Garnavillo, Iowa, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
The conditions favor cabbage, cranberry, lavender, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Garnavillo, 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 Garnavillo 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 Garnavillo — soil, climate, flood, and parcel records. How we handle your address.
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Garnavillo — the short answer
Garnavillo, Iowa: USDA zone 5a, about 186 days between hard freezes, across 604 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 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~186
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 604 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 Garnavillo's average, not your lot's — a low corner or a tree line moves it. Against Garnavillo's 186-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Garnavillo
Each reading below is measured for Garnavillo itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredGarnavillo runs about 186 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
MeasuredGarnavillo 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 Garnavillo is in
Garnavillo sits in the Driftless Area — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Garnavillo's own centroid rather than borrowed from Clayton County.
What Grows in Garnavillo
Every plant below cleared Garnavillo's own zone 5a and its 186-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Garnavillo?
Usually not — gardeners here simply switch what goes in the ground as the season moves. 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 19 — 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 Garnavillo
Closest first, within ~10 miles of Garnavillo. Listing isn't leaking, and distance isn't exposure.
- THREE RIVERS FS COMPANYUnderground Storage Tanks · 450 ft
- 093N03W18DCAB 07810 1956Garnavillo 2Nitrate · 500 ft
- IDHE''S 66 SERVICEUnderground Storage Tanks · 550 ft
- 093N03W18DDAD 1924GarnavilloNitrate · 750 ft
- JACKS 66Underground Storage Tanks · 800 ft
- CITY OF GARNAVILLOUnderground Storage Tanks · 950 ft
- LONG LASTING FARM EQUIPMENTUnderground Storage Tanks · 1200 ft
- 093N03W18DAAD 1976Garnavillo 4Nitrate · 1200 ft
- GARNAVILLO MILL INCUnderground Storage Tanks · 1300 ft
- KIST BOTTLING CO INCUnderground Storage Tanks · 1500 ft
- GARNAVILLO OIL COUnderground Storage Tanks · 1700 ft
- TOP GUN CUSTOMSBrownfields · 1800 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Garnavillo'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 Garnavillo.
Total Sites
148
within ~10 miles of Garnavillo
Risk Level
Elevated
Highest-severity
3 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Garnavillo
Severity Distribution
within ~10 miles of Garnavillo
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Garnavillo, two things run higher than the national average within ~10 miles of Garnavillo — Mining (9 sites) and Underground Storage Tanks (92 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Garnavillo
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 Garnavillo average
Your land is one point inside Garnavillo
Everything above resolves to Garnavillo as a whole — one PHZM band and one 28°F frost record, read across 604 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 Garnavillo Average
Garnavillo Average
- ●USDA Zones 5a, averaged across Garnavillo
- ●One soil character for all of Garnavillo
- ●Frost dates read at Garnavillo's scale: Apr 16 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Garnavillo's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Garnavillo
Pull a site-specific report for your exact address in Garnavillo, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Garnavillo averages can't show:
We read public map data around Garnavillo — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Garnavillo average
How we know this about Garnavillo
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 Garnavillo’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 Garnavillo
When does frost risk typically end in Garnavillo?
The last hard freeze (28°F) in Garnavillo 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 Garnavillo?
The first hard freeze (28°F) in Garnavillo 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 186 days after the spring freeze cleared.
How long is the growing season in Garnavillo?
Measured between 28°F hard freezes, Garnavillo sees about 186 frost-free days — roughly Apr 16 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 7 to Oct 5, about 151 days.
Is the soil safe to grow vegetables in Garnavillo?
The federal record around Garnavillo is a meaningful one — 148 documented sites, mostly Underground Storage Tanks entries (92), the nearest Underground Storage Tanks 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 Garnavillo?
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 Garnavillo's scale — its 5a band and its 186-day season. Your yard writes its own version of Garnavillo'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 Garnavillo’s own scale
6 of the readings below were taken at Garnavillo's own scale — its own ~186-day season between 28°F freezes, the 604 acres it covers and 148 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Garnavillo's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Garnavillo's own 28°F hard-freeze dates, about Apr 16 and Oct 19 and the ~186-day span between themNOAA 1991–2020 Climate Normals
- 148 documented contamination sites on the federal record near Garnavillo, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Garnavillo's boundary and the 604 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~186-day seasonGrowable Ground crop-matching engine
- The ecoregion at Garnavillo's own centroid, the Driftless AreaUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Garnavillo's 604 acres read through its county's SSURGO summaryfrom Clayton County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Clayton 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 Clayton County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Garnavillo's 604 acreswhy one lot differs from the next →
- Which side of Garnavillo you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 604 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 Garnavillo-wide figureread your own land →
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