Asian greens go in the ground twice in New Jersey: once in early spring, then again from midsummer into early fall. Fall is the stronger season. Bok choy, mizuna, tatsoi and their relatives want cool soil and moderate day length, and September and October offer a longer stretch of both than the weeks between thaw and late-spring heat. Dates for each type follow below.
The short answer for New Jersey
Sow in early March, as soon as the soil can be worked, and stop by mid-April. Sow again from late July (napa cabbage) to mid-September (quick baby leaves). Those dates come from frost odds at Newark’s airport weather station. NOAA’s 1991-2020 U.S. Climate Normals put the last spring freeze between March 29 and April 6, and the first fall freeze between November 4 and November 16.
Each of those dates is a probability of a 32°F freeze, drawn from the band where the odds sit between 30 and 70 percent. A freeze can still arrive outside that band. They also describe one reference city. Suburban and rural gardens typically see the last spring frost later and the first fall frost earlier, often by one to two weeks, and more at elevation.
When do you sow Asian greens in spring in New Jersey?
Seedlings of bok choy, mizuna, tatsoi and komatsuna shrug off light frost, so the sowing can start before the reference last-frost dates. Gardens farther from the city should wait a week or two longer. A square of floating row cover handles the odd 28°F night.
The window closes in mid-April. Days lengthen quickly after that, and Asian greens respond to long days and warm weather by sending up flower stalks. Choose bolt-resistant selections for spring, and The Best Asian Greens for New Jersey sorts them by type.
When do you sow Asian greens in fall in New Jersey?
Work backward from the first fall freeze. A direct-sown bok choy needs time from sowing to a full head, baby leaves less, and napa cabbage longer still. Growth also slows as days shorten, so leave a cushion.
| Type | Spring sowing | Fall sowing |
|---|---|---|
| Baby leaves (mizuna, tatsoi, komatsuna) | Early March to mid-April | Mid-August to mid-September |
| Bok choy and pak choi | Early March to early April | Mid-August to early September |
| Mustard greens | Early March to early April | Mid-August to mid-September |
| Napa cabbage | Skip it, it bolts | Late July to mid-August |
Treat the dates as a starting point for a station-city garden and move them later in spring and earlier in fall for colder sites.
What will not work here
Spring napa cabbage is the classic failure. Napa needs time to form a head, and a March sowing finishes right as the days get long and the weather warms. The plants bolt before the head tightens. Napa belongs in the fall calendar only.
Midsummer sowing in an open bed is the second trap. Soil in July and early August runs hot, and seedlings come up thin and stressed. Flea beetles, which chew small holes in the leaves of young brassicas, tend to be at their worst in warm weather. Sowing quick types a few weeks later, from mid-August, avoids most of that. If July sowing is a must, put the bed in afternoon shade and keep the seed row evenly damp until it sprouts.
Close spacing fails in humid weather. New Jersey summers are humid, and early September can still bring muggy stretches. Full-size bok choy crowded too closely stays wet in the center, which invites leaf spot and slugs. Give heading types room and save tight rows for baby leaves, which are cut young, before the canopy closes.
Weekly watering fails too. Asian greens are shallow-rooted, and a late-summer seedbed can dry out in a couple of days. Light, frequent watering until sprouting works better than one weekly soak. After that, steady watering, delivered when rain falls short, keeps growth steady.
Waiting too long in fall is the quiet mistake. A sowing at the end of September or in October may sprout fine, but the plants stall at seedling size as nights cool and days shorten. Then the frosts of early November arrive. In rural gardens, where the first freeze can come one to two weeks ahead of the reference dates, those plants never reach harvest.
Winter itself ends the season for most types. The mean daily minimum in the coldest month at the reference station is 25.5°F, an average night. Individual nights go colder. Bok choy and napa will not carry through January in an open bed. Tatsoi and mizuna tolerate more, and a low tunnel can stretch the harvest into winter, but plan on the main crop finishing around the first hard freeze.
What changes across New Jersey
There is no single answer for the state. The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places New Jersey in zones 6a through 7b. That system rests on one variable, the average annual extreme minimum temperature. The colder end of that range sits in the northwest highlands and at elevation, and the milder end toward the coast and the south.
