The Best Asian Greens for Wisconsin

Quick-growing leaf types do best in Wisconsin: mizuna, tatsoi, komatsuna, baby bok choy and mustard greens. They finish before summer heat triggers bolting, and they shrug off the light frosts that come in both April and October. Heading napa cabbage and full-size bok choy also grow well, but mostly as a fall crop. Chinese broccoli types (gai lan, choy sum) fit in either season.

The short answer for Wisconsin

Choose by type, and let the calendar decide the season. At the reference station, the last spring freeze (32°F) falls between April 16 and April 29, and the first fall freeze falls between October 17 and October 29. Those dates mark the band where the chance of a freeze is between 30 and 70 percent. They are the middle of the odds. A freeze can still come earlier in fall or later in spring, so treat them as a window, not a deadline.

Asian greens are cool-season crops. Most of them germinate in cold soil and take a light frost without damage. What stops them is long, hot days, which push the plant to send up a flower stalk. Wisconsin has a generous cool window on both sides of summer, so the best varieties are the ones that fit inside it.

Which Asian greens work best in a spring planting?

Pick the fastest types. Mizuna, tatsoi, komatsuna, mustard greens and baby bok choy can go in as soon as the soil is workable, ahead of the spring freeze band. Packet times vary for baby leaves and for full size, counted from sowing. That puts harvest in May and early June, ahead of the heat.

Which are best for fall?

Fall is the better season for the slower, bigger types. Days shorten and nights cool, so napa cabbage, full-size bok choy and gai lan have little reason to bolt. Sow them so they mature before the freeze band. Our guide on when to sow Asian greens in Wisconsin gives the sowing windows in detail.

For a first garden, start with mizuna and tatsoi. They forgive uneven timing, and you can cut them young and let them regrow. For more on the basics, see Growing Asian Greens in Wisconsin.

What will not work here

Why do summer sowings of Asian greens fail?

Bok choy, mizuna and napa sown in June or early July mostly bolt before they size up. Daylight lengthens around the solstice, and the plants read that as a signal to flower. The result is bitter, tough leaves on a stalk. If you want greens in midsummer, grow something that likes the heat, such as amaranth or water spinach, and save the cool-season types for the shoulders.

Spring-planted heading napa cabbage fails for the same reason. It needs weeks of cool weather to build a tight head, and spring in Wisconsin warms fast. A planting that starts well in April can bolt by June.

What about slow types and late plantings?

The fall freeze sets a hard stop. With the first freeze between October 17 and October 29 at the reference station, and earlier inland and in the north, a heading napa sown in mid-August is racing the weather. Chinese broccoli started after midsummer runs into the same wall. A light freeze will not kill most of these, but a hard one will wreck a head that has not finished filling.

Wintering over outdoors does not work either. The mean daily minimum of the coldest month is 17.2°F (Milwaukee), and that is an average night, not the worst one. Most Asian greens tolerate cold dips with a little cover, but weeks of hard cold will kill them. A low tunnel can stretch the season. It will not carry them through January.

Humid spells make crowding a problem. Closely spaced bok choy holds moisture at the base of the leaves, which invites rot and downy mildew in a wet August or September. Give full-size plants room, spaced apart depending on the variety. Slugs love the same damp, shaded crowns.

Flea beetles are the spring problem. They pepper the leaves of mizuna, tatsoi and mustard with tiny holes. Floating row cover over the bed from sowing onward keeps them off, and it also adds some frost protection.

What changes across Wisconsin

Wisconsin is not one garden. The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places the state anywhere from zone 3b to zone 6a. That is several zones of spread, so no single answer fits the whole state. Zone is built on the average annual extreme minimum temperature, so it says more about perennials than about a leaf crop sown in April. For greens, frost dates matter more. Use the zone map to find your own zone rather than guessing from a neighbor’s.

The frost dates above come from one reference station. Lake Michigan delays the first fall freeze at the lakeshore, which gives shoreline gardens extra weeks for a fall crop. Inland southern Wisconsin typically freezes in early October, and the north freezes far earlier. A gardener near Lake Superior or in the northern woods has a much shorter fall window than one in Racine.

The adjustment is simple. In the north, sow the fall crop weeks earlier than the southern schedule suggests, favor the fast types (mizuna, tatsoi, baby bok choy), and plan on row cover. Spring sowings start later there because soil thaws later. Leave out full-size napa unless you can protect it. Along the lake, the fall crop can run later, and napa becomes a more reasonable bet.

Where to check this for your own county

A county recommendation beats a state one. The advice for the whole state is a starting point, and the best source for local detail is University of Wisconsin Extension, which has an office in nearly every county.

Look for two things. The first is a local vegetable planting calendar, ideally one built from frost dates for a station near you rather than for the state as a whole. The second is a list of varieties that horticulture staff or Master Gardener volunteers have grown in your county. A variety that held up through a wet fall in one county may not suit another.

When you call or visit, ask which Asian greens people in your area grow successfully, when the first fall freeze usually arrives where you live, and which pests are active. Staff can also tell you about local conditions that rarely make it into state guides, such as heavy clay, sandy soils or a persistent frost pocket.

Checking this against your own garden

Your own observations outrank every date here. Three are worth watching, and none needs a gadget.

• Soil by feel. Squeeze a handful in early spring. If it crumbles instead of staying in a wet clump, and it no longer feels icy, greens can go in. Beds that reach this stage first are your warm, well-drained spots.
• First true leaves. After the seed leaves, the first true leaves signal that seedlings have settled in. If they come slowly, the bed is cold. If your earliest sowing bolts, that bed gets too much heat or light for spring.
• First blackened leaves. Note which tender plants, such as basil or squash, get hit first in fall. That shows where cold air pools, and you can place a fall crop elsewhere or cover it.

Keep notes for a season or two. They will tell you more about your yard than any statewide table.

Common questions

Can I grow bok choy all summer in Wisconsin?

Not reliably. Long days and heat push it to bolt. Grow it in spring and again in late summer for fall, and use heat-tolerant greens in between.

Do Asian greens survive a Wisconsin winter?

Generally no. The coldest month averages a daily low of 17.2°F, which is too cold for most unprotected plants. A low tunnel extends the harvest a few weeks into late fall.

Is spring or fall better for Asian greens?

Fall is usually better, especially for napa and full-size bok choy. Spring suits the fastest leaf types, which can finish before the heat arrives.

Which Asian green is easiest for beginners?

Mizuna and tatsoi. They grow fast, tolerate light frost and can be cut young for salads or cooking. Cover them in spring to keep flea beetles off.