New Jersey gardeners get two windows for Asian greens. One opens in spring as the soil thaws and dries, and a larger one opens in late summer for a fall crop. The fall crop is usually the better bet, because bok choy, mizuna and their relatives bolt when long, warm days arrive. Timing both windows starts with the frost dates and ends with the thermometer in the ground.
When the soil is warm enough in New Jersey
At the airport weather station in Newark, the 32°F freeze probabilities in the NOAA NCEI U.S. Climate Normals 1991-2020 put the last spring frost between March 29 and April 6 (the 30-70% band). That is a statement of odds across thirty years of records, so a late freeze after the band can still happen in any given spring.
Newark is a reference city, and it sits near the coast in a built-up area. Suburban and rural gardens typically see the last spring frost one to two weeks later, and more at elevation, as in the northwest highlands. Check your own county’s dates before you pencil anything onto the calendar.
Why does soil temperature matter more than the frost date?
A frost date tells you when freezing air stops. Seeds respond to the ground, and the soil warms after the frost risk ends, not with it. Spring soil in New Jersey is often cold and saturated for a couple of weeks past the last freeze, especially in clay.
Seed sown into cold, soggy ground sits there. Some of it rots, and some seedlings collapse at the soil line from damping off. A cheap soil thermometer pushed a couple of inches deep in the morning gives a better answer than any calendar. So does a simple squeeze test: a handful of soil that crumbles is ready to work, and one that stays in a wet ball is not.
What does that mean for your first sowing?
In most suburban gardens, the first spring sowing goes in from mid-April once the bed passes the squeeze test. Asian greens tolerate cool weather better than tomatoes or beans, so there is no reason to wait for true warmth. The spring crop is a race, though. As days lengthen and the weather warms, plants shift from leaf to flower stalk. Pick quick types and harvest young. A fuller overview of the family sits in Growing Asian Greens: Fast, Cold-Hardy, and Prone to Bolting.
Flea beetles peppering young leaves with tiny holes are the usual spring welcome. Floating row cover laid over the bed at sowing keeps them off. Bok choy, mizuna, tatsoi, komatsuna and mustard greens are all brassicas, and they share pests and diseases with cabbage, kale and broccoli. Turnips and rutabagas belong to that family too. A bed that grew cabbage last year is not a fresh bed for Asian greens, so follow the crop rotation guide and keep brassicas out of the same soil for a few seasons.
Variety recommendations belong with your local extension service. Rutgers Cooperative Extension can point you to the varieties that have been trialed in New Jersey conditions.
How long the season lasts here
At the airport station, the span between the mean last spring frost and the mean first fall frost runs about 212 to 232 days, with spring frost between March 29 and April 6 and first fall frost between November 4 and November 16. Suburban and rural gardens lose one to two weeks at each end, so count on a shorter window than Newark’s.
Can you sow Asian greens twice in New Jersey?
Yes, and the window is long enough that you could sow three times if you wanted. Greens that finish in a matter of weeks fit easily into a season this size. A spring sowing comes out by early summer, the bed rests or grows something warm-season, and a fall sowing goes in as the heat breaks. The succession sowing guide on this site covers how to stagger plantings so a single weekend of harvest does not bury you in bok choy.
Summer is the gap. Sowing in the hottest weeks works only with shade cloth, mulch and daily watering, and even then seed can fail to come up in hot soil. Most gardeners leave the bed for other crops through July and sow again once the nights begin to cool. That fall sowing is the one that pays off, since slower, cooler growth makes sweeter leaves and fewer bolted plants.
Is transplanting worth the root check?
With a window this long, direct sowing is the easier path for most Asian greens. Transplants earn their place when you want to get a spring crop in earlier than the soil allows, or when a fall sowing needs a head start against late-summer heat in the seedbed. Before you plant any transplant, slide it out of its cell and look at the roots. White, loose roots are fine. A tight brown coil circling the cell means the plant has been held too long, and a root-bound seedling is more likely to bolt once it hits the ground.
The picture changes in the north. Where a growing window is far shorter, as in Growing Asian Greens in Alberta, the first sowing is the only one, and a transplant has to be perfect to be worth the trouble. Gardeners in the cooler northern counties of New Jersey sit closer to the upstate New York situation described in Growing Asian Greens in New York, where fall sowings have less margin.