The dated windows in this article come from the reference city, so a reader in the colder zones should shift them. Start spring sowing a week or two later, since frozen or sodden soil holds on longer. Start fall sowing a week or two earlier, since the first hard freeze arrives sooner. A garden at elevation in the north may gain only a short stretch of harvest at each end compared with the figures above.
Gardens near the shore often hold frost off longer in fall, so late-September sowings of baby leaves have a better chance there. Low spots matter at any latitude. Cold air drains downhill and pools, so a bed at the bottom of a slope can frost while the one on the rise stays clear.
Hardiness zone and frost dates answer different questions. The zone describes winter extremes and helps with plants meant to overwinter. Frost dates decide when the season opens and closes, which is what a sowing calendar depends on. Two gardens in the same zone can differ by weeks in frost timing.
To find your own zone, look up your location on the USDA Plant Hardiness Zone Map and read it yourself. For the full range of crops that suit your conditions, see Growing Asian Greens in New Jersey.
Where to check this for your own county
Start with Rutgers NJAES, the state’s land-grant extension service. Each county has an office, and the staff and Master Gardener volunteers there know local conditions in a way no statewide calendar can.
Look for two things. One is the local vegetable planting calendar for your county, which lists spring and fall windows for cool-season crops. The other is the varieties trialled nearby, since a bok choy that holds through a muggy September in the south may not suit a northern ridge. If Asian greens are not named in a calendar, use the dates for cabbage, broccoli and kale. All of them are cool-season brassicas and follow much the same timing.
Ask the county office about pest timing as well. Flea beetles in spring and cabbageworms in early fall come on a local schedule that affects whether row cover is needed and when.
A county recommendation beats a state one. A statewide calendar averages places that differ by weeks in frost dates and by several hardiness zones. It gives a sensible starting point and a county office refines it. Where the county advice and the dates above disagree, follow the county.
Checking this against your own garden
Your own ground outranks every date here. Three things are worth watching, and none needs equipment.
- Soil warmth by feel. Push a bare hand a few inches into the bed in early spring. If it feels cold and clammy and the soil clumps in a wet ball, wait. Crumbly, workable soil that no longer chills your fingers is ready for the first sowing. A bed that reaches that point a week before its neighbor, usually one facing south, is the one to sow first.
- Local bloom. Forsythia flowering in your neighborhood has long been a rough cue for cool-season crops. If it blooms two weeks later in your yard than in town, that gap is your microclimate and you should shift your sowing by about the same amount.
- First true leaves. Seedlings first show two rounded seed leaves, then the first true leaves with the shape of the mature plant. Seedlings that stretch tall and leggy before true leaves appear were sown into warmth or too little light. Seedlings that stay small and pale are probably cold. Compare a few sowings a week apart and keep the one that grew sturdiest.
Frost watching adds a fourth check in fall. The first white lawn in your yard, and where it appears first, shows where cold air collects and which beds hold on longest.
Common questions
Can I sow bok choy in July in New Jersey?
It is possible only in afternoon shade with the seedbed kept damp until sprouting. Bok choy sown in hot soil often bolts or gets chewed by flea beetles. Waiting until mid-August gives better results, and napa cabbage is the exception, since it needs a late-July start to finish before frost.
Do I need to start Asian greens indoors?
No. These greens grow quickly from seed sown directly in the bed, and they dislike root disturbance. Indoor starts only make sense for early spring heads when the soil is still frozen, and even then transplants should go out while still small.
Will Asian greens survive a New Jersey winter?
Most will not in an open bed. The coldest month averages a nightly low of 25.5°F at the reference station, and individual nights run colder. Tatsoi and mizuna take more cold than bok choy or napa, and a low tunnel or row cover extends the harvest, but plan on harvesting before the first hard freeze.
How late can I sow in fall?
For baby leaves in an open bed, watch the forecast at the reference city, and earlier for colder sites. Under row cover or a low tunnel, a sowing into early October may still produce small cuttings. Anything sown later stalls as the days shorten.