In Maryland, spring sowing of Asian greens starts around the last-frost band, April 3 to April 16. Fall sowing runs backward from the first-frost band, October 26 to November 5. Those two windows suit the cool-weather crops (bok choy, tatsoi, mizuna, komatsuna) and leave midsummer mostly off the calendar. The sections below explain how to read these dates and where they bend.
The short answer for Maryland
Start with what the frost dates measure. They come from NOAA’s 1991-2020 Climate Normals, and they are probabilities of a 32°F freeze, not promises. The April 3 to April 16 spring band is where the chance of another freeze sits between 30 and 70 percent. The October 26 to November 5 fall band is the same 30 to 70 percent range for the first freeze of the season. A garden can see a freeze after the later spring date, and it can see one before the earlier fall date. Think of each band as a coin flip getting better or worse, not a gate that opens.
That framing makes the calendar easy to build. Cool-season Asian greens tolerate a light frost, so spring sowing belongs in the weeks around that April band. Waiting for the far end of it costs little. Fall sowing works in reverse. Pick a variety, read its days to maturity on the packet, and count back from the October 26 to November 5 band. A variety rated at 45 days, for example, points to about September 11 if you want it near full size by October 26. Add a cushion, because shortening days slow growth in the last weeks.
| Season | Anchor from the facts | What it means for sowing |
|---|---|---|
| Spring | Last spring frost band: April 3 to April 16 | Direct sow in the weeks around this band. Hardy types go first, tender ones toward the later end. |
| Fall | First fall frost band: October 26 to November 5 | Count backward using days to maturity, plus a cushion for slow late growth. |
| Winter | Coldest-month mean daily minimum: 25.4°F (Baltimore reference) | Expect cold nights below freezing. Plan on covers for anything you want to keep. |
Why the bands are wider than they look
The span between the two bands is more than six months, which is generous for crops that mature in a month and a half or two. Maryland’s problem is not a short season. It is the stretch in the middle, when heat pushes these greens to bolt. Spring sowings get a few cool weeks, fall sowings get a long ramp down, and the two together make a better calendar than any single mid-season planting. For the specific types that fit each window, see The Best Asian Greens for Maryland.
What will not work here
Sowing bok choy in June fails. The seedlings come up fast, then run to flower before the heads fill. That is not a Maryland quirk exactly, but Maryland’s long gap between the spring band and the fall band means a gardener is tempted to treat the whole gap as open season. It is not. The page does not have summer temperature or rainfall figures, so this advice rests on how these crops behave, not on a Maryland heat number. Still, the pattern is consistent: the gap between the bands is for tomatoes and beans, not for the Asian greens.
Late fall sowing is the opposite trap. A seed sown in early November, right on top of the first-frost band, has almost no growing time left. Cold slows germination, and what does sprout stalls as a tiny rosette. You may harvest baby leaves in spring if the plants survive, but that is a bonus, not a plan.
The winter number matters too. The mean daily minimum of the coldest month is 25.4°F at the Baltimore reference station. Average nights below that mark mean many individual nights are colder still, and the hardiness zone range in the next section tells you the cold is harsher in other parts of the state. Tender bok choy will not sit out a Maryland January uncovered. Hardier types like tatsoi and mizuna have a better shot under row cover, but “better shot” is the honest ceiling. Plan the fall crop as a harvest before deep winter, with any survivors as a gift.
Humidity is a separate failure. Maryland summers are humid, and that is the reason close spacing in late summer and early fall sowings backfires. Crowded rows hold moisture on the leaves, and slugs and flea beetles love that setup. Give heads the spacing the packet recommends and thin early, even if the seedlings look better crowded together at first. If you want the broader picture before choosing seed, Growing Asian Greens in Maryland covers the full approach.
What changes across Maryland
Maryland has no single answer. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) lists the state at 5b to 8a. That is six half-zone steps, a wider spread than many people expect from a state you can cross in a few hours. The zone system uses one variable only, the average annual extreme minimum temperature, so it describes how cold the worst winter nights get, not when frost arrives or leaves.
The frost dates in this article are tied to one reference station, so treat them as a central Maryland starting point. Western Maryland, meaning Garrett and Allegany counties, is mountainous and runs weeks later. A gardener there should shift spring sowing later and fall sowing earlier, which shrinks the season at both ends and makes the fall crop the riskier one. The Eastern Shore runs milder, so spring can start sooner and the fall window stays open longer.
Elevation inside a county matters as well. A hilltop and a valley floor a mile apart can differ more than two neighboring counties on a map. Cold air drains downhill on still nights and pools in low spots, so frost hits the bottom of a slope first and leaves it last.
Which zone applies to your address is something to look up on the USDA map by ZIP code, not guess. Once you have it, read it as a rough guide to winter cold. For the sowing dates themselves, the local frost behavior in your yard matters more, and the last section covers how to read that.
Where to check this for your own county
Start with University of Maryland Extension. It is the state’s land-grant extension service, and its horticulture and Master Gardener programs have local staff who know which parts of a county run cold. Two things are worth looking for. The first is a local planting calendar for vegetables, ideally one written for your region of the state rather than Maryland as a whole. The second is any list of varieties trialled in your county, which is better evidence than a catalog description.
A county recommendation beats a state one. This page is the state one. It rests on a single reference station’s frost probabilities and a statewide hardiness range, and that is a long way from your soil. If an extension office tells you its local last-frost date is two weeks off from the band here, follow the extension office.
One limit worth stating: this page does not cite a Maryland extension calendar specifically for Asian greens, so it will not tell you what that calendar says. If you find one, it overrides the general dates above. If you cannot find one, a call or email to your county office is a reasonable next step, and Master Gardeners often answer local timing questions from experience in the same soil you are working.
Checking this against your own garden
Your own observation outranks every date on this page. Three things are worth watching, and none needs equipment.
- Soil warmth by feel. Dig a handful from the bed in the morning. If it is cold and clumps wet in your fist, germination will be slow. A bed that warms sooner than the neighbor’s has a sunnier or better-drained microclimate.
- The first flush of male flowers. Catkins loosening on a nearby hazel or birch, or the first male blooms on any plant in your yard, are a seasonal marker. No study I am citing ties them to Asian greens. Their value is comparison: note the date each year, and you will learn whether your spot runs early or late.
- The first true leaves. The first pair after the seed leaves tells you how fast seedlings develop in your bed. If they arrive well behind the packet’s timing, the spot is cooler or shadier than average, and your fall sowing should go in sooner.
Write down the dates for a couple of seasons. A small notebook beats any regional table, because it records your frost pocket, your south wall, and your slope.
Common questions
Can I sow Asian greens in Maryland in July?
It is a poor bet for most types. The fall band starts October 26, so counting back from it, most sowings belong in late summer, not midsummer. Heat is the main risk, since these crops bolt.
Do I have to wait until after the last frost in spring?
Not for the hardy types. The April 3 to April 16 band is a 30 to 70 percent freeze probability, so a frost remains possible after it. Cool-season greens tolerate a light one, while tender types do better at the later end.
Will Asian greens survive a Maryland winter?
Some may, with cover. The coldest month’s mean daily minimum is 25.4°F at the Baltimore reference, and Western Maryland is colder. Treat survival as a bonus.
Do these dates apply in Garrett or Allegany County?
No, they run later there. Western Maryland is mountainous and runs weeks off the dates here, so shift spring later and fall earlier, and check with your county extension.