Sow Asian greens in Vermont twice a year: in spring, from the first workable soil until about the last frost, and again from late July through August for fall. The hot stretch between mostly produces bolted plants. The frost dates behind this advice come from Burlington, the mildest corner of the state, so gardeners in the mountains and the north should lean later in spring and earlier in fall. The basics of the crop are covered in Growing Asian Greens in Vermont.
The short answer for Vermont
Early spring and late summer are the two sowing windows, and the second one is usually the better of the two. At the Burlington reference station, NOAA’s 1991-2020 Climate Normals put the last spring 32°F freeze between April 30 and May 10. The first fall freeze falls between October 3 and October 13. Those dates mark the 30 to 70 percent probability band of a 32°F freeze, so a freeze after May 10 or before October 3 still happens in some years. Treat them as the middle of a spread.
When should you sow Asian greens in spring?
Start as soon as the soil is workable, which in Vermont can be April, and keep sowing in small batches until late May. Bok choy, mizuna, tatsoi and komatsuna seedlings take a light frost, so there is no need to wait for May 10. Lay row cover over the bed for the nights that dip below freezing. Seeds sown in cold, saturated ground sit and rot, so wait for soil that crumbles in your hand.
When should you sow Asian greens for fall?
Sow from late July through August, counting back from the October 3 to October 13 freeze window. Baby-leaf types are often ready soon after sowing. Full-size bok choy and napa cabbage need longer, so they go in at the early end of the window. Check the seed packet, since days to maturity count from sowing for direct-sown greens. The fall crop matures as days shorten and nights cool, which is what these plants like. For help choosing types, see The Best Asian Greens for Vermont.
| Type | Spring sowing | Fall sowing |
|---|---|---|
| Baby leaf (mizuna, tatsoi, baby bok choy) | April to late May, in repeated small sowings | August, with a last sowing into early September under cover |
| Full-size bok choy | April to early May, before long days arrive | Late July to mid-August |
| Napa cabbage and daikon | Poor fit, since they bolt in spring | Late July to early August |
What will not work here
Sowing in June and early July fails more often than any other timing. Around the summer solstice Vermont gets long days of daylight, and Asian greens read long days and heat as a signal to flower. Plants sown then send up flower stalks before they make a usable head or a full rosette of leaves.
Spring sowings of napa cabbage and daikon fail for the same reason. Both need a long stretch of cool weather to form a head or a root, and a spring that goes from mud to warm days quickly gives them neither. Sow them in summer for fall harvest instead.
A late fall sowing fails too. The first freeze arrives between October 3 and October 13 at the reference station, and the mountains see it sooner. Seedlings that come up in late September face short days and cold nights, and they grow very slowly. A bed sown in October may sit as seedlings until winter. The cutoff for baby greens is early September, and only with cover.
Winter is the hardest limit. The mean daily minimum of the coldest month at Burlington is 12.9°F. Most Asian greens handle a light frost, but weeks of nights near that figure kill uncovered plants. The USDA hardiness zone does not help here, because it describes the coldest extreme that perennials must survive. A low tunnel or cold frame can extend the harvest into November and sometimes beyond, but it does not make these crops winter-hardy.
Spring brings its own problems. Flea beetles peppering young leaves with tiny holes can ruin an unprotected spring sowing. Row cover set at sowing and kept on until the plants are established prevents most of that damage. Fall sowings, as insect pressure drops, usually need less protection.
What changes across Vermont
The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places Vermont in zones 3b to 5b. That is a wide spread, and there is no single answer for the state. The dates above describe the lake-moderated Burlington area, and the Green Mountains and the Northeast Kingdom run substantially shorter seasons.
In the north and at elevation, sow spring crops later, because the soil stays frozen or soggy longer. Shift the fall window earlier too. A garden high in the hills may need its fall bok choy in the ground in late July. Its first freeze can arrive well before the Burlington band of October 3 to October 13, so a low tunnel is worth setting up there before you need it.
The Champlain Valley and the lower river valleys are the warmest parts of the state, and the Burlington dates fit them best. Valley floors and hollows are another matter. Cold air drains into them on clear nights, so frost can land there days before it reaches a nearby slope. Elevation and local topography change the dates, which is why a gardener some distance from Burlington may sow off the schedule.
Zone numbers are zone numbers. To find yours, use the USDA Plant Hardiness Zone Map and enter your ZIP code. Use it as a rough guide to how far your garden sits from Burlington, but do not treat it as a sowing date.
Where to check this for your own county
Go to University of Vermont Extension, the state’s land-grant extension service. Ask for the office covering your county, and look for two things: a local planting calendar with spring and fall dates, and a list of Asian green varieties that have been grown in your area.
The first tells you the frost dates and sowing windows for your part of the state. A statewide calendar averages very different places, so a county calendar is more accurate. A grower near Brattleboro and one near the Canadian border are working with different seasons, even though both are in Vermont.
The second item, varieties tried locally, matters as much. Bolting and cold tolerance vary a lot between varieties of the same crop, and a bolt-resistant bok choy or a cold-tolerant tatsoi may do well where another cultivar fails. When extension staff or a local garden group have grown a type in your area, take their word over a seed catalog’s.
Extension also runs a plant diagnostic service and Master Gardener volunteers who answer questions about local pests and soil. If flea beetles or maggots wreck your first sowing, ask them what has worked in your county.
Checking this against your own garden
Your own garden outranks every date above, and three observations will tell you how to adjust.
- Soil by feel. Squeeze a handful from a few inches down. If it holds a sticky, cold ball, wait. If it crumbles and feels cool rather than icy, sow. Watch which bed reaches that point first each year, since that is your warmest spot.
- First true leaves. After the seed leaves, the first true leaves of a test sowing show how fast your soil is warming. If they appear quickly, you are ahead of schedule. If they take longer, your site is colder than the average and later sowings will be safer.
- Where frost lingers. On cold mornings, notice where white frost sits longest on the lawn or on tender plants such as basil. Frost that arrives early in a low corner tells you that part of the garden needs row cover first in fall and sowing later in spring.
Write the dates in a notebook for a few seasons. Your own garden’s pattern will soon be more reliable than any published average.
Common questions
Can I sow Asian greens in July in Vermont?
Yes, from late July, for a fall crop. Sow napa cabbage and daikon then, and full-size bok choy in late July or early August. Plants sown in June or early July tend to bolt in the long days.
Can Asian greens go out before the last frost?
Most can. Bok choy, mizuna, tatsoi and komatsuna seedlings tolerate light frost, and the last spring freeze at Burlington falls between April 30 and May 10. Row cover protects against hard freezes and flea beetles.
Do Asian greens survive a Vermont winter?
Not uncovered. The mean daily minimum of the coldest month at Burlington is 12.9°F, which kills most of them. A cold frame or low tunnel carries some types, such as tatsoi and mizuna, well into late fall.
Is Burlington’s frost calendar right for my garden?
Only if you garden near Lake Champlain. The Green Mountains and the Northeast Kingdom have substantially shorter seasons, so shift spring sowing later and fall sowing earlier. University of Vermont Extension can give you a calendar for your county.