Dunlap, Iowa, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
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 Dunlap, 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 Dunlap 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 Dunlap — soil, climate, flood, and parcel records. How we handle your address.
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Dunlap — the short answer
Dunlap, Iowa: USDA zone 5b, about 189 days between hard freezes, across 799 acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 13
- 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
- ~189
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 799 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 Dunlap's average, not your lot's — a low corner or a tree line moves it. Against Dunlap's 189-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Dunlap
Each reading below is measured for Dunlap itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDunlap runs about 189 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
MeasuredDunlap 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 Dunlap is in
Dunlap sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Dunlap's own centroid rather than borrowed from Harrison County.
What Grows in Dunlap
Every plant below cleared Dunlap's own zone 5b and its 189-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Dunlap?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 13 (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. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Dunlap
Closest first, within ~10 miles of Dunlap. Listing isn't leaking, and distance isn't exposure.
- RICHS MINI MARTUnderground Storage Tanks · 400 ft
- DUNLAP FARMERS COOPUnderground Storage Tanks · 1000 ft
- COZY CORNERUnderground Storage Tanks · 1100 ft
- Not KnownUnderground Storage Tanks · 1200 ft
- DUNLAP COMM. SCHOOLSUnderground Storage Tanks · 1300 ft
- HARRISON COUNTY SHOPUnderground Storage Tanks · 1300 ft
- 081N41W03DBBD 1925Dunlap 1Nitrate · 1300 ft
- 081N41W03DBBD 1954Dunlap 2Nitrate · 1400 ft
- DUNLAP OIL COUnderground Storage Tanks · 1700 ft
- THE TOWN AND COUNTRY STOREUnderground Storage Tanks · 1800 ft
- QUALITY LIQUID FEEDS INCToxics Release Inventory · 1900 ft
- HELLER IMPLEMENT INCUnderground Storage Tanks · 2000 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Dunlap'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 Dunlap.
Total Sites
75
within ~10 miles of Dunlap
Risk Level
Moderate
Highest-severity
2 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Dunlap
Severity Distribution
within ~10 miles of Dunlap
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dunlap, Nitrate runs higher than the national average — 38 sites within ~10 miles of Dunlap. 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 Dunlap
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 Dunlap average
Your land is one point inside Dunlap
Everything above resolves to Dunlap as a whole — one PHZM band and one 28°F frost record, read across 799 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 Dunlap Average
Dunlap Average
- ●USDA Zones 5b, averaged across Dunlap
- ●One soil character for all of Dunlap
- ●Frost dates read at Dunlap's scale: Apr 13 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Dunlap's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Dunlap
Pull a site-specific report for your exact address in Dunlap, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dunlap averages can't show:
We read public map data around Dunlap — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dunlap average
How we know this about Dunlap
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 Dunlap’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 Dunlap
When does frost risk typically end in Dunlap?
The last hard freeze (28°F) in Dunlap typically lands around Apr 13, 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 4.
When is the first frost in Dunlap?
The first hard freeze (28°F) in Dunlap 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 189 days after the spring freeze cleared.
How long is the growing season in Dunlap?
Measured between 28°F hard freezes, Dunlap sees about 189 frost-free days — roughly Apr 13 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 4 to Oct 5, about 154 days.
Is the soil safe to grow vegetables in Dunlap?
The federal record around Dunlap shows 75 documented sites, mostly Nitrate entries (38), the nearest Underground Storage Tanks record under a tenth of a mile 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 Dunlap?
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 Dunlap's scale — its 5b band and its 189-day season. Your yard writes its own version of Dunlap'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 Dunlap’s own scale
6 of the readings below were taken at Dunlap's own scale — its own ~189-day season between 28°F freezes, the 799 acres it covers and 75 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Dunlap's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Dunlap's own 28°F hard-freeze dates, about Apr 13 and Oct 19 and the ~189-day span between themNOAA 1991–2020 Climate Normals
- 75 documented contamination sites on the federal record near Dunlap, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Dunlap's boundary and the 799 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~189-day seasonGrowable Ground crop-matching engine
- The ecoregion at Dunlap'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 Dunlap's 799 acres read through its county's SSURGO summaryfrom Harrison County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Harrison 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 Harrison County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Dunlap's 799 acreswhy one lot differs from the next →
- Which side of Dunlap you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 799 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 Dunlap-wide figureread your own land →
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