Asian greens grow best in Oklahoma in two windows: early spring, as soon as the soil can be worked, and fall, once the summer heat breaks. At the Oklahoma City reference station, the last spring frost falls between March 28 and April 10, and the first fall frost between October 29 and November 8. Fall is the more dependable season. Spring sowings race the heat, and the heat usually wins.
When the soil is warm enough in Oklahoma
Most gardeners start with the last spring frost. At the Oklahoma City airport station, NOAA’s 1991-2020 U.S. Climate Normals place it between March 28 and April 10, the 30-70% probability band for a 32 F freeze. A freeze after April 10 can still happen in any given year. Suburban and rural gardens typically see the last spring frost one to two weeks later than the airport, and more at elevation, so check your own county’s dates before you mark a calendar.
The frost date stands in for what the seeds actually need, which is soil that has shaken off winter. The ground lags the air. It keeps warming for weeks after the frost risk ends, so a bed can be frost-free and still cold and sodden. Asian greens sown into that kind of soil sit and sprout unevenly.
How do you tell the soil is ready to sow?
Squeeze a handful from the top few inches. If it crumbles instead of forming a wet clump, the bed is workable. A soil thermometer pushed in at seed depth in the morning gives a better answer than the air temperature. Ask Oklahoma State University Extension for the soil temperature range that suits each type, since it differs between a quick baby-leaf mustard and a heading napa cabbage.
Spring has a catch in central Oklahoma. Once the soil is ready, the clock is already running, because lengthening days and rising heat push these plants toward flowering. Early sowings of fast types make sense. Anything that needs a long, steady run to size up belongs to fall.
When should you sow Asian greens in fall?
Work backward from the first fall frost, which the reference station puts between October 29 and November 8. Rural and suburban gardens often see it a week or two sooner. Read the days to maturity on the seed packet, which count from sowing for direct-sown greens. Then add a margin, because growth slows as days shorten and nights cool. A plant that is only half grown when hard freezes arrive will stall, so the margin matters more than the packet number.
Late summer soil is the opposite problem from spring soil. It can be too hot for good sprouting. Shade the seedbed with a light cloth, water the row daily until seedlings are up, and sow when the worst of the heat eases rather than on a fixed calendar day. These crops are brassicas, relatives of cabbage, kale and mustard, so avoid putting them where those crops grew last season.
How long the season lasts here
The reference station has about 202 to 225 days between the mean last spring frost and the mean first fall frost. That is a long run by national standards, and it is long enough to allow a second sowing of nearly everything in this family. Gardeners in colder states get one shot and have to make it count. Oklahoma growers get two, and the second is often the better one.
The frost-free span is not all usable, though. Summer sits in the middle and cuts it into two cool windows with a hot gap between them. Spring sowings run from workable soil until the heat arrives. Fall sowings run from the first easing of summer until a hard freeze. Treat them as separate crops with separate calendars.
Is succession sowing worth it in Oklahoma?
Yes, especially in spring. Instead of one large sowing that bolts all at once, sow a short row every couple of weeks while the weather is still mild, and stop when the days turn hot. In fall, repeat the pattern in the other direction, with the last sowing timed so that plants can finish before the first frost. The succession approach pairs well with the general advice in Growing Asian Greens: Fast, Cold-Hardy, and Prone to Bolting, which covers why these plants run to seed when stressed.
The long window also relaxes the transplant question. Direct sowing is simpler for most types, and it avoids the root disturbance that can push a plant to bolt. If you do buy or start transplants, pick young ones and check the roots before planting. White, loose roots are what you want. A tight, circling mass means the plant is already stressed, and it will likely flower early. Remember that suburban and rural gardens run a week or two shorter at both ends than the airport figures, so trim the window accordingly.
Heat and water in Oklahoma
Summers here are long and hot, and rain tends to arrive in heavy bursts with dry stretches between. For Asian greens, that pattern shapes the whole year. This family belongs to the second half of it. Spring crops are a bonus, and the main crop goes in once the heat relents. Two facts govern how well that works: how late a sowing can still finish before the first frost, and how cold the winter gets.
What does summer heat do to Asian greens?
