Asian greens do well in Wyoming when they are timed for the cool ends of the season. Sow in spring once the soil has lost its chill, then sow again in late summer so the crop matures into cool fall weather. The mean last spring frost falls between May 7 and May 18, and the mean first fall frost between September 24 and October 5. Row cover covers the gaps. The broader guide to Growing Asian Greens: Fast, Cold-Hardy, and Prone to Bolting covers the crop family itself.
When the soil is warm enough in Wyoming
The calendar comes first. At NOAA station USW00024018, the 1991-2020 Climate Normals put the last spring frost between May 7 and May 18. That range is the 30 to 70 percent band of 32°F freeze probability, so a freeze can still arrive after the later date in a cold year. Plan around the range and keep a sheet of row cover within reach.
A frost date describes the night air. Asian greens respond to the soil, and the soil warms after the freezing nights end. Snowmelt leaves beds cold and soggy, and a north-facing or shaded bed holds that chill longest. Seed sown into cold, wet ground sits and may rot before it sprouts. A better signal than the date is the bed itself. Push a soil thermometer in at seed depth for several mornings running and watch for a steady climb rather than one warm afternoon. A handful of soil that crumbles instead of squeezing into a wet ball is ready to be worked.
When can you sow Asian greens in Wyoming in spring?
As soon as the bed is workable and the soil has begun to warm, quick leafy types such as bok choy, tatsoi and mizuna can go in, ideally under a low cover. Treat that spring crop as a short race. Days lengthen fast toward June, and long days push these plants to bolt, which means sending up a flower stalk and turning the leaves bitter. Harvest young, as baby leaves or small heads, and the crop is finished before the stalk appears.
Flea beetles are the usual spring visitor. They chew small shot holes in seedling leaves, and a cover laid at sowing keeps them off. Asian greens are brassicas, and so are turnips and rutabagas. All of them share their pests and diseases with cabbage, kale and mustard. A bed that grew any of those last year has not been rotated for this crop, so check the crop rotation guide on this site before choosing where to sow.
Variety choice matters here too, but names that work in one valley may fail in another. The state extension service, linked in the last section, is the place to ask what has been trialled near you.
How long the season lasts here
Roughly 130 frost-free days at 6,000 feet separate the mean last spring frost (May 7 to May 18) from the mean first fall frost (September 24 to October 5). Frost is possible in any month at higher elevations, so a garden in a mountain valley may get far less than that. Season extension is not optional in much of the state. Row cover, low tunnels and a cold frame turn a marginal window into a usable one.
What a window of that length allows is a second sowing. Fast leafy types sown in spring can be cut and cleared before midsummer, and a second sowing in the cooling weeks of late summer gives a fall crop that sweetens as nights chill. The gap between them falls in the hottest weeks, when the bed is better used for something else or left shaded and mulched. The succession sowing guide on this site shows how to space repeat sowings so the harvest arrives in waves instead of all at once.
Is it worth transplanting Asian greens in a short season?
Where the window is short, as it is at higher elevations, the first sowing may be the only one. Then every week counts, and starting seedlings indoors or under cover can buy that week. The catch is the roots. Asian greens dislike being disturbed, and a seedling that has circled its cell or been left too long in the tray can stall or bolt after it goes out. Slide a seedling out of its cell before planting and look at the root ball. White roots holding the soil together are ready. A thick tangle wound around the base means the plant waited too long in the tray.
Direct sowing avoids the problem altogether, and in the lower and warmer parts of the state it is usually the simpler choice. Gardeners on the plains side of the border can compare notes with Growing Asian Greens in Nebraska, where the season runs longer and the sowing windows shift accordingly.
Heat and water in Wyoming
High elevation and dry air shape summer here. Hot afternoons still happen, and they are more frequent in the lower basins and on the eastern plains than in the mountain valleys. Nights stay cool nearly everywhere. Heat is therefore a smaller problem for this crop than it is in the humid South, and summer water comes mostly from the hose, since much of the state is dry. Asian greens belong to the second half of the year, so the facts that govern them are the first frost and the winter low.
