Oto, Iowa, sits in USDA hardiness zone 5a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Crops well matched to these conditions include cabbage, cranberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Oto, 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 Oto 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 Oto — soil, climate, flood, and parcel records. How we handle your address.
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Oto — the short answer
Oto, Iowa: USDA zone 5a, about 182 days between hard freezes, across 172 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~182
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 172 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 5a is Oto's average, not your lot's — a low corner or a tree line moves it. Against Oto's 182-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Oto
Each reading below is measured for Oto itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOto runs about 182 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
MeasuredOto sits in USDA hardiness zone 5a.
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 Oto is in
Oto sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Oto's own centroid rather than borrowed from Woodbury County.
What Grows in Oto
Every plant below cleared Oto's own zone 5a and its 182-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Oto?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 17 — 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 Oto
Closest first, within ~10 miles of Oto. Listing isn't leaking, and distance isn't exposure.
- WOODBURY COUNTY HIGHWAY DEPTUnderground Storage Tanks · 1100 ft
- WOODBURY COUNTY MAINTENANCE GARAGEUnderground Storage Tanks · 1200 ft
- DIOSYNTH INCUnderground Storage Tanks · 1300 ft
- OTO SINCLAIRUnderground Storage Tanks · 1500 ft
- 31 QUICK STOPUnderground Storage Tanks · 1900 ft
- 086N44W26DBBB 17453 1964Smithland 2Nitrate · 3.9 mi
- 086N44W26DBBB 1933SmithlandNitrate · 3.9 mi
- 086N44W26DBCA 05939 1952Smithland 1Nitrate · 4.0 mi
- SMITHLAND COUNTRY STOREUnderground Storage Tanks · 4.1 mi
- SOUTHWOOD CONSERVATION AREAUnderground Storage Tanks · 4.1 mi
- Not KnownUnderground Storage Tanks · 4.1 mi
- BOBS SERVICEUnderground Storage Tanks · 4.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Oto'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 Oto.
Severity Distribution
within ~10 miles of Oto
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Oto, Nitrate runs higher than the national average — 32 sites within ~10 miles of Oto. 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 Oto
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 Oto average
Your land is one point inside Oto
Everything above resolves to Oto as a whole — one PHZM band and one 28°F frost record, read across 172 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 Oto Average
Oto Average
- ●USDA Zones 5a, averaged across Oto
- ●One soil character for all of Oto
- ●Frost dates read at Oto's scale: Apr 18 to Oct 17
YOUR Parcel
- ✓Your exact zone, not Oto's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Oto
Pull a site-specific report for your exact address in Oto, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Oto averages can't show:
We read public map data around Oto — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Oto average
How we know this about Oto
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 Oto’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 Oto
When does frost risk typically end in Oto?
The last hard freeze (28°F) in Oto typically lands around Apr 18, 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 9.
When is the first frost in Oto?
The first hard freeze (28°F) in Oto typically arrives around Oct 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 3, so the watching starts about Sep 17 — about 182 days after the spring freeze cleared.
How long is the growing season in Oto?
Measured between 28°F hard freezes, Oto sees about 182 frost-free days — roughly Apr 18 through Oct 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 3, about 147 days.
Is the soil safe to grow vegetables in Oto?
The federal record around Oto shows 75 documented sites, mostly Underground Storage Tanks entries (36), the nearest Underground Storage Tanks record about 0.2 miles 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 Oto?
From about Sep 17 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 17 (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 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Oto's scale — its 5a band and its 182-day season. Your yard writes its own version of Oto'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 Oto’s own scale
6 of the readings below were taken at Oto's own scale — its own ~182-day season between 28°F freezes, the 172 acres it covers and 75 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Oto's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Oto's own 28°F hard-freeze dates, about Apr 18 and Oct 17 and the ~182-day span between themNOAA 1991–2020 Climate Normals
- 75 documented contamination sites on the federal record near Oto, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Oto's boundary and the 172 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~182-day seasonGrowable Ground crop-matching engine
- The ecoregion at Oto'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 Oto's 172 acres read through its county's SSURGO summaryfrom Woodbury County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Woodbury 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 Woodbury County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Oto's 172 acreswhy one lot differs from the next →
- Which side of Oto you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 172 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 Oto-wide figureread your own land →
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