Owasa, Iowa, sits in USDA hardiness zone 5a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Owasa, 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 Owasa 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 Owasa — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Owasa — the short answer
Owasa, Iowa: USDA zone 5a, about 187 days between hard freezes, across 360 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~187
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 360 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 Owasa's average, not your lot's — a low corner or a tree line moves it. Against Owasa's 187-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Owasa
Each reading below is measured for Owasa itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOwasa runs about 187 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
MeasuredOwasa 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 Owasa is in
Owasa sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Owasa's own centroid rather than borrowed from Hardin County.
What Grows in Owasa
Every plant below cleared Owasa's own zone 5a and its 187-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Owasa?
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 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 19 — 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 Owasa
Closest first, within ~10 miles of Owasa. Listing isn't leaking, and distance isn't exposure.
- OWASA COOPERATIVE ELEV COUnderground Storage Tanks · 600 ft
- GASOLINE ALLEYUnderground Storage Tanks · 650 ft
- PRESTON AUSTUnderground Storage Tanks · 1.6 mi
- RURAL IOWA LANDFILLUnderground Storage Tanks · 3.3 mi
- IOWA FALLS MUNICIPAL AIRPORTUnderground Storage Tanks · 3.9 mi
- WALMART SUPERCENTER #1546Brownfields · 5.7 mi
- MIDLAND POWER COOPERATIVEUnderground Storage Tanks · 5.8 mi
- HANDI STOP 66Underground Storage Tanks · 5.8 mi
- 089N20W19CBB 01720 1943Nitrate · 5.9 mi
- ANIMAL HEALTH INTERNATIONALBrownfields · 5.9 mi
- KWIK STAR 103Underground Storage Tanks · 5.9 mi
- TIMES CITIZENBrownfields · 5.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Owasa'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 Owasa.
Total Sites
304
within ~10 miles of Owasa
Risk Level
Elevated
Highest-severity
11 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Owasa
Severity Distribution
within ~10 miles of Owasa
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Owasa, Nitrate runs higher than the national average — 168 sites within ~10 miles of Owasa. 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 Owasa
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 Owasa average
Your land is one point inside Owasa
Everything above resolves to Owasa as a whole — one PHZM band and one 28°F frost record, read across 360 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 Owasa Average
Owasa Average
- ●USDA Zones 5a, averaged across Owasa
- ●One soil character for all of Owasa
- ●Frost dates read at Owasa's scale: Apr 15 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Owasa's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Owasa
Pull a site-specific report for your exact address in Owasa, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Owasa averages can't show:
We read public map data around Owasa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Owasa average
How we know this about Owasa
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 Owasa’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 Owasa
When does frost risk typically end in Owasa?
The last hard freeze (28°F) in Owasa typically lands around Apr 15, 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 6.
When is the first frost in Owasa?
The first hard freeze (28°F) in Owasa typically arrives around Oct 19, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 5, so the watching starts about Sep 19 — about 187 days after the spring freeze cleared.
How long is the growing season in Owasa?
Measured between 28°F hard freezes, Owasa sees about 187 frost-free days — roughly Apr 15 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 6 to Oct 5, about 152 days.
Is the soil safe to grow vegetables in Owasa?
The federal record around Owasa is a meaningful one — 304 documented sites, mostly Nitrate entries (168), the nearest Underground Storage Tanks record about 0.1 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 Owasa?
From about Sep 19 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 19 (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 19. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Owasa's scale — its 5a band and its 187-day season. Your yard writes its own version of Owasa'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 Owasa’s own scale
6 of the readings below were taken at Owasa's own scale — its own ~187-day season between 28°F freezes, the 360 acres it covers and 304 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Owasa's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Owasa's own 28°F hard-freeze dates, about Apr 15 and Oct 19 and the ~187-day span between themNOAA 1991–2020 Climate Normals
- 304 documented contamination sites on the federal record near Owasa, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Owasa's boundary and the 360 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~187-day seasonGrowable Ground crop-matching engine
- The ecoregion at Owasa'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 Owasa's 360 acres read through its county's SSURGO summaryfrom Hardin County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Hardin 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 Hardin County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Owasa's 360 acreswhy one lot differs from the next →
- Which side of Owasa you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 360 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 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 Owasa-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaOwasa sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides