Red Oak, Iowa, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
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 Red Oak, 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 Red Oak 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 Red Oak — soil, climate, flood, and parcel records. How we handle your address.
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Red Oak — the short answer
Red Oak, Iowa: USDA zone 5b, about 196 days between hard freezes, across 3K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 23
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~196
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 3K 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 Red Oak's average, not your lot's — a low corner or a tree line moves it. Against Red Oak's 196-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Red Oak
Each reading below is measured for Red Oak itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredRed Oak runs about 196 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
MeasuredRed Oak 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 Red Oak is in
Red Oak sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Red Oak's own centroid rather than borrowed from Montgomery County.
What Grows in Red Oak
Every plant below cleared Red Oak's own zone 5b and its 196-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Red Oak?
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 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 23 — 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 Red Oak
Closest first, within ~10 miles of Red Oak. Listing isn't leaking, and distance isn't exposure.
- AT&T COMM - RED OAKUnderground Storage Tanks · 1000 ft
- RED OAK SHELLUnderground Storage Tanks · 1300 ft
- FINEST CLEANERSBrownfields · 1800 ft
- RED OAK CEMETERYUnderground Storage Tanks · 2100 ft
- R K BELT & SONS INCUnderground Storage Tanks · 2100 ft
- MONTGOMERY COUNTY MEMORIAL HOSPITALUnderground Storage Tanks · 2300 ft
- FORMER WARIN OIL COMPANYUnderground Storage Tanks · 2300 ft
- HARDY FENCING & CONCRETEUnderground Storage Tanks · 2300 ft
- FORMER SERVICE STATION #9648Underground Storage Tanks · 2300 ft
- COASTAL MART #1807Underground Storage Tanks · 2300 ft
- FALKS ICE CREAMUnderground Storage Tanks · 2400 ft
- CASEY''S GENERAL STORE 1728Underground Storage Tanks · 2400 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Red Oak'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 Red Oak.
Sources Checked
within ~10 miles of Red Oak
Severity Distribution
within ~10 miles of Red Oak
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Red Oak, two things run higher than the national average within ~10 miles of Red Oak — Superfund (3 sites) and Toxics Release Inventory (13 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Red Oak
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 Red Oak average
Your land is one point inside Red Oak
Everything above resolves to Red Oak as a whole — one PHZM band and one 28°F frost record, read across 3K 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 Red Oak Average
Red Oak Average
- ●USDA Zones 5b, averaged across Red Oak
- ●One soil character for all of Red Oak
- ●Frost dates read at Red Oak's scale: Apr 10 to Oct 23
YOUR Parcel
- ✓Your exact zone, not Red Oak's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Red Oak
Pull a site-specific report for your exact address in Red Oak, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Red Oak averages can't show:
We read public map data around Red Oak — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Red Oak average
How we know this about Red Oak
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 Red Oak’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 Red Oak
When does frost risk typically end in Red Oak?
The last hard freeze (28°F) in Red Oak typically lands around Apr 10, 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 1.
When is the first frost in Red Oak?
The first hard freeze (28°F) in Red Oak typically arrives around Oct 23, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 9, so the watching starts about Sep 23 — about 196 days after the spring freeze cleared.
How long is the growing season in Red Oak?
Measured between 28°F hard freezes, Red Oak sees about 196 frost-free days — roughly Apr 10 through Oct 23, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 1 to Oct 9, about 161 days.
Is the soil safe to grow vegetables in Red Oak?
The federal record around Red Oak is a meaningful one — 124 documented sites, mostly Underground Storage Tanks entries (50), 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 Red Oak?
From about Sep 23 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 23 (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 23. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Red Oak's scale — its 5b band and its 196-day season. Your yard writes its own version of Red Oak'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 Red Oak’s own scale
6 of the readings below were taken at Red Oak's own scale — its own ~196-day season between 28°F freezes, the 2,513 acres it covers and 124 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Red Oak's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Red Oak's own 28°F hard-freeze dates, about Apr 10 and Oct 23 and the ~196-day span between themNOAA 1991–2020 Climate Normals
- 124 documented contamination sites on the federal record near Red Oak, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Red Oak's boundary and the 2,513 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~196-day seasonGrowable Ground crop-matching engine
- The ecoregion at Red Oak'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 Red Oak's 2,513 acres read through its county's SSURGO summaryfrom Montgomery County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Montgomery 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 Montgomery County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Red Oak's 2,513 acreswhy one lot differs from the next →
- Which side of Red Oak you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,513 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 Red Oak-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaRed Oak sits outside our named growing regions, so Iowa as a whole is its closest context here.