For Delaware, The Best Asian Greens are the cool-season ones: bok choy, tatsoi, mizuna, komatsuna and mustard greens, sown for fall first and spring second. Heat-lovers such as amaranth and water spinach earn a place only in summer’s gap. At the reference city, frost dates of April 3 to April 14 in spring and October 26 to November 7 in fall leave room for two good seasons. Summer is the weak link.
The short answer for Delaware
Choose by type rather than by cultivar name. Hardy, fast leaf greens are the backbone, napa cabbage is a fall specialist, and the tropical greens fill July and August. The two shoulder seasons suit the first group, and the summer between them suits the last.
Reading the frost dates correctly
The reference figures come from the NOAA NCEI 1991-2020 Climate Normals for an airport weather station (station USW00013781). The last spring frost falls between April 3 and April 14, and the first fall frost between October 26 and November 7. These dates are a probability of a 32°F freeze, in the 30 to 70 percent band. They are not a promise. In any given year the freeze can arrive before or after the window.
They are also an airport’s numbers. 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. Treat the dates as a starting point for the reference city and adjust from there.
Matching type to season
| Type | Examples | Best season in Delaware | Main limit |
|---|---|---|---|
| Compact heads and rosettes | Bok choy, tatsoi | Fall first, spring second | Bolts if spring warms quickly |
| Cut-and-come-again leaves | Mizuna, komatsuna, mustard greens | Spring, fall, and under cover into winter | Turns coarse and bitter in summer heat |
| Heading cabbage | Napa cabbage | Fall | Needs a long cool stretch to form a head |
| Heat-lovers | Amaranth, water spinach | After the last frost through summer | Frost-tender, finished by the first fall frost |
If you grow only one type, make it the cut-and-come-again group. Mizuna and mustards forgive late sowing, uneven watering and a few cold nights better than anything else on the list. For month-by-month sowing dates, see When to Sow Asian Greens in Delaware. The wider how-to lives in Growing Asian Greens in Delaware.
What will not work here
Slow and heading types sown in spring
The gap between the last frost (April 3 to April 14 at the reference city) and the onset of Delaware’s hot, humid summer is short. Napa cabbage sown in spring is the classic casualty. It needs weeks of cool weather to wrap a head, and it often runs to seed instead. Bok choy sown late in spring does the same thing in miniature. This page carries no summer temperature figure, so it cannot give you a bolting threshold. The pattern is reliable anyway: whatever has not sized up by the time summer turns hot is likely to bolt.
Close spacing in humid air
Delaware summers and early falls are muggy, and bok choy packed tightly holds that moisture at its base. Rot and slugs follow. Space plants so their leaves barely touch at full size, and water the soil rather than the foliage. Gardeners in the sandy soils common in the southern part of the state face the opposite problem. Water drains fast there, and shallow-rooted greens stall quickly if irrigation slips for even a few days, so a thin mulch earns its keep.
Tropical greens left to overwinter, and fall sowings made too late
Water spinach and amaranth will not survive winter here. The mean daily minimum of the coldest month is 25.6°F, which means many nights run colder than that. Anything frost-tender should be treated as a one-season crop and pulled at the first fall frost.
Hardy greens are not immune either. Tatsoi and mizuna take light frost well, but with a mean low of 25.6°F, exposed plants will take damage in January and February. A row cover or a simple cold frame changes that. Without protection, plan on a fall harvest rather than a winter one.
Sowing too late in fall is the other mistake. The first fall frost falls between October 26 and November 7 at the reference city, and a rural garden may see it one to two weeks sooner. Daylight shortens fast by then. Seedlings that were still small in October often sit and wait rather than grow, so a late sowing yields baby leaves at best.
What changes across Delaware
Delaware is small, but it is not one garden. The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places the state in zones 7a to 8a. That spans three half-zone steps (7a, 7b and 8a), so there is no single answer for the whole state. The USDA system rests on one variable, the average annual extreme minimum temperature, so it describes how cold the worst nights get. It does not describe how long the growing season lasts.
