the short answer
Ottumwa, Iowa: USDA zone 5b, about 205 days between hard freezes, across 10K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~205
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 10K 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 Ottumwa's average, not your lot's — a low corner or a tree line moves it. Against Ottumwa's 205-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Ottumwa
Each reading below is measured for Ottumwa itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOttumwa runs about 205 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredOttumwa 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 Ottumwa is in
Ottumwa sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. That is read at Ottumwa's own centroid rather than borrowed from Wapello County.
What Grows in Ottumwa
Every plant below cleared Ottumwa's own zone 5b and its 205-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Ottumwa?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 9; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 6 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 28 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
What's on the federal record near Ottumwa
Closest first, within ~10 miles of Ottumwa. Listing isn't leaking, and distance isn't exposure.
- CENTRAL STATES COCA-COLAUnderground Storage Tanks · 450 ft
- TCI-WESTMARCUnderground Storage Tanks · 700 ft
- IOWA SOUTHERN UTILITIES COMPANYUnderground Storage Tanks · 850 ft
- HAW HARDWAREUnderground Storage Tanks · 900 ft
- VOSS EQUIP RENTAL CO INCUnderground Storage Tanks · 950 ft
- CONTINENTAL BAKING COUnderground Storage Tanks · 1000 ft
- UNITED PARCEL SERVICEUnderground Storage Tanks · 1100 ft
- UNITED PARCEL SERVICEBrownfields · 1200 ft
- BETTY JANE & W REG WELLMANUnderground Storage Tanks · 1200 ft
- CITY OF OTTUMWA GARAGEUnderground Storage Tanks · 1400 ft
- OTTUMWA, CITY OF - TRAFFIC DEPTBrownfields · 1400 ft
- US POSTAL SERVICEUnderground Storage Tanks · 1400 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Ottumwa'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 Ottumwa.
Sources Checked
within ~10 miles of Ottumwa
Severity Distribution
within ~10 miles of Ottumwa
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Ottumwa, two things run higher than the national average within ~10 miles of Ottumwa — Toxics Release Inventory (16 sites) and Superfund (3 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Ottumwa
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 Ottumwa average
Your land is one point inside Ottumwa
Everything above resolves to Ottumwa as a whole — one PHZM band and one 28°F frost record, read across 10K 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 Ottumwa Average
Ottumwa Average
- ●USDA Zones 5b, averaged across Ottumwa
- ●One soil character for all of Ottumwa
- ●Frost dates read at Ottumwa's scale: Apr 6 to Oct 28
YOUR Parcel
- ✓Your exact zone, not Ottumwa's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Ottumwa
Pull a site-specific report for your exact address in Ottumwa, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Ottumwa averages can't show:
We read public map data around Ottumwa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Ottumwa average
How we know this about Ottumwa
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 Ottumwa’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 Ottumwa
When does frost risk typically end in Ottumwa?
The last hard freeze (28°F) in Ottumwa typically lands around Apr 6, 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 27.
When is the first frost in Ottumwa?
The first hard freeze (28°F) in Ottumwa typically arrives around Oct 28, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 14, so the watching starts about Sep 28 — about 205 days after the spring freeze cleared.
How long is the growing season in Ottumwa?
Measured between 28°F hard freezes, Ottumwa sees about 205 frost-free days — roughly Apr 6 through Oct 28, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 27 to Oct 14, about 170 days.
Is the soil safe to grow vegetables in Ottumwa?
The federal record around Ottumwa is a meaningful one — 241 documented sites, mostly Underground Storage Tanks entries (121), the nearest Underground Storage Tanks record under a tenth of a mile 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 Ottumwa?
From about Sep 28 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 28 (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 28. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Ottumwa's scale — its 5b band and its 205-day season. Your yard writes its own version of Ottumwa'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 Ottumwa’s own scale
6 of the readings below were taken at Ottumwa's own scale — its own ~205-day season between 28°F freezes, the 10,281 acres it covers and 241 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Ottumwa's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Ottumwa's own 28°F hard-freeze dates, about Apr 6 and Oct 28 and the ~205-day span between themNOAA 1991–2020 Climate Normals
- 241 documented contamination sites on the federal record near Ottumwa, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Ottumwa's boundary and the 10,281 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~205-day seasonGrowable Ground crop-matching engine
- The ecoregion at Ottumwa's own centroid, the Central Irregular PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Ottumwa's 10,281 acres read through its county's SSURGO summaryfrom Wapello County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Wapello 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 Wapello County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Ottumwa's 10,281 acreswhy one lot differs from the next →
- Which side of Ottumwa you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 10,281 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 Ottumwa-wide figureread your own land →