Madison County, in Iowa, sits in USDA hardiness zone 5b — 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.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Madison County holds more than one microclimate.
Soils and elevations shift across Madison 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 Madison County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Madison County — the short answer
Madison County, Iowa: USDA zone 5b, about 192 days between hard freezes, across 359K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 12
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 21
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~192
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 359K 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 5b is Madison County's average, not your lot's — a low corner or a tree line moves it. Against Madison County's 192-day season, see what your own ground reads.
Heat in Madison County
Across a year, Madison County accumulates about 2,911 growing degree days above 50°F, about 167 more than the middle Iowa county — ahead of 63 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 Madison County
Across Madison County, the ground is predominantly Alfisols, where Sharpsburg, Ladoga, and Gara are the most extensive named soil series. The soil is generally moderately well drained with a silty clay loam surface. Topsoil pH runs about 6.2–6.5, slightly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Moderately well drained
Prime farmland
27%
Hydric soils
15%
Soil still varies lot by lot — soil types explained.
How the ground varies across Madison County
The USDA soil survey maps 42% of Madison County as moderately well drained — but another 55% drains differently: 22% well drained, 17% somewhat poorly drained.
Sharpsburg is the most extensive named soil at 14% of mapped acres, then Ladoga (12%) and Gara (11%).
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 Madison County
Each reading below is measured for Madison 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 Madison County are moderately well drained, in hydrologic group C — roughly the middle of the drainage range.
This is close to the middle most vegetables prefer: it holds enough water to carry a crop between rains without staying waterlogged. The catch is that a wet spring or a low corner can still tip it soggy.
Plant on the site as-is for most crops, but keep the lowest, slowest-draining beds for moisture-tolerant plantings.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Madison County runs about pH 6.2–6.5, 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
Season length
MeasuredMadison County runs about 192 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
MeasuredMadison County 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 Madison County is in
Madison 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 Madison County
We scored all 1,086 plants against Madison County's own USDA zone 5b and its own 192-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 Madison County?
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 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 21 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Madison County
- Japanese beetle2 documented records
- monarch butterfly98 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Madison County
USGS estimates 106,772 lb of Glyphosate on Madison County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (57,514 lb) and Atrazine (49,952 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 Madison County — and how to grow with it.
We checked the federal record across Madison County — 100 documented sites across 5 of the 9 source types we track.
The most significant on record: 3 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Madison 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 Madison County
Closest first, across Madison County. Listing isn't leaking, and distance isn't exposure.
- WINTERSET COMM. SCHOOLSUnderground Storage Tanks · 200 ft
- GIT-N-GO #21Underground Storage Tanks · 600 ft
- IOWA DEPT OF TRANSPORTATIONUnderground Storage Tanks · 800 ft
- MADISON COUNTY MEMORIAL HOSPITALUnderground Storage Tanks · 850 ft
- J & D OIL COUnderground Storage Tanks · 1100 ft
- KUM & GO #246Underground Storage Tanks · 1200 ft
- FORMER UNITED FEDERAL SAVINGS BANKUnderground Storage Tanks · 1300 ft
- CASEY''S GENERAL STORE 1062Underground Storage Tanks · 1300 ft
- U S WESTUnderground Storage Tanks · 1400 ft
- MADISON COUNTY TIRE INCBrownfields · 1600 ft
- FORMER MEYER SERVICE CENTERUnderground Storage Tanks · 1600 ft
- GRIP TITE MFG COBrownfields · 1800 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Madison 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 Madison County.
Total Sites
100
across Madison County
Risk Level
Moderate
Highest-severity
3 Toxics Release Inventory facilities
Sources Checked
across Madison County
Severity Distribution
across Madison County
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 Madison 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 Madison County average
Your land is one point inside Madison County
Everything above resolves to Madison County as a whole — one PHZM band and one county frost record, read across 359K 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 Madison County Average
Madison County Average
- ●USDA Zones 5b, averaged across Madison County
- ●One soil character for all of Madison County
- ●Frost dates read at Madison County's scale: Apr 12 to Oct 21
YOUR Parcel
- ✓Your exact zone, not Madison County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Madison County
Pull a site-specific report for your exact address in Madison County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Madison County averages can't show:
We read public map data around Madison County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Madison County average
How we know this about Madison 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 Madison County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Madison County
When does frost risk typically end in Madison County?
The last hard freeze (28°F) in Madison County typically lands around Apr 12, 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 3.
How long is the growing season in Madison County?
Measured between 28°F hard freezes, Madison County sees about 192 frost-free days — roughly Apr 12 through Oct 21, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 3 to Oct 7, about 157 days.
Is the soil safe to grow vegetables in Madison County?
The federal record around Madison County shows 100 documented sites, mostly Underground Storage Tanks entries (61), the nearest Underground Storage Tanks record under a tenth of a mile 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 Madison County's scale — its 5b band and its 192-day season. Your yard writes its own version of Madison 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 Madison County’s own scale
9 of the readings below were taken at Madison County's own scale — its own ~192-day span between 28°F freezes, the 3 most extensive soil series mapped here and 100 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Madison County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Madison County's own 28°F hard-freeze dates and its ~192-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Madison CountyUSDA NRCS SSURGO
- 100 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record under a tenth of a mile outFederal environmental registers
- Madison County's boundary and the 359,044 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~192-day seasonGrowable Ground crop-matching engine
- Madison County sitting wholly inside the Western Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Madison County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Madison 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 Madison County — the ~192 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 Madison County's 359,044 acreswhy one lot differs from the next →
- Which of those 100 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 Madison Countyread your own land →