Zwingle, Iowa, sits in USDA hardiness zone 5a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Zwingle, 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 Zwingle 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 Zwingle — soil, climate, flood, and parcel records. How we handle your address.
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Zwingle — the short answer
Zwingle, Iowa: USDA zone 5a, about 191 days between hard freezes, across 104 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 14
- 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
- ~191
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 104 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 Zwingle's average, not your lot's — a low corner or a tree line moves it. Against Zwingle's 191-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Zwingle
Each reading below is measured for Zwingle itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredZwingle runs about 191 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
MeasuredZwingle 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 Zwingle is in
Zwingle sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Zwingle's own centroid, and it is not what its county reads: Dubuque County is mostly Driftless Area. The wider page above you is answering a different question about different ground.
What Grows in Zwingle
Every plant below cleared Zwingle's own zone 5a and its 191-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Zwingle?
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 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 14 (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. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Zwingle
Closest first, within ~10 miles of Zwingle. Listing isn't leaking, and distance isn't exposure.
- 087N02E35DDBNitrate · 400 ft
- Zwingle Mines and OccurrencesMining · 750 ft
- LAMOTTE SHOP-SECONDARY ROADS DEPTBrownfields · 2.9 mi
- DARREL COMERUnderground Storage Tanks · 3.0 mi
- BULLOCK AG SERVICE INCUnderground Storage Tanks · 3.0 mi
- CLASEN''S 76Underground Storage Tanks · 3.4 mi
- 087N03E33CDD 11757 1959La Motte 1Nitrate · 3.5 mi
- COUNTY SHED #1Underground Storage Tanks · 3.5 mi
- Graham Mill-ConcentratorMining · 3.7 mi
- 087N03E33DC 01291 1940La Motte 2Nitrate · 3.8 mi
- SNK GAS & FOODUnderground Storage Tanks · 3.9 mi
- COUNTY SHED #5Underground Storage Tanks · 4.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Zwingle'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 Zwingle.
Total Sites
56
within ~10 miles of Zwingle
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Zwingle
Severity Distribution
within ~10 miles of Zwingle
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Zwingle, Mining runs higher than the national average — 5 sites within ~10 miles of Zwingle. That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Zwingle
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 Zwingle average
Your land is one point inside Zwingle
Everything above resolves to Zwingle as a whole — one PHZM band and one 28°F frost record, read across 104 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 Zwingle Average
Zwingle Average
- ●USDA Zones 5a, averaged across Zwingle
- ●One soil character for all of Zwingle
- ●Frost dates read at Zwingle's scale: Apr 14 to Oct 22
YOUR Parcel
- ✓Your exact zone, not Zwingle's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Zwingle
Pull a site-specific report for your exact address in Zwingle, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Zwingle averages can't show:
We read public map data around Zwingle — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Zwingle average
How we know this about Zwingle
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 Zwingle’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 Zwingle
When does frost risk typically end in Zwingle?
The last hard freeze (28°F) in Zwingle typically lands around Apr 14, 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 5.
When is the first frost in Zwingle?
The first hard freeze (28°F) in Zwingle 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 191 days after the spring freeze cleared.
How long is the growing season in Zwingle?
Measured between 28°F hard freezes, Zwingle sees about 191 frost-free days — roughly Apr 14 through Oct 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 5 to Oct 8, about 156 days.
Is the soil safe to grow vegetables in Zwingle?
The federal record around Zwingle is a meaningful one — 56 documented sites, mostly Underground Storage Tanks entries (24), the nearest Nitrate 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 Zwingle?
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 Zwingle's scale — its 5a band and its 191-day season. Your yard writes its own version of Zwingle'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 Zwingle’s own scale
6 of the readings below were taken at Zwingle's own scale — its own ~191-day season between 28°F freezes, the 104 acres it covers and 56 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Zwingle's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Zwingle's own 28°F hard-freeze dates, about Apr 14 and Oct 22 and the ~191-day span between themNOAA 1991–2020 Climate Normals
- 56 documented contamination sites on the federal record near Zwingle, the closest Nitrate record under a tenth of a mile out from the town centreFederal environmental registers
- Zwingle's boundary and the 104 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~191-day seasonGrowable Ground crop-matching engine
- Zwingle sits in the Western Corn Belt Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Zwingle's 104 acres read through its county's SSURGO summaryfrom Dubuque County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Dubuque 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 Dubuque County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Zwingle's 104 acreswhy one lot differs from the next →
- Which side of Zwingle you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 104 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate 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 Zwingle-wide figureread your own land →
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