Iosco County, in Michigan, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
These conditions suit cabbage, hazelnut, lavender, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Iosco County holds more than one microclimate.
Soils and elevations shift across Iosco 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 Iosco County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Iosco County — the short answer
Iosco County, Michigan: USDA zone 6a, about 181 days between hard freezes, across 352K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 29
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 27
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~181
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 352K 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 6a is Iosco County's average, not your lot's — a low corner or a tree line moves it. Against Iosco County's 181-day season, see what your own ground reads.
Heat in Iosco County
Across a year, Iosco County accumulates about 2,034 growing degree days above 50°F, about 66 fewer than the middle Michigan county — ahead of 38 of Michigan’s 83 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 Iosco County
Across Iosco County, the ground is predominantly Entisols, where Grayling, Deford, and Kawkawlin are the most extensive named soil series. The soil is generally excessively drained with a sand surface. Topsoil pH runs about 4.8–6.2, strongly acidic. Rainfall drains through hydrologic group A soils.
Soil order
Entisols
Drainage
Excessively drained
Prime farmland
4%
Hydric soils
23%
Soil still varies lot by lot — soil types explained.
How the ground varies across Iosco County
The USDA soil survey maps 31% of Iosco County as excessively drained — but another 65% drains differently: 23% somewhat poorly drained, 18% very poorly drained.
Grayling is the most extensive named soil at 25% of mapped acres, then Deford (5%) and Kawkawlin (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 Iosco County
Each reading below is measured for Iosco 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 Iosco County are excessively drained, in hydrologic group A — 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 Iosco County runs about pH 4.8–6.2, 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 23% of Iosco 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
MeasuredIosco County runs about 181 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 Iosco County is in
Iosco 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 Iosco County
We scored all 1,086 plants against Iosco County's own USDA zone 6a and its own 181-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 Iosco 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 Apr 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 27 — 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 Iosco County
- monarch butterfly7 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Iosco County
USGS estimates 4,410 lb of Glyphosate on Iosco County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (2,350 lb) and Metolachlor-s (1,508 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 Iosco County — and how to grow with it.
We checked the federal record across Iosco County — 295 documented sites across 6 of the 9 source types we track.
The most significant on record: 3 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Iosco County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Iosco County
Closest first, across Iosco County. Listing isn't leaking, and distance isn't exposure.
- Oscoda Manufacturing Former SiteUnderground Storage Tanks · 1.8 mi
- TIP TOP SCREWBrownfields · 1.9 mi
- TIP TOP SCREWToxics Release Inventory · 1.9 mi
- HEDBLUM INDUSTRIESSuperfund · 2.3 mi
- HEDBLUM INDUSTRIESBrownfields · 2.3 mi
- Ralph Scott Excavating IncUnderground Storage Tanks · 2.5 mi
- HURON COLLISIONBrownfields · 2.5 mi
- Iosco County Road CommissionUnderground Storage Tanks · 2.5 mi
- Oscoda Area SchoolsUnderground Storage Tanks · 2.6 mi
- Oscoda School Bus GarageUnderground Storage Tanks · 2.6 mi
- River Rd. ElementaryUnderground Storage Tanks · 2.6 mi
- COOPER STANDARD AUTOMOTIVE INCToxics Release Inventory · 2.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Iosco 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 Iosco County.
Sources Checked
across Iosco County
Severity Distribution
across Iosco 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 Iosco 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 Iosco County average
Your land is one point inside Iosco County
Everything above resolves to Iosco County as a whole — one PHZM band and one county frost record, read across 352K 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 Iosco County Average
Iosco County Average
- ●USDA Zones 6a, averaged across Iosco County
- ●One soil character for all of Iosco County
- ●Frost dates read at Iosco County's scale: Apr 29 to Oct 27
YOUR Parcel
- ✓Your exact zone, not Iosco County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Iosco County
Pull a site-specific report for your exact address in Iosco County, Michigan — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Iosco County averages can't show:
We read public map data around Iosco County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iosco County average
How we know this about Iosco 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 Iosco County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Iosco County
When does frost risk typically end in Iosco County?
The last hard freeze (28°F) in Iosco County typically lands around Apr 29, 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 20.
How long is the growing season in Iosco County?
Measured between 28°F hard freezes, Iosco County sees about 181 frost-free days — roughly Apr 29 through Oct 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 20 to Oct 13, about 146 days.
Is the soil safe to grow vegetables in Iosco County?
The federal record around Iosco County is a meaningful one — 295 documented sites, mostly Underground Storage Tanks entries (143), the nearest Underground Storage Tanks record about 1.8 miles 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.
Everything above is measured at Iosco County's scale — its 6a band and its 181-day season. Your yard writes its own version of Iosco 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 Iosco County’s own scale
9 of the readings below were taken at Iosco County's own scale — its own ~181-day span between 28°F freezes, the 3 most extensive soil series mapped here and 295 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Iosco County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Iosco County's own 28°F hard-freeze dates and its ~181-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Iosco CountyUSDA NRCS SSURGO
- 295 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.8 miles outFederal environmental registers
- Iosco County's boundary and the 351,665 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~181-day seasonGrowable Ground crop-matching engine
- Iosco County sitting wholly inside the Northern Lakes and ForestsUS EPA Level III Ecoregions
- Open occurrence records documented in Iosco County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Iosco 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 Iosco County — the ~181 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 Iosco County's 351,665 acreswhy one lot differs from the next →
- Which of those 295 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 Iosco Countyread your own land →