Decatur, Iowa, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Reliable performers under these conditions include cabbage, cranberry, lavender, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Decatur, 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 Decatur 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 Decatur — soil, climate, flood, and parcel records. How we handle your address.
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Decatur — the short answer
Decatur, Iowa: USDA zone 5b, about 198 days between hard freezes, across 242 acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 24
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~198
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 242 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 Decatur's average, not your lot's — a low corner or a tree line moves it. Against Decatur's 198-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Decatur
Each reading below is measured for Decatur itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDecatur runs about 198 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
MeasuredDecatur 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 Decatur is in
Decatur sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. That is read at Decatur's own centroid rather than borrowed from Decatur County.
What Grows in Decatur
Every plant below cleared Decatur's own zone 5b and its 198-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Decatur?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 24 — 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 Decatur
Closest first, within ~10 miles of Decatur. Listing isn't leaking, and distance isn't exposure.
- M & M WELDINGBrownfields · 450 ft
- ABANDONED GAS STATIONUnderground Storage Tanks · 450 ft
- DECATUR QUARRYUnderground Storage Tanks · 450 ft
- SMITH OIL COUnderground Storage Tanks · 1400 ft
- FORMER ONE STOP C-STOREUnderground Storage Tanks · 1400 ft
- DECATUR CITY TEXACOUnderground Storage Tanks · 0.6 mi
- IDOTUnderground Storage Tanks · 3.8 mi
- IOWA DEPARTMENT OF TRANSPORTATIONBrownfields · 3.8 mi
- COASTAL MART #1025Underground Storage Tanks · 3.9 mi
- ITC TRANSMISSION - MIDWEST LEONBrownfields · 4.3 mi
- 069N25W29DDDC 14387 1963Leon 4Nitrate · 4.4 mi
- CENT DECATUR COMM SCH BUS BARNUnderground Storage Tanks · 4.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Decatur'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 Decatur.
Sources Checked
within ~10 miles of Decatur
Severity Distribution
within ~10 miles of Decatur
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Decatur, Underground Storage Tanks runs higher than the national average — 46 sites within ~10 miles of Decatur. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Decatur
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 Decatur average
Your land is one point inside Decatur
Everything above resolves to Decatur as a whole — one PHZM band and one 28°F frost record, read across 242 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 Decatur Average
Decatur Average
- ●USDA Zones 5b, averaged across Decatur
- ●One soil character for all of Decatur
- ●Frost dates read at Decatur's scale: Apr 9 to Oct 24
YOUR Parcel
- ✓Your exact zone, not Decatur's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Decatur
Pull a site-specific report for your exact address in Decatur, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Decatur averages can't show:
We read public map data around Decatur — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Decatur average
How we know this about Decatur
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 Decatur’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 Decatur
When does frost risk typically end in Decatur?
The last hard freeze (28°F) in Decatur typically lands around Apr 9, 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 30.
When is the first frost in Decatur?
The first hard freeze (28°F) in Decatur typically arrives around Oct 24, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 10, so the watching starts about Sep 24 — about 198 days after the spring freeze cleared.
How long is the growing season in Decatur?
Measured between 28°F hard freezes, Decatur sees about 198 frost-free days — roughly Apr 9 through Oct 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 30 to Oct 10, about 163 days.
Is the soil safe to grow vegetables in Decatur?
The federal record around Decatur shows 68 documented sites, mostly Underground Storage Tanks entries (46), the nearest Brownfields 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 Decatur?
From about Sep 24 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 24 (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 24. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Decatur's scale — its 5b band and its 198-day season. Your yard writes its own version of Decatur'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 Decatur’s own scale
6 of the readings below were taken at Decatur's own scale — its own ~198-day season between 28°F freezes, the 242 acres it covers and 68 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Decatur's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Decatur's own 28°F hard-freeze dates, about Apr 9 and Oct 24 and the ~198-day span between themNOAA 1991–2020 Climate Normals
- 68 documented contamination sites on the federal record near Decatur, the closest Brownfields record under a tenth of a mile out from the town centreFederal environmental registers
- Decatur's boundary and the 242 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~198-day seasonGrowable Ground crop-matching engine
- The ecoregion at Decatur's own centroid, the Central Irregular PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Decatur's 242 acres read through its county's SSURGO summaryfrom Decatur County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Decatur 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 Decatur County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Decatur's 242 acreswhy one lot differs from the next →
- Which side of Decatur you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 242 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields 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 Decatur-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaDecatur sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides