Seed Starting Calendar for Oklahoma

Q: When is the last frost in Oklahoma?

It depends on the station. The earliest median last spring freeze in Oklahoma is March 15 at Ardmore; the latest is April 26 at Boise City 2 E. A median is a coin flip: at Oklahoma City the last 32°F freeze comes after April 4 in half of years, and has passed by April 20 in 9 of 10 years (NOAA 1991 to 2020 normals).

Q: When can I plant tomatoes outside in Oklahoma?

UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Oklahoma City is Apr 11 to Apr 18 in 2027. Tomatoes are frost tender, so the date to watch is April 20, when 9 of 10 springs at Oklahoma City have had their last 32°F night. Hardening off starts two weeks before setting out (Mar 28 to Apr 11).

Q: Where do the seed starting weeks for Oklahoma come from?

UNH Cooperative Extension's method works in any state with a spring frost: "Using a calendar, mark the date and count backwards the number of weeks the seed takes to grow from sowing. This will be the date you will start your seeds." The weeks for each crop come from UNH and Colorado State, and the frost date comes from the NOAA station nearest you in Oklahoma.

Q: How many weeks before the last frost do I start peppers and eggplant?

UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Oklahoma City that is Feb 7 to Feb 21 for peppers.

Q: How long do seedlings need to harden off?

About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.

Median last frost from Mar 24 to Apr 18 across Oklahoma

NOAA stations

180

Median last frost, Oklahoma City

Apr 4

Passed in 9 of 10 years

Apr 20

Last frost

Last spring frost dates in Oklahoma

Altus in the southwest reaches its median last frost around Mar 26, Tulsa around Mar 31, Oklahoma City around Apr 4, and Gage and Guymon in the northwest and Panhandle around Apr 17 to Apr 18.

Three dates per station from the NOAA 1991 to 2020 normals. The median is the date half of springs run past. The last column is the date the last 32°F night has passed by in 9 years out of 10, the one to hold tender transplants for.

Station	Elevation	Early (1 in 10 years later than this)	Median last frost	Passed in 9 of 10 years	Median first fall frost
Altus AFBAltus AFB, USW00003981	1,267 ft	Mar 8	Mar 26	Apr 14	Nov 10
TulsaTulsa Intl Airport, USW00013968	650 ft	Mar 11	Mar 31	Apr 15	Nov 4
Oklahoma CityOklahoma City Will Rogers Airport, USW00013967	1,285 ft	Mar 16	Apr 4	Apr 20	Nov 2
Gage AirportGage Airport, USW00013975	2,191 ft	Apr 1	Apr 17	May 2	Oct 20
GuymonGuymon Municipal Airport, USW00003030	3,123 ft	Apr 4	Apr 18	May 1	Oct 23

Crop chart

When to start seeds in Oklahoma, spring 2027

Counted back from the median last frost at Oklahoma City, April 4. Pick another station to redraw the chart for it.

Start indoorsHarden offSet outSow outdoorsMedian last frostLast freeze passed in 9 of 10 years

Every crop, counted from a median last frost of April 4
Crop	Start indoors	Set out	Sow outdoors	Frost class
Tomato	Feb 14 to Feb 28	Apr 11 to Apr 18		Tender, very tender
Pepper	Feb 7 to Feb 21	Apr 18 to Apr 25		Tender, very tender
Eggplant	Feb 7 to Feb 21	Apr 18 to Apr 25		Tender, very tender
Basil	Feb 21 to Mar 7	Apr 18 to Apr 25		Tender
Celery	Jan 10 to Jan 24	Apr 4 to Apr 11		Tender
Cucumber	Mar 14 to Mar 21	Apr 11 to Apr 18	Apr 4 to Apr 11	Tender
Summer squash	Mar 21 to Mar 28	Apr 18 to Apr 25	Apr 4 to Apr 11	Tender
Winter squash	Mar 21 to Mar 28	Apr 18 to Apr 25	Apr 18 to Apr 25	Tender, very tender
Pumpkin	Mar 21 to Mar 28	Apr 18 to Apr 25	Apr 18 to Apr 25	Tender, very tender
Melon (cantaloupe)	Mar 21 to Mar 28	Apr 18 to Apr 25		Tender, very tender
Watermelon	Mar 14 to Mar 28	Apr 18 to Apr 25		Tender, very tender
Onion (from seed)	Dec 27 to Jan 10	Mar 7 to Mar 14		Hardy
Leek	Dec 27 to Jan 10	Mar 7 to Mar 14		Hardy
Parsley	Jan 3 to Jan 10	Mar 14 to Mar 21		Half-hardy
Broccoli	Jan 24 to Feb 7	Mar 7 to Mar 21		Hardy
Brussels sprouts	Jan 24 to Feb 7	Mar 7 to Mar 21		Hardy
Cabbage	Jan 24 to Feb 7	Mar 7 to Mar 14		Hardy
Cauliflower	Feb 7 to Feb 21	Mar 21 to Mar 28		Half-hardy
Kale	Jan 24 to Feb 7	Mar 7 to Mar 14		Hardy
Lettuce	Jan 31 to Feb 7	Mar 7 to Mar 14		Hardy
Swiss chard	Feb 7 to Feb 21	Mar 21 to Mar 28	Mar 7 to Mar 14	Half-hardy
Spinach	Jan 10 to Jan 24	Feb 21 to Mar 14	Mar 7 to Mar 21	Hardy
Peas			Mar 7 to Mar 21	Hardy
Radish			Mar 7 to Mar 21	Hardy
Carrot			Mar 21 to Apr 4	Half-hardy
Beet			Mar 21 to Apr 4	Half-hardy
Beans			Apr 4 to Apr 11	Tender
Sweet corn			Apr 4 to Apr 11	Tender

