Seminole County, in Oklahoma, sits in USDA hardiness zone 7b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Crops well matched to these conditions include cabbage, prickly pear, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Seminole County holds more than one microclimate.
Soils and elevations shift across Seminole 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 Seminole County — soil, climate, flood, and parcel records. How we handle your address.
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Seminole County — the short answer
Seminole County, Oklahoma: USDA zone 7b, about 240 days between hard freezes, across 405K acres.
- USDA zone
- 7b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 16
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 11
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~240
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 405K 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 7b is Seminole County's average, not your lot's — a low corner or a tree line moves it. Against Seminole County's 240-day season, see what your own ground reads.
Heat and winter chill in Seminole County
Across a year, Seminole County accumulates about 4,832 growing degree days above 50°F, about 112 more than the middle Oklahoma county — ahead of 50 of Oklahoma’s 77 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.
Winter banks about 1,791 hours below 45°F, 128 fewer than the Oklahoma middle of 1,919. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Seminole County
Across Seminole County, the ground is predominantly Alfisols, where Stephenville, Seminole, and Darnell are the most extensive named soil series. The soil is generally well drained with a fine sandy loam surface. Topsoil pH runs about 5.8–6.5, slightly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
22%
Hydric soils
2%
Soil still varies lot by lot — soil types explained.
How the ground varies across Seminole County
The USDA soil survey maps 68% of Seminole County as well drained — but another 30% drains differently: 18% somewhat poorly drained, 10% moderately well drained.
Stephenville is the most extensive named soil at 26% of mapped acres, then Seminole (12%) and Darnell (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 Seminole County
Each reading below is measured for Seminole 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 Seminole 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 Seminole County runs about pH 5.8–6.5, 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
MeasuredSeminole County runs about 240 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
MeasuredSeminole County sits in USDA hardiness zone 7b.
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 Seminole County is in
Seminole County sits in the Cross Timbers — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Seminole County
We scored all 1,086 plants against Seminole County's own USDA zone 7b and its own 240-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 Oklahoma profile.
Is it too late to plant in Seminole 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 Feb 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 16 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 11 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
What gets applied to farmland in Seminole County
USGS estimates 24,092 lb of 2,4-d on Seminole County farmland in 2019, its largest by weight, ahead of Triclopyr (11,588 lb) and Dicamba (3,365 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 Seminole County — and how to grow with it.
We checked the federal record across Seminole County — 217 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.
There's a meaningful federal record across Seminole 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 Seminole County
Closest first, across Seminole County. Listing isn't leaking, and distance isn't exposure.
- New Lima SchoolsUnderground Storage Tanks · 1.1 mi
- Wood Oil Co.Underground Storage Tanks · 3.1 mi
- Halliburton ServicesUnderground Storage Tanks · 3.2 mi
- Commercial Brick CorporationUnderground Storage Tanks · 3.4 mi
- COMMERCIAL BRICKBrownfields · 3.4 mi
- COMMERCIAL BRICKToxics Release Inventory · 3.4 mi
- Farmer's Cooperative Gin CoUnderground Storage Tanks · 3.5 mi
- Atlantic Richfield CoUnderground Storage Tanks · 3.5 mi
- Bowlegs Public SchoolsUnderground Storage Tanks · 3.7 mi
- V W CootsUnderground Storage Tanks · 3.8 mi
- Dan ReynoldsUnderground Storage Tanks · 3.8 mi
- KOCH PIPELINE CO LP-WOLFBrownfields · 3.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Seminole 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 Seminole County.
Total Sites
217
across Seminole County
Risk Level
Elevated
Highest-severity
4 Superfund sites (none NPL-listed)
Severity Distribution
across Seminole County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Seminole County, two things run higher than the national average across Seminole County — PFAS (3 sites) and Superfund (4 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Seminole 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 Seminole County average
Your land is one point inside Seminole County
Everything above resolves to Seminole County as a whole — one PHZM band and one county frost record, read across 405K 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 Seminole County Average
Seminole County Average
- ●USDA Zones 7b, averaged across Seminole County
- ●One soil character for all of Seminole County
- ●Frost dates read at Seminole County's scale: Mar 16 to Nov 11
YOUR Parcel
- ✓Your exact zone, not Seminole County's 7b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Seminole County
Pull a site-specific report for your exact address in Seminole County, Oklahoma — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Seminole County averages can't show:
We read public map data around Seminole County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Seminole County average
How we know this about Seminole 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 Seminole County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Seminole County
When does frost risk typically end in Seminole County?
The last hard freeze (28°F) in Seminole County typically lands around Mar 16, 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 Apr 6.
How long is the growing season in Seminole County?
Measured between 28°F hard freezes, Seminole County sees about 240 frost-free days — roughly Mar 16 through Nov 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 6 to Oct 28, about 205 days.
Is the soil safe to grow vegetables in Seminole County?
The federal record around Seminole County is a meaningful one — 217 documented sites, mostly Underground Storage Tanks entries (162), the nearest Underground Storage Tanks record about 1.1 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 Seminole County's scale — its 7b band and its 240-day season. Your yard writes its own version of Seminole 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 Oklahoma's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Seminole County’s own scale
8 of the readings below were taken at Seminole County's own scale — its own ~240-day span between 28°F freezes, the 3 most extensive soil series mapped here and 217 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Seminole County's own USDA hardiness band, zones 7bUSDA PHZM 2023
- Seminole County's own 28°F hard-freeze dates and its ~240-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Seminole CountyUSDA NRCS SSURGO
- 217 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.1 miles outFederal environmental registers
- Seminole County's boundary and the 405,004 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7b and a ~240-day seasonGrowable Ground crop-matching engine
- Seminole County sitting wholly inside the Cross TimbersUS EPA Level III Ecoregions
- Which agricultural compounds go onto Seminole County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Oklahoma grower plans around — written at state scale, so they stay on the state guidefrom Oklahoma
What this page can’t tell you
- How the season shifts across Seminole County — the ~240 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 Seminole County's 405,004 acreswhy one lot differs from the next →
- Which of those 217 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 Seminole Countyread your own land →