Dunkerton, Iowa, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Dunkerton, 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 Dunkerton 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 Dunkerton — soil, climate, flood, and parcel records. How we handle your address.
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Dunkerton — the short answer
Dunkerton, Iowa: USDA zone 5a, about 184 days between hard freezes, across 766 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~184
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 766 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 Dunkerton's average, not your lot's — a low corner or a tree line moves it. Against Dunkerton's 184-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Dunkerton
Each reading below is measured for Dunkerton itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDunkerton runs about 184 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
MeasuredDunkerton 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 Dunkerton is in
Dunkerton sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Dunkerton's own centroid rather than borrowed from Black Hawk County.
What Grows in Dunkerton
Every plant below cleared Dunkerton's own zone 5a and its 184-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Dunkerton?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 18 — 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 Dunkerton
Closest first, within ~10 miles of Dunkerton. Listing isn't leaking, and distance isn't exposure.
- 090N11W33BCB 01287 1940Dunkerton 1Nitrate · 300 ft
- DUNKERTON COMMUNTIY SCHOOLSUnderground Storage Tanks · 550 ft
- KWIK STAR #702Underground Storage Tanks · 1400 ft
- BLACK HAWK COUNTY SHOPUnderground Storage Tanks · 1700 ft
- HAUPTLY CONSTRUCTION & EQUIP COUnderground Storage Tanks · 1700 ft
- DUNKERTON COOP ELEVATORUnderground Storage Tanks · 2100 ft
- Not KnownUnderground Storage Tanks · 2300 ft
- FORMERLY DEWAR HARDWAREUnderground Storage Tanks · 4.3 mi
- 089N11W13CAC 1978Nitrate · 4.9 mi
- WILLARD FROST FARMToxics Release Inventory · 5.0 mi
- EAGLE OTTAWA LLCToxics Release Inventory · 5.9 mi
- EAGLE OTTAWA LLCBrownfields · 5.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dunkerton'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 Dunkerton.
Sources Checked
within ~10 miles of Dunkerton
Severity Distribution
within ~10 miles of Dunkerton
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dunkerton, Toxics Release Inventory runs higher than the national average — 14 sites within ~10 miles of Dunkerton. 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.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Dunkerton
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 Dunkerton average
Your land is one point inside Dunkerton
Everything above resolves to Dunkerton as a whole — one PHZM band and one 28°F frost record, read across 766 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 Dunkerton Average
Dunkerton Average
- ●USDA Zones 5a, averaged across Dunkerton
- ●One soil character for all of Dunkerton
- ●Frost dates read at Dunkerton's scale: Apr 17 to Oct 18
YOUR Parcel
- ✓Your exact zone, not Dunkerton's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Dunkerton
Pull a site-specific report for your exact address in Dunkerton, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dunkerton averages can't show:
We read public map data around Dunkerton — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dunkerton average
How we know this about Dunkerton
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 Dunkerton’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 Dunkerton
When does frost risk typically end in Dunkerton?
The last hard freeze (28°F) in Dunkerton typically lands around Apr 17, 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 8.
When is the first frost in Dunkerton?
The first hard freeze (28°F) in Dunkerton typically arrives around Oct 18, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 4, so the watching starts about Sep 18 — about 184 days after the spring freeze cleared.
How long is the growing season in Dunkerton?
Measured between 28°F hard freezes, Dunkerton sees about 184 frost-free days — roughly Apr 17 through Oct 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 8 to Oct 4, about 149 days.
Is the soil safe to grow vegetables in Dunkerton?
The federal record around Dunkerton is a meaningful one — 213 documented sites, mostly Underground Storage Tanks entries (109), the nearest Nitrate 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 Dunkerton?
From about Sep 18 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 18 (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 18. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Dunkerton's scale — its 5a band and its 184-day season. Your yard writes its own version of Dunkerton'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 Dunkerton’s own scale
6 of the readings below were taken at Dunkerton's own scale — its own ~184-day season between 28°F freezes, the 766 acres it covers and 213 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Dunkerton's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Dunkerton's own 28°F hard-freeze dates, about Apr 17 and Oct 18 and the ~184-day span between themNOAA 1991–2020 Climate Normals
- 213 documented contamination sites on the federal record near Dunkerton, the closest Nitrate record under a tenth of a mile out from the town centreFederal environmental registers
- Dunkerton's boundary and the 766 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~184-day seasonGrowable Ground crop-matching engine
- The ecoregion at Dunkerton'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 Dunkerton's 766 acres read through its county's SSURGO summaryfrom Black Hawk County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Black Hawk 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 Black Hawk County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Dunkerton's 766 acreswhy one lot differs from the next →
- Which side of Dunkerton you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 766 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate 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 Dunkerton-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaDunkerton sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides