Barnum, Iowa, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Barnum, 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 Barnum 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 Barnum — soil, climate, flood, and parcel records. How we handle your address.
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Barnum — the short answer
Barnum, Iowa: USDA zone 5a, about 189 days between hard freezes, across 239 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 16
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~189
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 239 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 Barnum's average, not your lot's — a low corner or a tree line moves it. Against Barnum's 189-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Barnum
Each reading below is measured for Barnum itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredBarnum 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
MeasuredBarnum 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 Barnum is in
Barnum sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Barnum's own centroid rather than borrowed from Webster County.
What Grows in Barnum
Every plant below cleared Barnum's own zone 5a and its 189-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Barnum?
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 19; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 16 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 22 — 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 Barnum
Closest first, within ~10 miles of Barnum. Listing isn't leaking, and distance isn't exposure.
- BYSONS COUNTRY STOREUnderground Storage Tanks · 900 ft
- 089N30W23CBC 14551 1964Barnum 1Nitrate · 1000 ft
- NORTHWEST WEBSTER SCHOOLUnderground Storage Tanks · 1100 ft
- VAN DIEST SUPPLY COMPANYToxics Release Inventory · 2200 ft
- 089N30W11DDA 02398 1946Nitrate · 2.1 mi
- LIZARD CREEK FISH KILLSuperfund · 2.7 mi
- CARGILL, INC. - FORT DODGEToxics Release Inventory · 2.7 mi
- CARGILL, INC. - FORT DODGEBrownfields · 2.7 mi
- 089N30W02DCD 02218 1946Nitrate · 2.8 mi
- CJ BIO AMERICAToxics Release Inventory · 2.8 mi
- CJ BIO AMERICABrownfields · 2.8 mi
- 089N29W31BDA 03442 1948Nitrate · 3.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Barnum'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 Barnum.
Total Sites
251
within ~10 miles of Barnum
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Barnum
Severity Distribution
within ~10 miles of Barnum
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
Check your specific parcel in Barnum
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 Barnum average
Your land is one point inside Barnum
Everything above resolves to Barnum as a whole — one PHZM band and one 28°F frost record, read across 239 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 Barnum Average
Barnum Average
- ●USDA Zones 5a, averaged across Barnum
- ●One soil character for all of Barnum
- ●Frost dates read at Barnum's scale: Apr 16 to Oct 22
YOUR Parcel
- ✓Your exact zone, not Barnum's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Barnum
Pull a site-specific report for your exact address in Barnum, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Barnum averages can't show:
We read public map data around Barnum — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Barnum average
How we know this about Barnum
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 Barnum’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 Barnum
When does frost risk typically end in Barnum?
The last hard freeze (28°F) in Barnum typically lands around Apr 16, 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 7.
When is the first frost in Barnum?
The first hard freeze (28°F) in Barnum typically arrives around Oct 22, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 8, so the watching starts about Sep 22 — about 189 days after the spring freeze cleared.
How long is the growing season in Barnum?
Measured between 28°F hard freezes, Barnum sees about 189 frost-free days — roughly Apr 16 through Oct 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 7 to Oct 8, about 154 days.
Is the soil safe to grow vegetables in Barnum?
The federal record around Barnum is a meaningful one — 251 documented sites, mostly Underground Storage Tanks entries (139), the nearest Underground Storage Tanks record about 0.2 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 Barnum?
From about Sep 22 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 22 (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 22. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Barnum's scale — its 5a band and its 189-day season. Your yard writes its own version of Barnum'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 Barnum’s own scale
6 of the readings below were taken at Barnum's own scale — its own ~189-day season between 28°F freezes, the 239 acres it covers and 251 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Barnum's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Barnum's own 28°F hard-freeze dates, about Apr 16 and Oct 22 and the ~189-day span between themNOAA 1991–2020 Climate Normals
- 251 documented contamination sites on the federal record near Barnum, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Barnum's boundary and the 239 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~189-day seasonGrowable Ground crop-matching engine
- The ecoregion at Barnum'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 Barnum's 239 acres read through its county's SSURGO summaryfrom Webster County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Webster 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 Webster County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Barnum's 239 acreswhy one lot differs from the next →
- Which side of Barnum you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 239 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 Barnum-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaBarnum sits outside our named growing regions, so Iowa as a whole is its closest context here.