That distinction matters for greens, which are mostly annuals. For them, frost dates matter more than the zone number. The zone still tells you something: a colder zone means harder winter nights and a shorter margin for fall crops. Generally, the northern end of the state sits toward the colder end of that range and the southern and coastal areas toward the milder end, though local terrain and distance from the water shift the picture.
In practice, a gardener toward the colder end should do three things:
- Start fall sowings earlier, since the first frost may arrive ahead of the reference dates.
- Put row cover on sooner and expect tatsoi and mizuna to need it earlier.
- Hold off on spring sowing of tender types a little longer.
A gardener toward the milder end can stretch the fall harvest and may get winter cuttings under cover. They should also expect heat and humidity to push spring crops to bolt sooner, so spring sowings should go in early.
To find your own zone, use the USDA Plant Hardiness Zone Map and enter your ZIP code. Do not guess from a neighbor’s garden or a seed packet. Then check your frost dates against the next section.
Where to check this for your own county
Your state extension service is the next stop. In Delaware, that is University of Delaware Cooperative Extension. Look for two things there. The first is a local planting calendar for vegetables in your county, with spring and fall sowing windows. The second is any list of varieties trialled in your county, meaning what was actually grown and judged for bolting, disease and cold tolerance rather than what a catalog claims.
This page does not have either one. It has the reference-city frost dates, the coldest-month minimum and the state’s hardiness range. It has no county-level calendar, no county trial results and no summer temperature figures. If a county page and this page disagree, believe the county page.
A county recommendation beats a state one because Delaware has just three counties (New Castle, Kent and Sussex) with very different soils, coastal influence and frost timing. This page is the state-level view. It tells you which types to try and which to skip, but the sowing dates it implies come from an airport, and a rural lot may differ by a week or two.
When you call or email your county office, bring three specifics: your town, whether the garden is in a low spot or on a slope, and which of the types above you plan to grow. The more specific the question, the more useful the answer.
Checking this against your own garden
Your own observations outrank every date on this page. Three are worth tracking, and none needs an instrument.
Soil warmth by feel. In early spring, push your hand into the bed in the morning. If it feels cold and damp, seeds will sit and may rot. If the soil crumbles and feels neutral or slightly cool, you can sow. A bed against a south-facing wall will warm days ahead of a shaded corner, and that gap is your microclimate showing itself.
The first true leaves. Sow a small test row of mizuna or komatsuna, then watch for the first true leaves, the ones that look like the adult plant and not the rounded seed leaves. How fast they appear tells you how well that spot suits cool-season crops. If a spring test row bolts early while a shadier row holds, you have found where your garden runs hot.
The first frost in your lowest spot. Cold air pools in low ground. Note where frost first shows on grass or car windshields in October, and when. If it lands one to two weeks before the reference window of October 26 to November 7, your fall plan should shift earlier by the same margin.
Common questions
Can I grow Asian greens through a Delaware winter?
Only the hardy ones, and only with protection. Tatsoi, mizuna and mustards can carry on under a row cover or cold frame. With a coldest-month mean minimum of 25.6°F, unprotected plants will be damaged. Tropical types such as water spinach end at the first fall frost.
Is spring or fall the better season?
Fall is the stronger season for most types. Cool weather arrives gradually and holds, while spring often turns hot quickly and pushes plants to bolt. Spring still works for fast cut-and-come-again greens sown early.
Should I sow on the last frost date?
No. April 3 to April 14 is the reference-city window where the chance of a 32°F freeze runs 30 to 70 percent. Hardy greens can go in before it. Tender types should wait until after it, and a rural garden should add a week or two.
What can I grow in July and August?
Amaranth and water spinach, both heat-lovers. Most other Asian greens struggle in Delaware’s summer. Many gardeners use that stretch to prepare beds for fall sowing, since cool-season seedlings need time to size up before the first fall frost, which falls between October 26 and November 7 at the reference city.