Heat is what sends them to seed. A plant that sits through hot weather turns bitter, throws up a flower stalk, and is done. Shade over the bed in the afternoon, mulch to keep the roots cool, and enough space between plants for air to move all reduce the stress. Uneven watering makes it worse. Dry spells followed by soaking storms leave leaves tough and prone to tip burn, so steady, deep watering beats frequent light sprinkling. Humid spells also invite leaf spots and mildew, which is another reason to give plants room.
Pests follow the same calendar. Flea beetles chew small holes in young leaves in warm weather, and caterpillars arrive on cabbage family plants through the growing season. Floating row cover set at sowing and hand-picking keep both in check without sprays. Because Asian greens are brassicas, they share these problems with cabbage, kale and mustard, and rotation only works if the next crop goes in a bed that has been free of that whole family. Turnips and rutabagas count as part of it too.
Will Asian greens survive an Oklahoma winter?
Some will, under cover. The mean daily minimum of the coldest month at Oklahoma City is 27.0 F, which means a typical winter night dips below freezing. USDA’s 2023 Plant Hardiness Zone Map, which is based on the average annual extreme minimum, puts the state at 6a to 8a, so the cold varies by region, with the northern and panhandle areas colder than the southeast.
The hardiest types, such as tatsoi and the leafy mustards, can stand through much of that cold if you add a row cover or low tunnel over the bed. Tender types, including most heading napa cabbages, tend to end with the first hard freeze. Row covers buy a few degrees, not a different climate. Readers in other parts of the South can compare notes with Growing Asian Greens in Georgia and Growing Asian Greens in North Carolina, where the heat and winter mix differ from Oklahoma’s.
Which Asian greens suit Oklahoma
Choose by type first. Oklahoma’s long, hot summer and its cold snaps mean the best picks are fast types for the spring window, heat-tolerant or slow-bolting types for the shoulder seasons, and cold-hardy types for fall and winter. In the wetter, more humid parts of the state, disease resistance becomes the first thing to read on the seed packet.
| Type | Best slot | What to watch |
|---|---|---|
| Tatsoi and mizuna | Early spring and fall; overwinter under cover | Bolt in heat, so sow early |
| Leafy mustard greens | Fall and winter under cover | Turn sharp in warm weather |
| Pak choi (bok choy) | Fall; short spring window | Bolts if stressed or if transplants are root-bound |
| Choy sum | Early spring and early fall | Needs steady moisture |
| Napa cabbage | Early fall only | Needs the longest run; hard freeze ends it |
A short window favors the earliest, quickest types, which is why baby-leaf mustards and mizuna do well in spring. A hot one favors plants given afternoon shade and cool roots. A humid one favors plants with listed disease resistance and enough spacing for air to move between leaves.
Specific variety names are left out on purpose. The varieties that have been trialled in Oklahoma conditions are the only recommendation that carries weight, because performance shifts with soil, rainfall and elevation from the Panhandle to the southeast. Any name offered without that local testing would be a guess. Oklahoma State University Extension and your county office can tell you what has worked in gardens near you, including which types hold up against bolting and leaf disease. Call before you buy seed, since the packet rarely answers that question.
Common questions
When is the best time to plant Asian greens in Oklahoma?
Fall gives the most reliable crop, sown once the summer heat eases and early enough to finish before the first frost, which falls between October 29 and November 8 at the Oklahoma City station. A second, shorter window opens in spring once the soil is workable, after the March 28 to April 10 last frost band for the same station.
Do the frost dates apply to my garden?
They describe the Oklahoma City airport station. Suburban and rural gardens usually see the last spring frost later and the first fall frost earlier, often by one to two weeks, and more at higher elevation. Use them as a starting point and confirm with your county extension office.
Can I grow Asian greens through an Oklahoma winter?
The hardiest types can, with a row cover or low tunnel. The coldest month’s mean daily minimum is 27.0 F at Oklahoma City, and a hard freeze can still end tender types. Zones range from 6a to 8a, so colder parts of the state need more protection.
Which variety should I plant?
Pick the type that fits your season, then ask Oklahoma State University Extension which varieties have been trialled locally. Look for slow-bolting and disease-resistant notes on the packet. Rotate away from beds that held cabbage, kale, mustard, turnips or rutabagas, since they share the same pests and diseases.