Sulphur, Oklahoma, sits in USDA hardiness zone 7b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Among the crops suited to this profile: cabbage, prickly pear, california poppy, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Sulphur, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Sulphur lot. 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 Sulphur — soil, climate, flood, and parcel records. How we handle your address.
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Sulphur — the short answer
Sulphur, Oklahoma: USDA zone 7b, about 238 days between hard freezes, across 4K acres of city.
- USDA zone
- 7b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 11
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~238
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 4K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Sulphur's average, not your lot's — a low corner or a tree line moves it. Against Sulphur's 238-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Sulphur
Each reading below is measured for Sulphur itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSulphur runs about 238 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
MeasuredSulphur 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 Sulphur is in
Sulphur sits in the Cross Timbers — EPA Level III, inside the wider Great Plains. That is read at Sulphur's own centroid rather than borrowed from Murray County.
What Grows in Sulphur
Every plant below cleared Sulphur's own zone 7b and its 238-day season. Each card opens that plant's Oklahoma profile. How we score.
Is it too late to plant in Sulphur?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Feb 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 18 (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. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
What's on the federal record near Sulphur
Closest first, within ~10 miles of Sulphur. Listing isn't leaking, and distance isn't exposure.
- Fillin StationUnderground Storage Tanks · 1800 ft
- SinclairUnderground Storage Tanks · 1900 ft
- O'REILLY AUTO PARTS STORE 287Brownfields · 2000 ft
- Kerr Mcgee #6751Underground Storage Tanks · 2200 ft
- Snak Shak CentralUnderground Storage Tanks · 2200 ft
- Snak Shak WestUnderground Storage Tanks · 2500 ft
- SupermartUnderground Storage Tanks · 2600 ft
- C.M. Mays Lumber CompanyUnderground Storage Tanks · 2600 ft
- Elbert A. Franklin, D.D.SUnderground Storage Tanks · 0.5 mi
- Gulf Service StationUnderground Storage Tanks · 0.6 mi
- Marion Splawn Oil CoUnderground Storage Tanks · 0.6 mi
- Wal-Mart Supercenter #225Underground Storage Tanks · 0.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Sulphur'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 Sulphur.
Total Sites
114
within ~10 miles of Sulphur
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Sulphur
Severity Distribution
within ~10 miles of Sulphur
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Sulphur, CAFO runs higher than the national average — 3 sites within ~10 miles of Sulphur. That's not a problem with your land — it's information about it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check your specific parcel in Sulphur
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 Sulphur average
Your land is one point inside Sulphur
Everything above resolves to Sulphur as a whole — one PHZM band and one 28°F frost record, read across 4K 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 city 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 local average.
Your Lot vs the Sulphur Average
Sulphur Average
- ●USDA Zones 7b, averaged across Sulphur
- ●One soil character for all of Sulphur
- ●Frost dates read at Sulphur's scale: Mar 18 to Nov 11
YOUR Parcel
- ✓Your exact zone, not Sulphur's 7b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Sulphur
Pull a site-specific report for your exact address in Sulphur, Oklahoma — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Sulphur averages can't show:
We read public map data around Sulphur — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sulphur average
How we know this about Sulphur
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Sulphur’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Sulphur
When does frost risk typically end in Sulphur?
The last hard freeze (28°F) in Sulphur typically lands around Mar 18, 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 8.
When is the first frost in Sulphur?
The first hard freeze (28°F) in Sulphur typically arrives around Nov 11, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 28, so the watching starts about Oct 12 — about 238 days after the spring freeze cleared.
How long is the growing season in Sulphur?
Measured between 28°F hard freezes, Sulphur sees about 238 frost-free days — roughly Mar 18 through Nov 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 8 to Oct 28, about 203 days.
Is the soil safe to grow vegetables in Sulphur?
The federal record around Sulphur is a meaningful one — 114 documented sites, mostly Underground Storage Tanks entries (69), the nearest Underground Storage Tanks record about 0.3 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.
How do I protect my plants from frost in Sulphur?
From about Oct 12 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Nov 11 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Nov 11. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Sulphur's scale — its 7b band and its 238-day season. Your yard writes its own version of Sulphur's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Sulphur’s own scale
6 of the readings below were taken at Sulphur's own scale — its own ~238-day season between 28°F freezes, the 3,850 acres it covers and 114 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Sulphur's own USDA hardiness band, zones 7bUSDA PHZM 2023
- Sulphur's own 28°F hard-freeze dates, about Mar 18 and Nov 11 and the ~238-day span between themNOAA 1991–2020 Climate Normals
- 114 documented contamination sites on the federal record near Sulphur, the closest Underground Storage Tanks record about 0.3 miles out from the town centreFederal environmental registers
- Sulphur's boundary and the 3,850 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7b and a ~238-day seasonGrowable Ground crop-matching engine
- The ecoregion at Sulphur's own centroid, the Cross TimbersUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Sulphur's 3,850 acres read through its county's SSURGO summaryfrom Murray County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Murray County
- The growing challenges every Oklahoma grower plans around — written at state scale, so they stay on the state guidefrom Oklahoma
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Murray County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Sulphur's 3,850 acreswhy one lot differs from the next →
- Which side of Sulphur you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 3,850 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.3 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Sulphur-wide figureread your own land →
More in Oklahoma
Wider growing context
What grows across OklahomaSulphur sits outside our named growing regions, so Oklahoma as a whole is its closest context here.
Nearby growing guides