Fast, cold-tolerant leaf types suit New Jersey best: mizuna, tatsoi, komatsuna, mustard greens and baby bok choy. Sown in early spring or, better, in late summer for fall, they finish before summer heat or hard freezes cause trouble. Heat-loving water spinach and amaranth fill the July gap, and heading napa cabbage is a fall crop only. For the full picture, start with Growing Asian Greens in New Jersey.
The short answer for New Jersey
The calendar explains the pick. At the Newark reference station, NOAA’s 1991-2020 climate normals put the last spring freeze (32°F) between March 29 and April 6. The first fall freeze lands between November 4 and November 16. Those dates are the 30 to 70 percent probability band for a 32°F freeze, so inside each window a freeze is close to a coin flip. They come from an airport. 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 elevation. Plan from your county, not from Newark.
Between those two windows the reference station has more than six months without a freeze. That is plenty for quick greens. It is tight for slow ones, and the summer in the middle is hot and humid. Sort your seed packets by speed and heat tolerance, and the choices get easy.
Which Asian greens grow best in New Jersey?
The table sorts them by type. Days are rough counts from sowing and vary by variety.
| Type | Examples | Best season | Rough days from sowing |
|---|---|---|---|
| Fast leaf greens | Mizuna, tatsoi, komatsuna, mustards | Early spring and fall | 25 to 50 |
| Bok choy and choy sum | Baby and full-size bok choy | Fall first, early spring second | 30 to 60 |
| Heading types | Napa cabbage | Fall only | 60 to 80 |
| Heat lovers | Water spinach, amaranth, Malabar spinach | Summer | 35 to 60 for first harvest |
The fast leaf greens are the reliable core. Mizuna and tatsoi can be cut young and regrow, and mustards add peppery flavor to the same bed. Bok choy rewards a fall sowing more than a spring one. Napa wants cool nights while the head fills, which only September and October reliably provide.
The heat lovers are the unexpected winners. Water spinach and amaranth stall in cool spring soil and take off in July and August, when the other Asian greens are bolting. Sow them after frost danger has passed and nights stay warm. For exact sowing windows, see When to Sow Asian Greens in New Jersey.
What will not work here
Three habits cause most of the failures in New Jersey: sowing heading types in spring, sowing fall crops too late, and crowding plants in a humid summer.
Why does bok choy bolt in a New Jersey spring?
Bok choy and napa read lengthening days and warming nights as a signal to flower. New Jersey warms quickly after the April freeze window closes, and by June many days are hot and humid. A bok choy sown in late April may give you a few tender leaves, then send up a flower stalk before the plant reaches full size. Napa sown in spring does worse, because it needs weeks of cool weather to fold into a head. Keep the spring sowings to fast leaf greens and baby-size bok choy, and harvest early.
Spring has a second pest problem. Flea beetles chew pinholes in mizuna, mustards and young bok choy as soon as the leaves emerge. Lightweight row cover laid over the bed at sowing is the usual defense.
What goes wrong with fall sowings?
Fall is the best season, so it is also where timing mistakes cost the most. If the first freeze arrives between November 4 and November 16 at the reference station, and one to two weeks sooner in many suburban and rural yards, a napa sown in mid-September has no time left to head. Fast leaf greens sown that late still give baby leaves, which is why the quick types are the safe bet when the calendar slips.
Does close spacing cause problems in humid summers?
It does. Packed rows hold moisture on the leaves, and that invites fungal leaf spots, rot at the base and slugs. Give bok choy and napa room to reach full size, even if seedlings look lonely at first. Water the soil rather than the leaves, and keep the bed evenly moist from rain and hose combined. Shallow-rooted greens that dry out between soakings turn bitter and bolt sooner.
Winter is a limit too. The mean daily minimum in the coldest month at Newark is 25.5°F, so plenty of nights fall below that. Tatsoi, mizuna and many mustards take light freezes and keep going under cover. Full-size bok choy and napa suffer once nights reach the mid-20s, so do not count on them standing in an open bed through January.
