Sow Asian greens in Rhode Island twice: from late March through April for a spring crop, and from mid-August into early September for the better fall crop. Sowings in June and July mostly bolt. Both windows are built on the frost dates at the Providence reference station, so a garden inland or on higher ground should start spring sowing later and end fall sowing earlier.
The short answer for Rhode Island
Two probabilities set the calendar. At the Providence airport station, NOAA’s 1991-2020 U.S. Climate Normals put the last spring freeze at 32°F between April 7 and April 17, and the first fall freeze between October 24 and November 3. Both ranges are the 30 to 70 percent probability band for a 32°F freeze, so a freeze after the spring dates, or before the fall dates, still turns up in some years. They describe the airport. Suburban and rural gardens typically see the last spring frost later and the first fall frost earlier, often by one to two weeks.
When can you sow Asian greens outdoors in spring in Rhode Island?
Bok choy, tatsoi, mizuna and komatsuna take light frost, so they do not have to wait for the last-frost band. Sow as soon as the soil is workable and no longer soggy. That means the last spring frost can come later in your own garden than at the reference station. What ends the spring season is the lengthening days and warming weather of late May and June, which push the plants to flower. Sow baby-leaf types in small batches through the season, and put full-size bok choy in once the soil can be worked. For direct-sown crops, the days on the seed packet count from sowing.
When should you sow Asian greens for fall in Rhode Island?
Count back from the October 24 to November 3 band. Full-size bok choy sown as the days shorten has time to size up, and shortening days also hold bolting back. Napa cabbage is worth starting early in the group.
| Type | Spring sowing | Fall sowing |
|---|---|---|
| Baby-leaf mizuna, tatsoi, komatsuna | Late March through April | Mid-August to mid-September |
| Full-size bok choy | Early to mid April | Mid-August to early September |
| Napa cabbage | Skip in spring | First half of August |
These are Providence-area dates. Inland, start spring sowing a week or two later and end fall sowing a week or two earlier.
What will not work here
Why do summer sowings fail in Rhode Island?
Summers in southern New England are warm and humid, a poor fit for crops that want cool nights. Bok choy and mizuna sown in June or July run to flower before the leaves reach a useful size, and flea beetles pepper whatever foliage does come up with tiny holes. Napa cabbage fares worst in spring. It forms a tight head slowly, and a spring sowing usually meets the heat of June before the head fills.
August brings a different problem. Seeds sown into warm soil for the fall crop sit in a bed that dries quickly. A once-a-week watering habit fails here, and the seed bed needs light watering until the seedlings are up.
What goes wrong with late sowings and crowded rows?
Sowings after mid-September grow into shortening, cooling days. Their seedlings are still small when the first freeze band arrives in late October. Winter will not rescue them either. The mean daily minimum of the coldest month at Providence is 22.1°F, which is too cold for these greens to carry on in the open. Past early autumn, a cold frame or row cover is the only way to keep a harvest going.
Humidity punishes tight spacing. Late-summer fog and heavy dews keep crowded leaves wet for hours, which invites leaf spot and slugs. Give full-size bok choy room between plants, and thin baby-leaf rows so air moves through them.
What changes across Rhode Island
The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) places the state in zones 6a to 7b. That spans four half-zone steps in a small state, so no single zone answers for everybody. The zone system rests on one variable, the average annual extreme minimum temperature. It tells you what survives the worst night of winter. It says less about when to sow a crop that lives for a few months.
For sowing dates, the same logic applies in a simpler form. The coast and islands run milder, so check your own county for frost dates. Gardens in the northwest hills, and any low spot where cold air pools, run colder. Someone in those places should move spring sowing a week or two later and bring the fall deadline a week or two earlier. A shaded north-facing bed behaves like a garden farther north than it really is, even a few miles from the shore.
To find your own zone, use the USDA map and look up your ZIP code. The right zone for a given yard depends on the exact location, so check the map yourself. For which types suit each end of the season, see The Best Asian Greens for Rhode Island, and for the wider picture of the crop, Growing Asian Greens in Rhode Island.
Where to check this for your own county
The first stop is University of Rhode Island Cooperative Extension, the state’s land-grant extension service. Look for two things there: a local planting calendar for cool-season vegetables, and any list of varieties that have been grown in trials near you. A variety that held up in a Kent County trial is a better bet for your bed than one that only looks good in a catalog.
Ask the same questions of whoever answers your call or email. When do you typically get the last spring frost where I live? Which brassicas have bolted early in recent summers? Extension staff see the season play out across many gardens, and that experience matters more than any single weather station.
A county recommendation beats a state one. The dates in this article are a state-level reference built on one airport station, the right starting point but a rough one. When an extension calendar for your county disagrees with the dates above, follow the county.
Checking this against your own garden
Your own observations outrank every date here. Three are worth watching.
- Soil warmth by feel. Squeeze a handful from a few inches down. If it crumbles instead of smearing, the bed is workable. Hold your hand in the soil for a minute. Cool is fine for Asian greens, while a numbing cold means wait. A south-facing raised bed will pass this test days before a shaded corner.
- The first true leaves. The rounded seed leaves come first, followed by the true leaves with the crop’s real shape. If true leaves take weeks to show, the bed is colder than the calendar assumed. If they show fast in April, that spot is a warm microclimate, and you can sow it earlier next year.
- Frost on your own lawn. Note the morning the grass turns white in fall and compare it with the forecast. An earlier frost in your yard than in town marks a frost pocket, and the fall deadline there comes sooner.
Write the dates down for two or three seasons. A notebook entry of when the soil crumbled, when seedlings came up and when bolting began will give you a calendar tuned to your yard.
Common questions
Can you sow Asian greens in winter in Rhode Island?
Only under cover. The mean daily minimum of the coldest month at Providence is 22.1°F, so open beds stop growing. A cold frame or low tunnel can carry hardy types like tatsoi and mizuna through the cold months, though growth is slow.
Is October too late to sow Asian greens?
In an open bed, yes. The first fall freeze at the reference station falls between October 24 and November 3, and rural gardens often get it sooner. Under a cold frame, a quick baby-leaf sowing can still give a small harvest.
How early before the last frost can I sow?
Several weeks, as long as the soil is workable. Seedlings handle light frost. A hard freeze can still flatten tender seedlings, so keep a sheet or row cover handy for nights forecast to fall below freezing.
Does my hardiness zone tell me when to sow?
No. The zone reflects the coldest winter extreme, while sowing dates follow spring and fall frost. Use your zone for perennials and your local frost dates for these greens.