Six square pots of dark compost seen from above, each holding a single seedling with two narrow seed leaves — Tomato seedlings at the seed leaf stage, one to a pot. The University of Minnesota Extension holds off on fertilizer until a seedling has several sets of true leaves, then feeds at quarter strength once a week. “Tomato Seedlings (49768696597)” by Amanda Slater from Coventry, West Midlands, UK, CC BY-SA 2.0

Extension guide

What Oklahoma Cooperative Extension Service advises

Oklahoma State University Extension (Oklahoma Cooperative Extension Service) publishes the planting guide Oklahoma gardeners work from, Oklahoma Garden Planning Guide (HLA-6004).

“Hardy types may be planted before last frosts or freezes in the spring and are tolerant of cold weather in late autumn.”

Oklahoma State University Extension (Oklahoma Cooperative Extension Service), on broccoli, quoted exactly.

“Tender plants are injured or may be killed by a light frost but can withstand cool weather, while the very tender are injured by cool weather.”

Oklahoma State University Extension (Oklahoma Cooperative Extension Service), on tomato, quoted exactly.

“For warm season vegetables, the soil temperature at the depth where the seeds are planted should be at least 50 F.”

Oklahoma State University Extension (Oklahoma Cooperative Extension Service), on sweet corn, quoted exactly.

“For cool season vegetables, the soil temperature at the depth where the seeds are planted should be at least 40 F.”

Oklahoma State University Extension (Oklahoma Cooperative Extension Service), on peas, quoted exactly.

Planting months

Oklahoma State University Extension (Oklahoma Cooperative Extension Service) planting months for Oklahoma

The extension also publishes planting months by region. Each filled cell is a month the guide gives for planting that crop.

Oklahoma (statewide, southeast earliest to northwest latest)

Crop	Feb	Mar	Apr	May
tomato			Apr
pepper			Apr
eggplant			Apr
broccoli		Mar
cabbage	Feb	Mar
cauliflower	Feb	Mar
lettuce, leaf	Feb	Mar
onion	Feb	Mar
peas, green	Feb	Mar
spinach	Feb	Mar
carrot	Feb	Mar
cucumber			Apr
squash, summer			Apr
cantaloupe				May
beans, green or wax			Apr
sweet corn		Mar	Apr

Planting months from Oklahoma State University Extension (Oklahoma Cooperative Extension Service), Oklahoma Garden Planning Guide, read 2026-09-21. Tomatoes in Oklahoma: April.

A gardener kneeling beside a raised bed setting a young tomato plant into dark soil, an empty nursery pot beside her — Setting out a tomato in June at a community garden. Tender crops go out after the last frost, and after a week or two of hardening off outdoors. “Volunteer planting heirloom tomato (4704185147)”, Pacific Southwest Region 5, Public domain

Seed starting questions for Oklahoma

When should I start seeds indoors in Oklahoma?

Count back from the median last frost where you garden. At Oklahoma City (Oklahoma City Will Rogers Airport) that date is April 4, so for spring 2027 onions start indoors Dec 27 to Jan 10, peppers Feb 7 to Feb 21 and tomatoes Feb 14 to Feb 28. Across Oklahoma's 180 NOAA stations the median last frost runs from Mar 24 to Apr 18 for the middle 90 percent, so a garden near Boise City 2 E starts later than one near Ardmore.

When is the last frost in Oklahoma?

When can I plant tomatoes outside in Oklahoma?

What months do I plant vegetables in Oklahoma?

Where do the seed starting weeks for Oklahoma come from?

How many weeks before the last frost do I start peppers and eggplant?

How long do seedlings need to harden off?

Why do seed starting dates differ across Oklahoma?

Frost dates from NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1). Planting guidance from Oklahoma State University Extension (Oklahoma Cooperative Extension Service), quoted exactly. Seed starting weeks from UNH Cooperative Extension. Compiled 2026-09-21.

First frost in OklahomaThe other end of the season: when fall frost ends the tender crops.Soil temperatureBeans, corn and squash sown direct wait on warm soil as well as the last frost.Oklahoma lawn care calendarSpring seeding, feeding and mowing dates on the same climate.Fall planting calendarGarlic, cool season crops and a second sowing window in the fall.Frost dates by ZIPFirst and last frost odds for any address.