What changes across New Jersey
New Jersey is not one garden. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) runs from zone 6a to zone 7b across the state. That is several steps, so there is no single answer for a gardener in Sussex County and another in Cape May County. The zone is built on one variable, the average annual extreme minimum temperature. It tells you about winter survival. It says nothing about when spring arrives or how hot July gets. To see which zone applies to you, enter your ZIP code on the USDA map. Do not guess from a neighbor’s yard two towns away.
How should northern and high-elevation gardeners adjust?
In the northern counties and the Highlands, spring comes later and fall frost comes earlier than at the Newark reference station. The shift of one to two weeks in each direction is common, and it grows with elevation. Practically, that means starting spring sowings of fast greens later than the reference dates suggest. It also means starting fall sowings earlier, since the freeze that ends the crop comes sooner. Napa is the riskiest choice in the north, because it needs the most days. A gardener there who wants heads should pick an early variety and sow as soon as summer heat eases.
Down the shore and across the southern part of the state, winters are milder, and tatsoi, mizuna and mustards under row cover can often supply greens deep into winter. Summer heat is still serious there, so the bolting and humidity cautions apply everywhere. A gardener near a cold, low pocket or a windy ridge can see frost a full week outside the county pattern, which is why observation matters as much as the map.
Where to check this for your own county
Your state extension service is the next stop. Rutgers New Jersey Agricultural Experiment Station is New Jersey’s land-grant extension, with county offices and Master Gardener volunteers who work with local growing conditions every season.
A county recommendation beats a state one. Any statewide advice averages over very different ground, from the Pine Barrens’ sandy soil to Highlands clay and the warmer shore. The Newark figures above are a reference point, nothing more. What your county office knows is how your own area behaves.
What should you look for from your county office?
- A local planting calendar for fall and spring vegetables, with dates written for your county rather than the whole state
- Varieties that have been grown and trialed in New Jersey conditions, especially for bolt resistance in bok choy and napa
- Guidance on local pests, such as flea beetles in spring and slugs in humid stretches, and on soil testing before you plant
If a county office or Master Gardener hotline can give you a local last-frost and first-frost date, write it down and use it in place of the Newark window. That single swap is worth more than any variety choice.
Checking this against your own garden
Your own observations outrank every date above. Three of them cost nothing and need no equipment.
- Soil warmth by feel. Push your hand into the bed in the morning. If the soil feels distinctly cold, seed will sit and sulk, and spring sowings are early. Warm soil in late summer tells you the ground is still too hot for lettuce-type greens, so fall seeds may need a little shade to sprout.
- First true leaves. The first pair after the seed leaves is a stopwatch. If seedlings reach it quickly, your bed is warm and fast. If it takes two or more, your spot is cooler than the average, and every date should shift later in spring and earlier in fall.
- Frost on the low corner. Note which part of the yard shows white frost first, and which tender plants get nipped. A low, damp corner that frosts early will end your fall crop sooner than a spot near the house wall.
Write down the sowing date, the date of first true leaves and the date of the first flower stalk for one season. A year of three dates gives you a calendar that fits your yard better than any statewide guess, and the bolt date alone tells you how late to sow next spring.
Common questions
Can I grow bok choy in the summer in New Jersey?
Rarely with good results. Heat and long days push it to bolt, and humid weather invites rot. Grow water spinach or amaranth through July and August, and sow bok choy for fall.
What is the easiest Asian green for a first-time grower?
Mizuna and komatsuna are forgiving. They sprout quickly in cool soil, tolerate a light freeze and can be cut young several times. Mustard greens are an easy second choice.
Will Asian greens survive a New Jersey winter outdoors?
Some will. Tatsoi, mizuna and many mustards survive light freezes, and under row cover they often keep going into winter, especially in the milder south and near the shore. Full-size bok choy and napa generally do not.
When should I sow Asian greens in New Jersey?
Early spring for fast leaf greens, and mid to late summer for fall crops, with heading napa sown earlier than the rest. Exact windows shift by county, so check When to Sow Asian Greens in New Jersey and compare it with your county extension calendar.