The first frost sets how late a sowing can still finish. The mean first fall frost falls between September 24 and October 5. Take the days to maturity printed on the seed packet, which count from sowing for direct-sown greens, and subtract them from the earlier date, September 24. Then add a margin, because growth slows as days shorten and nights cool. Sowings made after that point will make baby leaves at best.
Can Asian greens stand through a Wyoming winter?
The winter low decides that. The mean daily minimum of the coldest month is 18.1°F at Cheyenne (NOAA 1991-2020 Climate Normals). The USDA Plant Hardiness Zone Map (2023) puts the state anywhere from zone 3a to 6a, so a yard in Cheyenne and a high mountain valley can differ by several zones. The USDA zone is built on the average annual extreme minimum, which is colder than the monthly mean.
For most Asian greens in an open bed, the first hard freeze is the end. The hardiest types, such as tatsoi and mizuna, handle light frosts well and hold longer under a low tunnel or cold frame, where they can stand into the cold months. Even those need the cover to be vented on sunny days and closed before hard nights.
Dry air and wind can scorch leaves in summer and again under a cover in autumn. A layer of mulch keeps the root zone cool and even. Water in the morning so foliage dries quickly. Where summers turn cool and damp instead, expect powdery or downy mildew, slow ripening and rot at the base of crowded plants, which is why spacing and airflow matter.
Roots such as daikon and turnips come out of the ground before the soil freezes hard. Before putting any root away, inspect it, and then inspect it again. A soft patch, a weeping spot or a moldy crown ends the question, and a firm exterior does not make it safe. Throw those out and keep only roots that are clean and dry.
Which Asian greens suit Wyoming
Choose by type, and let the season length and the weather do the choosing. The table sets out what each condition favors.
| Condition | What it favors | Types to look at |
|---|---|---|
| Short season, high elevation | The earliest, fastest types, harvested young | Baby bok choy, tatsoi, mizuna, komatsuna |
| Hot spells in July | Airflow, shade and mulch at the root, plus bolt-resistant types | Loose-leaf greens, sown for fall |
| Cool, damp stretches | Disease resistance listed on the seed packet | Any type, with wide spacing |
| Cold autumn nights | Types that tolerate frost and sweeten in the cold | Tatsoi, mizuna, mustard greens |
Heading types such as napa cabbage and long roots such as daikon take longer and need an on-time start, so they suit the lower, warmer parts of the state or a gardener ready to use covers. Faster leaf types are the safer first choice. Where summers turn damp, put disease resistance first. Packets describe it, and the extension office can say which problems show up in your area.
Wyoming runs from the edge of the Great Plains to high mountain valleys, and a variety that thrives in one can fail in the next. The only recommendation worth following is one trialled near you, so ask University of Wyoming Extension which varieties have done well in your county. Gardeners in humid summer regions can compare this with Growing Asian Greens in Connecticut, where mildew rather than dry air sets the rules.
Common questions
When can I plant bok choy outside in Wyoming?
The mean last spring frost falls between May 7 and May 18, but the soil matters more than the date. Sow once the bed is workable and warming, ideally under a row cover, and harvest young before long days trigger bolting. A second sowing in late summer often does better.
Do I need row cover or a cold frame?
In most of the state, yes. Frost is possible in any month at higher elevations, and the season is short even at lower ones. A cover protects spring seedlings, keeps flea beetles off, and extends the fall harvest past the first frosts.
Can I plant turnips or rutabagas where cabbage grew?
No. Turnips and rutabagas are brassicas, like Asian greens, cabbage, kale and mustard, and they share the same pests and diseases. Planting one after another in the same bed leaves those problems in place. Follow the crop rotation guide on this site and move the whole family to a new bed each year.
Which varieties should I buy?
Choose a type that fits your season, then ask University of Wyoming Extension which varieties have been trialled where you garden. Elevation changes a great deal across the state, and local trial results are more reliable than any list of names.