Heat and water in New Jersey
Summers in the Newark area run hot and humid, and the heat is hard on this family. Asian greens belong to the second half of the year, so the numbers that govern them are the first fall frost and the winter low. Midsummer heat matters mostly as a reason not to depend on a spring sowing. In midsummer, long days plus warm nights push plants to flower within weeks of sowing. Humid weather brings leaf spots and downy mildew on wet foliage, and rainy stretches in late summer favor slugs.
Water is a different story. These are mostly leaf, so the crop needs steady moisture to stay tender, and about an inch a week from rain or hose is a sound target. A seedbed sown in late summer has to stay damp while the soil is still warm. Water in the morning so leaves dry by evening, and mulch the rows to hold moisture and cool the root zone.
How late can you sow Asian greens for fall in New Jersey?
The first fall frost at the Newark airport station falls between November 4 and November 16 (NOAA’s 1991-2020 normals, 30-70% band). Suburban and rural gardens often see it one to two weeks earlier than that. Take the packet’s days to maturity, which count from sowing for direct-sown greens, and count back from your local frost date. Add extra time, because growth slows sharply as days shorten in October. A sowing made now, in the second half of October, will not reach harvest size in the open ground, so plan the next one for August.
Will Asian greens survive a New Jersey winter?
The mean daily minimum of the coldest month at Newark is 25.5°F, from the 1991-2020 normals. The USDA Plant Hardiness Zone Map (2023) places the state in zones 6a to 7b, and that range depends on location. On most winter nights the temperature falls below freezing, which ends tender types such as heading napa cabbage after the first hard freeze.
The hardiest greens, such as tatsoi and mizuna, can stand through a good part of the cold under a low tunnel or heavy row cover. Open ground ends the crop at the first hard freeze, and even covered plants are not guaranteed to come through a deep cold snap. If the leaves turn glassy and collapse after thawing, that planting is done, and you pull it.
Which Asian greens suit New Jersey
The choice comes down to type. New Jersey has a long season, a hot and humid summer, and a fall that ends in a hard freeze. The best-suited greens are fast, loose-leaf types that finish before heat or hard cold arrives, and that stay healthy in damp weather.
What should you look for on a seed packet?
For a spring crop, choose the earliest and fastest types and any marked as slow to bolt. Baby bok choy, mizuna, komatsuna and tatsoi fit the spring window, since they go from seed to cut leaf quickly. For fall, you can add larger bok choy, choy sum and mustard greens, which develop sweetness as nights cool. Heading types such as napa cabbage need cool weather to form a tight head, so they belong in the fall sowing, started in late summer.
Humidity makes disease resistance the first thing to read on a packet. Give plants airflow with generous spacing, thin seedlings early, and water at the base. Shade cloth over a late-summer seedbed and a layer of mulch keep roots cooler in the heat. Because these are brassicas, never follow cabbage, kale or broccoli with them.
Where do you find varieties that work in New Jersey?
A cultivar that does well in a seed catalog photo, or in a Cape May garden, may stall in the cooler highlands or bolt in a hot suburban bed. Only locally trialed varieties tell you much. Rutgers Cooperative Extension and your county office can name the varieties that have been grown and compared in New Jersey, and they can give you a frost date closer to your own ground than Newark’s.
Common questions
When should I plant Asian greens in New Jersey?
Sow a spring crop from mid-April once the soil is workable and crumbles in the hand, and make your main sowing in late summer for fall. Count back from your local first fall frost, since the Newark airport band of November 4 to November 16 is often earlier in suburban and rural gardens.
Do Asian greens bolt in New Jersey summers?
Yes. Hot, humid summers push most of them to flower quickly, especially when sown in spring. Fast types harvested young, plus a fall sowing, avoid most of the trouble.
Can Asian greens stay in the garden over the winter?
The hardiest types can stand under a low tunnel or row cover, though the mean daily minimum of 25.5°F in the coldest month at Newark means open beds usually end at the first hard freeze. A covered crop is not guaranteed, so inspect leaves after each thaw.
Can I plant Asian greens where cabbage grew last year?
Avoid it. Asian greens, turnips and rutabagas are brassicas, and they share soil-borne disease and pests with cabbage, kale and mustard. Rotate to a bed that has been free of brassicas for several seasons, and consult the extension service for how long to wait in your area.