Monona County, in Iowa, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Monona County lies within the Loess Hills — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Monona County holds more than one microclimate.
Soils and elevations shift across Monona County, so your frost dates and drainage aren't the county average. 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 Monona County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Monona County — the short answer
Monona County, Iowa: USDA zone 5a, about 190 days between hard freezes, across 444K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 13
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~190
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 444K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 Monona County's average, not your lot's — a low corner or a tree line moves it. Against Monona County's 190-day season, see what your own ground reads.
Heat in Monona County
Across a year, Monona County accumulates about 2,908 growing degree days above 50°F, about 164 more than the middle Iowa county — ahead of 62 of Iowa’s 99 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Monona County
Across Monona County, the ground is predominantly Entisols, where Ida, Napier, and Luton are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.7–7.7, neutral. Rainfall drains through hydrologic group B soils.
Soil order
Entisols
Drainage
Well drained
Prime farmland
26%
Hydric soils
30%
Soil still varies lot by lot — soil types explained.
How the ground varies across Monona County
The USDA soil survey maps 49% of Monona County as well drained — but another 50% drains differently: 28% poorly drained, 11% somewhat poorly drained.
Ida is the most extensive named soil at 18% of mapped acres, then Napier (14%) and Luton (14%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Monona County
Each reading below is measured for Monona County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Monona County are well drained, in hydrologic group B — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Monona County runs about pH 6.7–7.7, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 30% of Monona County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredMonona County runs about 190 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
The kind of country Monona County is in
Monona County sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Monona County
We scored all 1,086 plants against Monona County's own USDA zone 5a and its own 190-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Iowa profile.
Is it too late to plant in Monona County?
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 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 13 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — 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.
Documented around Monona County
- monarch butterfly8 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Monona County
USGS estimates 344,784 lb of Glyphosate on Monona County farmland in 2019, its largest by weight, ahead of Acetochlor (131,949 lb) and Metolachlor & Metolachlor-s (111,411 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Monona County — and how to grow with it.
We checked the federal record across Monona County — 175 documented sites across 5 of the 9 source types we track.
The most significant on record: 5 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Monona County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Monona County
Closest first, across Monona County. Listing isn't leaking, and distance isn't exposure.
- Turin-RotnickeNitrate · 1.9 mi
- Turin-WagnerNitrate · 1.9 mi
- NW FARM SERVICE COUnderground Storage Tanks · 2.1 mi
- MONONA COUNTY ENGINEERSUnderground Storage Tanks · 2.1 mi
- 084N44W24CAAC 1963Castana 2Nitrate · 2.6 mi
- 084N44W24CAAC 1957Castana 1Nitrate · 2.6 mi
- PHIPPS SERVICEUnderground Storage Tanks · 2.6 mi
- 084N44W24DBBC 01353 1939Castana 2Nitrate · 2.7 mi
- ISU WESTERN RESEARCH CENTERUnderground Storage Tanks · 2.9 mi
- AT&T COMMUNICATIONSUnderground Storage Tanks · 2.9 mi
- 084N44W24AACC 1940Castana NorthNitrate · 3.1 mi
- 083N43W04CBCB 26333 1981IGS & USGS WC-5ANitrate · 4.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Monona County'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 Monona County.
Total Sites
175
across Monona County
Risk Level
Moderate
Highest-severity
5 Toxics Release Inventory facilities
Sources Checked
across Monona County
Severity Distribution
across Monona County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Monona County, Nitrate runs higher than the national average — 70 sites across Monona County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Monona County
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 Monona County average
Your land is one point inside Monona County
Everything above resolves to Monona County as a whole — one PHZM band and one county frost record, read across 444K 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 county 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 county average.
Your Lot vs the Monona County Average
Monona County Average
- ●USDA Zones 5a, averaged across Monona County
- ●One soil character for all of Monona County
- ●Frost dates read at Monona County's scale: Apr 13 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Monona County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Monona County
Pull a site-specific report for your exact address in Monona County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Monona County averages can't show:
We read public map data around Monona County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Monona County average
How we know this about Monona County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Monona County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Monona County
When does frost risk typically end in Monona County?
The last hard freeze (28°F) in Monona County typically lands around Apr 13, 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 4.
How long is the growing season in Monona County?
Measured between 28°F hard freezes, Monona County sees about 190 frost-free days — roughly Apr 13 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 4 to Oct 6, about 155 days.
Is the soil safe to grow vegetables in Monona County?
The federal record around Monona County shows 175 documented sites, mostly Underground Storage Tanks entries (88), the nearest Nitrate record about 1.9 miles 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.
Everything above is measured at Monona County's scale — its 5a band and its 190-day season. Your yard writes its own version of Monona County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Iowa's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Monona County’s own scale
9 of the readings below were taken at Monona County's own scale — its own ~190-day span between 28°F freezes, the 3 most extensive soil series mapped here and 175 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Monona County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Monona County's own 28°F hard-freeze dates and its ~190-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Monona CountyUSDA NRCS SSURGO
- 175 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 1.9 miles outFederal environmental registers
- Monona County's boundary and the 444,206 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~190-day seasonGrowable Ground crop-matching engine
- Monona County sitting wholly inside the Western Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Monona County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Monona County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
What this page can’t tell you
- How the season shifts across Monona County — the ~190 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Monona County's 444,206 acreswhy one lot differs from the next →
- Which of those 175 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Monona Countyread your own land →