Sow Asian greens in Ohio twice a year: from late March to mid-April, once the soil can be worked, and again from late July to early September. Summer sowings tend to bolt, so the two cool windows do the work. Frost dates set the edges of each window, and the type of green decides where you land inside it. Quick baby leaf types are flexible, while slow napa cabbage is not.
The short answer for Ohio
Sow quick types such as mizuna, tatsoi and baby bok choy as early as late March, and sow again from mid-August into early September. Sow napa cabbage and full-size bok choy in the late-summer window, with napa going in first. Fall sowings usually give the better crop because the plants mature as days shorten and nights cool.
The frost dates behind this come from the zone 6a reference in the Ohio State University Extension Ohio Gardening Calendar. The average last spring frost falls between May 5 and May 15. The average first fall frost falls between October 5 and October 15, which leaves roughly five months between them. These are averages of when freezing weather has historically ended and begun. They describe odds. In about half of years a frost still arrives after the spring date, and in about half it arrives before the fall date.
When can you sow Asian greens in spring?
Seedlings of mizuna, tatsoi and mustard greens shrug off light frost, so there is no reason to wait for May 5 to 15. Sow as soon as a handful of soil crumbles instead of smearing. Stop sowing the larger types by about mid-April. After that, warm weather and lengthening days arrive fast and push plants to send up flower stalks. A long cold stretch right after germination can also trigger bolting in bok choy, so a row cover over early sowings is cheap insurance.
When should you sow Asian greens for fall?
Count backward from October 5. Packet days for these direct-sown crops run from sowing, not from transplanting. Plants that are still growing when frost arrives can finish under a light cover, but they will not size up much in November.
| Type | Spring sowing | Fall sowing | Typical days from sowing |
|---|---|---|---|
| Baby leaf (mizuna, tatsoi, mustard) | Late March to mid-April | Mid-August to early September | About 25 to 40 |
| Bok choy, full size | Early to mid-April | Early to mid-August | About 45 to 60 |
| Napa cabbage | Risky, bolts easily | Late July to early August | About 60 to 80 |
Individual varieties differ, so check the packet. The Best Asian Greens for Ohio sorts them by speed and bolt resistance.
What will not work here
Sowing bok choy or napa cabbage in June or early July fails most often. Warm days and long daylight tell these plants to flower, and they bolt before they size up. Flea beetles and cabbage worms are also at their busiest through summer, so the few plants that do hold on end up shot full of holes.
Napa sown after mid-August will not head. With 60 to 80 days to maturity and the first fall frost averaging October 5 to 15, a mid-August sowing runs out of season before the head fills. Leaves are fine to eat, but there is no tight head. Sow a baby-leaf mizuna instead.
Counting on winter survival in an open bed also fails. The mean daily minimum of the coldest month is 22.0°F at the Columbus reference station (NOAA 1991-2020 normals). Because that is an average, many nights run colder. Most Asian greens die at those temperatures. Tatsoi and mizuna are the hardiest and can come through under a row cover or in a cold frame, but treat that as a bonus and not a plan.
Heavy clay, common across much of the state, causes its own failures. Seed sown in cold, saturated March soil can rot before it sprouts. Sow when the soil crumbles, or build a raised bed that drains faster.
Ohio summers are humid, and humidity punishes tight spacing. Bok choy packed into a solid carpet holds moisture in the crowns, and rot and slugs follow. Thin full-size bok choy to about 6 to 8 inches apart, and give napa more room than that. Baby-leaf rows can stay dense, because you cut them young and the leaves dry quickly.
What changes across Ohio
Ohio is not one garden. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) places the state in zones 5b through 6b. That spans one full zone, or about 10°F in the average annual extreme minimum temperature. There is no single answer for the whole state, and the dates above come from the 6a reference, which sits in the middle of that spread.
What should northern gardeners shift?
In the colder parts of the state, including the northern tier and higher ground, spring warms later and fall frost arrives sooner. Start spring sowing a little later than late March. The bigger change is in fall: count back from an earlier frost date, so napa and full-size bok choy go in earlier than the table suggests. Near Lake Erie, the lake slows spring warming but can stretch the fall season, so gardeners there should check local frost records before assuming the shorter season.
What should southern gardeners shift?
Along the Ohio River and in the warmer south, spring starts sooner and fall frost comes later. That gives you a longer fall window, so you can sow napa and bok choy later in August than the table shows. Warm weather also arrives earlier in spring there, so bolting cuts the spring crop short and the early sowings matter more.
The zone number reflects winter cold, so it tells you which direction to shift but not by how many days. To find your own zone, look up your ZIP code on the USDA map. Then confirm local frost dates with your county extension office.
Where to check this for your own county
Ohio State University Extension runs county offices across the state, and they are the best next stop. A county recommendation beats a state one. The dates in this article are statewide averages, and a county office knows the local soil, the lake or river influence, and the frost pockets in your area.
Look for three things when you get there:
- A local planting calendar with spring and fall vegetable sowing dates for your county or nearby
- Vegetable varieties that have been trialled in your county, especially bolt-resistant bok choy and napa
- Pest timing, such as when flea beetles and cabbage worms peak locally
Extension staff and Master Gardener volunteers often answer these questions by phone or email. If you want the full crop picture, Growing Asian Greens in Ohio covers soil, spacing and pests beyond timing.
Checking this against your own garden
What you see in your own beds outranks every date here. Three observations help you adjust.
Soil warmth by feel. In spring, squeeze a handful from a few inches down. If it crumbles and feels cool but not cold on your bare hand, it is ready for hardy greens. A bed against a south wall will pass this test days before an open, shaded one. Note which bed wins each year.
The first true leaves. Seedlings first show two rounded seed leaves, then the first true leaves with the plant’s real shape. If that takes much longer than you would expect, the soil is cold or the spot is too shaded. If seedlings stall at that stage, the bed is slower than your neighbor’s.
Where frost lingers. On cold mornings in spring and fall, look at where frost sits longest on the lawn. Low corners and spots away from the house stay white later, which tells you where your last spring frost comes late and your first fall frost comes early. Sow early crops in the warmer spots and fall crops where frost lingers least.
Keep a few notes each year. After a season or two, your own record will be a better calendar than any average.
Common questions
Can you sow Asian greens in Ohio in summer?
Mostly no. Heat and long days push bok choy and napa to bolt, and pests peak. Quick baby-leaf types sown in light shade can work, but the better move is to wait until late July for fall sowings.
Can Asian greens go in the ground before the last frost?
Yes. Mizuna, tatsoi and mustard seedlings handle light frost, so late March sowing works once the soil is workable. Cover bok choy with a row cover if a hard freeze is forecast.
Do Asian greens survive Ohio winters?
Rarely, in an open bed. With a coldest-month average low of 22.0°F at the Columbus reference station, most die. Tatsoi and mizuna can survive under a row cover or in a cold frame.
How late can I sow bok choy for fall?
Count back from the first fall frost, which averages October 5 to 15 at the 6a reference. Full-size bok choy takes about 45 to 60 days from sowing, so early to mid-August is the limit. Baby bok choy can go in a little later.