Union County, in Ohio, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
On paper, cabbage, hazelnut, lavender, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Union County holds more than one microclimate.
Soils and elevations shift across Union 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 Union County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Union County — the short answer
Union County, Ohio: USDA zone 6a, about 208 days between hard freezes, across 276K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 10
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 4
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~208
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 276K 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 Union County's average, not your lot's — a low corner or a tree line moves it. Against Union County's 208-day season, see what your own ground reads.
Heat in Union County
Across a year, Union County accumulates about 3,008 growing degree days above 50°F, about 86 more than the middle Ohio county — ahead of 58 of Ohio’s 88 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 Union County
Across Union County, the ground is predominantly Alfisols, where Blount, Glynwood, and Wetzel are the most extensive named soil series. The soil is generally somewhat poorly drained with a silt loam surface. Topsoil pH runs about 6.3–6.4, slightly acidic. Rainfall drains through hydrologic group D soils.
Soil order
Alfisols
Drainage
Somewhat poorly drained
Prime farmland
13%
Hydric soils
31%
Soil still varies lot by lot — soil types explained.
How the ground varies across Union County
The USDA soil survey maps 53% of Union County as somewhat poorly drained — but another 47% drains differently: 16% poorly drained, 14% very poorly drained.
Blount is the most extensive named soil at 41% of mapped acres, then Glynwood (10%) and Wetzel (10%).
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 Union County
Each reading below is measured for Union 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 Union County are somewhat poorly drained, in hydrologic group D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Union County runs about pH 6.3–6.4, 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
MeasuredUnion County runs about 208 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredUnion County sits in USDA hardiness zone 6a.
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 Union County is in
Union County sits in the Eastern Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Union County
We scored all 1,086 plants against Union County's own USDA zone 6a and its own 208-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 Ohio profile.
Is it too late to plant in Union County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 4 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
Documented around Union County
Spotted lanternfly documented 26 miles from Union County, first recorded 2022. What to watch for.
What gets applied to farmland in Union County
USGS estimates 97,411 lb of Glyphosate on Union County farmland in 2019, its largest by weight, ahead of Atrazine (38,402 lb) and Acetochlor (30,833 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 Union County — and how to grow with it.
We checked the federal record across Union County — 229 documented sites across 5 of the 9 source types we track.
The most significant on record: 5 Superfund sites (none NPL-listed). 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 Union 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 Union County
Closest first, across Union County. Listing isn't leaking, and distance isn't exposure.
- VACANT LOTUnderground Storage Tanks · 1.2 mi
- UNION RURAL ELECTRIC COOP., INC.Underground Storage Tanks · 3.1 mi
- BOB DEGROOTUnderground Storage Tanks · 3.1 mi
- UNION COUNTY COMMISSIONERSUnderground Storage Tanks · 3.1 mi
- FORMER TRUCK STOPUnderground Storage Tanks · 3.1 mi
- VILLAGE PANTRY #2712Underground Storage Tanks · 3.3 mi
- KMART # 7646Brownfields · 3.3 mi
- MARYSVILLE EARLY COLLEGE HIGH SCHOOLBrownfields · 3.4 mi
- MARYSVILLE CONCRETEUnderground Storage Tanks · 3.4 mi
- CITY OF MARYSVILLEUnderground Storage Tanks · 3.6 mi
- MARYSVILLE MIDDLE SCHOOLUnderground Storage Tanks · 3.7 mi
- AUTOWISE SERVICE & TIRE CENTERUnderground Storage Tanks · 3.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Union 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 Union County.
Total Sites
229
across Union County
Risk Level
Elevated
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
across Union County
Severity Distribution
across Union County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Union County, two things run higher than the national average across Union County — Superfund (5 sites) and Toxics Release Inventory (14 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Union 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 Union County average
Your land is one point inside Union County
Everything above resolves to Union County as a whole — one PHZM band and one county frost record, read across 276K 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 Union County Average
Union County Average
- ●USDA Zones 6a, averaged across Union County
- ●One soil character for all of Union County
- ●Frost dates read at Union County's scale: Apr 10 to Nov 4
YOUR Parcel
- ✓Your exact zone, not Union County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Union County
Pull a site-specific report for your exact address in Union County, Ohio — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Union County averages can't show:
We read public map data around Union County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Union County average
How we know this about Union 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 Union County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Union County
When does frost risk typically end in Union County?
The last hard freeze (28°F) in Union County typically lands around Apr 10, 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 1.
How long is the growing season in Union County?
Measured between 28°F hard freezes, Union County sees about 208 frost-free days — roughly Apr 10 through Nov 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 1 to Oct 21, about 173 days.
Is the soil safe to grow vegetables in Union County?
The federal record around Union County is a meaningful one — 229 documented sites, mostly Underground Storage Tanks entries (97), the nearest Underground Storage Tanks record about 1.2 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 Union County's scale — its 6a band and its 208-day season. Your yard writes its own version of Union 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 Ohio's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Union County’s own scale
8 of the readings below were taken at Union County's own scale — its own ~208-day span between 28°F freezes, the 3 most extensive soil series mapped here and 229 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Union County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Union County's own 28°F hard-freeze dates and its ~208-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Union CountyUSDA NRCS SSURGO
- 229 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.2 miles outFederal environmental registers
- Union County's boundary and the 276,296 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~208-day seasonGrowable Ground crop-matching engine
- Union County sitting wholly inside the Eastern Corn Belt PlainsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Union County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Ohio grower plans around — written at state scale, so they stay on the state guidefrom Ohio
What this page can’t tell you
- How the season shifts across Union County — the ~208 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 Union County's 276,296 acreswhy one lot differs from the next →
- Which of those 229 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 Union Countyread your own land →