Iron County, in Michigan, sits in USDA hardiness zone 4a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, cranberry, cilantro, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Iron County lies within the Upper Peninsula — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Iron County holds more than one microclimate.
Soils and elevations shift across Iron 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 Iron County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Iron County — the short answer
Iron County, Michigan: USDA zone 4a, about 126 days between hard freezes, across 746K acres.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 21
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Sep 24
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~126
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 746K 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 4a is Iron County's average, not your lot's — a low corner or a tree line moves it. Against Iron County's 126-day season, see what your own ground reads.
Heat in Iron County
Across a year, Iron County accumulates about 1,417 growing degree days above 50°F, about 683 fewer than the middle Michigan county — no other Michigan county banks fewer. 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 Iron County
Across Iron County, the ground is predominantly Spodosols, where Wabeno, Karlin, and Sundog are the most extensive named soil series. The soil is generally moderately well drained with a silt loam surface. Topsoil pH runs about 5.0–5.6, strongly acidic. Rainfall drains through hydrologic group A soils.
Soil order
Spodosols
Drainage
Moderately well drained
Prime farmland
5%
Hydric soils
21%
Soil still varies lot by lot — soil types explained.
How the ground varies across Iron County
The USDA soil survey maps 38% of Iron County as moderately well drained — but another 58% drains differently: 23% well drained, 15% very poorly drained.
Wabeno is the most extensive named soil at 13% of mapped acres, then Karlin (7%) and Sundog (6%).
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 Iron County
Each reading below is measured for Iron 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 Iron County are moderately well drained, in hydrologic group A — 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 Iron County runs about pH 5.0–5.6, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 21% of Iron 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
MeasuredIron County runs about 126 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
The kind of country Iron County is in
Iron County sits in the Northern Lakes and Forests — EPA Level III, inside the wider Northern Forests. One consistent ecological setting across the whole county.
What Grows in Iron County
We scored all 1,086 plants against Iron County's own USDA zone 4a and its own 126-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 Michigan profile.
Is it too late to plant in Iron County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 24 — long-season crops need about 90 days of runway, quick greens only 30. In a season this compact, fast finishers and cold-hardy greens do the late work, and garlic tucked in before the freeze repays you next summer.
Documented around Iron County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Iron County
USGS estimates 1,866 lb of Metolachlor & Metolachlor-s on Iron County farmland in 2019, its largest by weight, ahead of Metolachlor-s (1,542 lb) and Glyphosate (1,307 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 Iron County — and how to grow with it.
We checked the federal record across Iron County — 135 documented sites across 4 of the 9 source types we track.
The most significant on record: 1 Toxics Release Inventory facility. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Iron 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 Iron County
Closest first, across Iron County. Listing isn't leaking, and distance isn't exposure.
- IRON 43-34 PAS09Nitrate · 4.8 mi
- Bates Elementary SchoolUnderground Storage Tanks · 4.9 mi
- GRIFFS BODY SHOPBrownfields · 5.1 mi
- Iron River Service CenterUnderground Storage Tanks · 5.1 mi
- MICHIGAN AUTOMATICS INCBrownfields · 5.2 mi
- Eugene JamesUnderground Storage Tanks · 5.5 mi
- Heimerl BrosUnderground Storage Tanks · 5.7 mi
- WHITE WATER ASSOCIATESBrownfields · 6.0 mi
- MICHIGAN CONSOLIDATED GAS COBrownfields · 6.0 mi
- GREAT LAKES GAS TRANSMISSION STATION #8Brownfields · 6.0 mi
- 44N 33W 08AAAA01 IRON CO (AMASA)Nitrate · 6.0 mi
- Tall Pines GroceryUnderground Storage Tanks · 6.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Iron 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 Iron County.
Total Sites
135
across Iron County
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
across Iron County
Severity Distribution
across Iron County
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Iron 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 Iron County average
Your land is one point inside Iron County
Everything above resolves to Iron County as a whole — one PHZM band and one county frost record, read across 746K 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 Iron County Average
Iron County Average
- ●USDA Zones 4a, averaged across Iron County
- ●One soil character for all of Iron County
- ●Frost dates read at Iron County's scale: May 21 to Sep 24
YOUR Parcel
- ✓Your exact zone, not Iron County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Iron County
Pull a site-specific report for your exact address in Iron County, Michigan — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Iron County averages can't show:
We read public map data around Iron County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iron County average
How we know this about Iron 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 Iron County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Iron County
When does frost risk typically end in Iron County?
The last hard freeze (28°F) in Iron County typically lands around May 21, 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 Jun 11.
How long is the growing season in Iron County?
Measured between 28°F hard freezes, Iron County sees about 126 frost-free days — roughly May 21 through Sep 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 11 to Sep 10, about 91 days.
Is the soil safe to grow vegetables in Iron County?
The federal record around Iron County shows 135 documented sites, mostly Underground Storage Tanks entries (72), the nearest Nitrate record about 4.8 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.
How do gardeners stretch the season in Iron County?
With about 126 frost-free days between hard freezes, Iron County rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 154 to 182 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 21 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Iron County's scale — its 4a band and its 126-day season. Your yard writes its own version of Iron 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 Michigan's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Iron County’s own scale
9 of the readings below were taken at Iron County's own scale — its own ~126-day span between 28°F freezes, the 3 most extensive soil series mapped here and 135 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Iron County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Iron County's own 28°F hard-freeze dates and its ~126-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Iron CountyUSDA NRCS SSURGO
- 135 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 4.8 miles outFederal environmental registers
- Iron County's boundary and the 746,313 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~126-day seasonGrowable Ground crop-matching engine
- Iron County sitting wholly inside the Northern Lakes and ForestsUS EPA Level III Ecoregions
- Open occurrence records documented in Iron County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Iron County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Michigan grower plans around — written at state scale, so they stay on the state guidefrom Michigan
What this page can’t tell you
- How the season shifts across Iron County — the ~126 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 Iron County's 746,313 acreswhy one lot differs from the next →
- Which of those 135 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 Iron Countyread your own land →