Iron County, in Utah, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
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, Utah: USDA zone 5b, about 158 days between hard freezes, across 2.1M acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 9
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~158
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 2.1M 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 Iron County's average, not your lot's — a low corner or a tree line moves it. Against Iron County's 158-day season, see what your own ground reads.
Heat in Iron County
Across a year, Iron County accumulates about 2,512 growing degree days above 50°F, right at the Utah middle — ahead of 14 of Utah’s 29 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 Iron County
Across Iron County, the ground is predominantly Aridisols, where Checkett, Taylorsflat, and Sevy are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.6–8.2, slightly alkaline. Rainfall drains through hydrologic group C soils.
Soil order
Aridisols
Drainage
Well drained
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Iron County
The USDA soil survey maps 97% of Iron County as well drained — but another 2% drains differently: 1% somewhat excessively drained.
Checkett is the most extensive named soil at 7% of mapped acres, then Taylorsflat (5%) and Sevy (5%).
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 well drained, in hydrologic group C — 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 Iron County runs about pH 7.6–8.2, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredIron County runs about 158 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
MeasuredIron 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 Iron County is in
Iron County spans 2 EPA Level III ecoregions — Central Basin and Range (79%) and Wasatch and Uinta Mountains (21%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Iron County
We scored all 1,086 plants against Iron County's own USDA zone 5b and its own 158-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 Utah 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 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 9 — 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 gets applied to farmland in Iron County
USGS estimates 19,698 lb of Glyphosate on Iron County farmland in 2019, its largest by weight, ahead of Chlorpyrifos (8,083 lb) and Dimethoate (4,176 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 — 482 documented sites across 8 of the 9 source types we track.
The most significant on record: 4 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Iron County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
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.
- (C-33-13) 3caa- 1Nitrate · 3.5 mi
- Cina-MineMining · 4.2 mi
- Unnamed ProspectMining · 4.2 mi
- Homestake MineMining · 4.2 mi
- (C-34-13)16ccc- 1Nitrate · 5.0 mi
- (C-33-12)11aaa- 1Nitrate · 8.4 mi
- (C-33-12)11aaa- 2Nitrate · 8.4 mi
- (C-32-13) 9bdd- 3Nitrate · 8.6 mi
- (C-32-14)21bcd- 1Nitrate · 9.6 mi
- (C-32-14)21bad- 1Nitrate · 9.6 mi
- LUND STATIONUnderground Storage Tanks · 9.6 mi
- MUSKET CEDAR CITY BULK PLANTToxics Release Inventory · 10.7 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.
Severity Distribution
across Iron County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Iron County, two things run higher than the national average across Iron County — Mining (81 sites) and Nitrate (180 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
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 2.1M 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 5b, averaged across Iron County
- ●One soil character for all of Iron County
- ●Frost dates read at Iron County's scale: May 4 to Oct 9
YOUR Parcel
- ✓Your exact zone, not Iron County's 5b
- ✓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, Utah — 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 4, 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 25.
How long is the growing season in Iron County?
Measured between 28°F hard freezes, Iron County sees about 158 frost-free days — roughly May 4 through Oct 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 25, about 123 days.
Is the soil safe to grow vegetables in Iron County?
The federal record around Iron County runs heavier than most — 482 documented sites, mostly Nitrate entries (180), the nearest Nitrate record about 3.5 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Everything above is measured at Iron County's scale — its 5b band and its 158-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 Utah's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Iron County’s own scale
8 of the readings below were taken at Iron County's own scale — its own ~158-day span between 28°F freezes, the 3 most extensive soil series mapped here and 482 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 5bUSDA PHZM 2023
- Iron County's own 28°F hard-freeze dates and its ~158-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
- 482 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 3.5 miles outFederal environmental registers
- Iron County's boundary and the 2,109,545 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~158-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Iron County spans, Central Basin and Range the largestUS EPA Level III Ecoregions
- 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 Utah grower plans around — written at state scale, so they stay on the state guidefrom Utah
What this page can’t tell you
- How the season shifts across Iron County — the ~158 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 2,109,545 acreswhy one lot differs from the next →
- Which of those 482 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 →