Harper County, in Oklahoma, sits in USDA hardiness zone 7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
A short list that earns its place here — pecan, tomato, okra, and redbud — with any one site's soil, sun, and drainage making the final cut.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Harper County holds more than one microclimate.
Soils and elevations shift across Harper County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Quick Facts
USDA Zones
7a
Last Hard Freeze (28°F)
Mar 8
County normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Nov 19
County normal — light frosts arrive a few weeks earlier
County Area
665K acres
Hardiness Zone Range
Zone maps are averages across Harper County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Harper County
Across Harper County, the ground is predominantly Inceptisols, where Quinlan, Selman, and Woodward are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.0–7.9, slightly alkaline. Rainfall drains through hydrologic group B soils.
Soil order
Inceptisols
Drainage
Well drained
Prime farmland
45%
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
What Grows in Harper County
Plants matched to Harper County's USDA zones 7a — each links to its full growing profile.
Is it too late to plant in Harper County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Feb 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 19 — 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.
Growing Challenges in Oklahoma
What an experienced grower plans around here — each one has a move.
Extreme weather variability (tornadoes, ice storms, drought)
Flexible beats fortified here: row covers staged, storm-tough perennials, and quick-replant annual beds.
Red clay soils drain poorly in central OK
A raised bed ends the standing-water fight in a weekend, and fall compost keeps opening the clay below.
Low western rainfall requires irrigation
Western plots run on drip and mulch — plan the water before the planting and the dry years lose their teeth.
For cultivar selection, pest pressure, and planting-time guidance specific to Oklahoma, the Oklahoma State University Extension is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Harper County — and how to grow with it.
We checked the federal record across Harper County — 169 documented sites across 4 of the 9 source types we track.
The most significant on record: 3 concentrated animal feeding operations. Large-scale animal operations that can contaminate soil and groundwater with nitrates and pathogens.
The federal record across Harper 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.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Total Sites
169
across Harper County
Risk Level
Moderate
Highest-severity
3 concentrated animal feeding operations
Sources Checked
across Harper County
Severity Distribution
across Harper County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Harper County, two things run higher than the national average — Nitrate (108 sites) and CAFO (3 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check your specific parcel in Harper County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
Harper County Average
- ●USDA Zones 7a
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Harper County
Pull a site-specific report for your exact address in Harper County, Oklahoma — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for Harper County, Oklahoma
- USDA Hardiness Zones: 7a (USDA PHZM 2023)
- Last Hard Freeze (28°F): Mar 8 (county normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Nov 19 (county normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~256 (county normal, NOAA 1991–2020 Climate Normals)
- County Land Area: 665K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Harper County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Harper County, Oklahoma?
Harper County sits in USDA hardiness zone 7a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Harper County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Feb 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 19 — 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.
When does frost risk typically end in Harper County?
The last hard freeze (28°F) in Harper County typically lands around Mar 8, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
How long is the growing season in Harper County?
Measured between 28°F hard freezes, Harper County sees about 256 frost-free days — roughly Mar 8 through Nov 19, per NOAA 1991–2020 climate normals. Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
What vegetables grow in Harper County?
Harper County's zone 7a supports a wide range — strong performers include Pecan, Tomato, Okra, Redbud, and Blackberry. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Harper County, really?
Officially, Harper County sits in USDA zone 7a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Harper County?
The federal record around Harper County shows 169 documented sites — 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.
Just moved to Harper County — what should I know before planting?
Start with three facts. Harper County sits in USDA zone 7a, which sets what survives winter; the last 28°F hard freeze typically clears around Mar 8, with about 256 frost-free days to work with (NOAA 1991–2020 climate normals); and 169 documented sites sit on the federal record — a typical footprint for a growing area, worth a look on the contamination map before food beds. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Harper County average. Your yard writes its own version — 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.