Sow Asian greens in Quebec twice a year: from mid-April to late May, and again from mid-July through early September. Midsummer sowings meet heat and long days, and most of these crops respond by flowering before they make a harvest. Both windows hang on frost dates, and those shift a great deal across the province, so the dates below are a starting point.
The short answer for Quebec
Sow hardy Asian greens such as mizuna, tatsoi, komatsuna and baby bok choy outdoors from mid-April to late May. For fall, sow napa cabbage in mid to late July and everything else between late July and early September, depending on how long the crop takes to mature. Those windows are built around two averages from the Montreal/St-Hubert airport station: the last spring frost falls on average on May 6, and the first fall frost on average on October 5.
Both dates are means. In one year out of two, the last spring frost comes after May 6, and in one year out of two the first fall frost arrives before October 5. Treat each date as the middle of a window that can slide a couple of weeks either way, never as a safe date.
Spring sowing can start before May 6 because Asian greens are cool-season brassicas. Seedlings shrug off a light frost, and a sheet of row cover adds a few degrees on a sharp night. What they dislike is the opposite end of the season, when warm days and long daylight tell the plant to run to seed.
| Type | Days from sowing | Spring sowing | Fall sowing |
|---|---|---|---|
| Baby leaves (mizuna, tatsoi, baby bok choy) | 25 to 40 | Mid-April to late May | Mid-August to early September, with cover late in the window |
| Full-size bok choy, komatsuna | 40 to 60 | Mid-April to mid-May | Late July to early August |
| Napa cabbage heads | 60 to 80 | Risky, best under cover | Mid to late July |
The fall dates fall earlier than a plain count back from October 5 would suggest, because growth slows as days shorten and nights cool. Giving each crop a week or two of margin matters more in October than in May. For choosing among the types themselves, see The Best Asian Greens for Quebec, and for the wider picture, Growing Asian Greens in Quebec.
What will not work here
Napa cabbage sown in late August will not form a firm head. With roughly five weeks left before the average first frost, and growth slowing the whole time, you get a loose rosette at best. Heading types need to be in the ground by late July.
June sowings of bok choy and napa fail for the opposite reason. Daylight is at its longest and the soil is warm, so the plants send up a flower stalk before the heads or thick stems fill out. A June row of mizuna or tatsoi will still give a few baby cuttings, but the leaves turn sharp and the plants bolt fast. Flea beetles also peak in late spring and early summer, and they leave seedlings full of tiny holes unless row cover goes on at sowing.
Sowing too early can backfire too. A bed of bok choy or napa started in early April and then hit by weeks of cold nights may flower in response, long before summer arrives. The May 6 average means roughly half of all springs still bring a frost after that date. Hardy greens tolerate it, but a stretch of cold after an early sowing is a different matter. Under a low tunnel, the early start works much better.
Overwintering in open ground is out. The mean daily minimum of the coldest month is -14.1 °C. Mizuna and tatsoi take light frost and a few degrees below freezing, but none of the Asian greens lives through weeks of nights near that figure. Late fall crops can be stretched into November under a tunnel, and that is the realistic limit.
Close spacing also works against you in fall. Damp, cool nights favor slugs, and tightly packed bok choy keeps the base of the plants wet. Give full-size plants room to spread and thin baby rows early.
What changes across Quebec
Montreal sits in Canadian hardiness zone 5b, according to Natural Resources Canada’s plant hardiness map. That is the zone of the reference city, and Quebec stretches far beyond it. The province covers several zones, so no single sowing date fits everyone. The same crop that is ready in early October near Montreal may be under snow weeks sooner in the Saguenay, Abitibi or Gaspé.
The Canadian system is built on seven climate variables, and it does not convert to a USDA zone. Canadian zone 4a, for example, overlaps nine different USDA zones. Don’t carry a Quebec zone number over to an American seed catalog’s advice. To find your own zone, look up your municipality on Canada’s Plant Hardiness Site.
For a short-season annual like bok choy, zone matters less than the frost dates in your own backyard. Northern and upland districts run weeks behind the Montreal station, in spring and in fall. Higher gardens warm slowly and cool early. Shift both windows inward: start spring sowing later, once the soil can be worked, and finish fall sowing weeks earlier.
In a colder district, favor the quick crops. Baby leaves of mizuna, tatsoi and komatsuna fit a short season far better than a napa head. A low tunnel or row cover buys back some of the lost time on both ends. In the milder pockets near the St. Lawrence lowlands, the windows above hold, with the usual year-to-year swings.
Where to check this for your own county
A recommendation from your own county or regional municipality (MRC) beats a provincial one. Dates built on one airport station give a provincial average, and your garden may sit weeks away from it in either direction. The local advice is what to follow once you find it.
Start with the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec (MAPAQ). Look there for two things: a planting calendar that covers your area, and any variety trials run in your region for Asian greens or closely related brassicas such as cabbage and mustard. Much of the material will be in French, so searching for “calendrier de semis” along with your region’s name is a quick way in.
A good local calendar gives you an average last frost for your own area. That one number will move your spring window more than any other. Trial results tell you which varieties resisted bolting and flea beetle damage in soils like yours.
If you can’t find a calendar for your area, ask a nearby garden center, a market gardener or a local gardening club. Growers who sell Asian greens at the farmers’ market know exactly when the first bolting starts in your district.
Checking this against your own garden
Your own observations outrank every date above. Three are worth watching.
- Soil by feel. In spring, squeeze a handful of soil from just below the surface. If it crumbles and feels cool rather than cold and soggy, seeds will germinate. A bed that reaches that point two weeks before the shaded corner shows how much warmer your best spot runs.
- First true leaves. Sow a short test row a week or two before the main planting. How long it takes to show real leaves, beyond the first rounded pair, tells you how fast your soil is warming.
- First frost damage. When frost first whitens the lawn or blackens basil and squash leaves, note the date and the spot. A low corner that frosts first is a frost pocket. Your fall sowing deadline should be counted back from that date, not from October 5.
Write these dates down for two or three seasons. After that, your notes will beat any calendar, including this one.
Common questions
Can I sow Asian greens in June in Quebec?
You can, but most will bolt. Long days and warm soil push bok choy and napa to flower before they size up. Quick baby leaves like mizuna sown in partial shade and watered often will give a short harvest.
How late can I sow bok choy for fall?
For full-size plants, aim for late July to early August, since the mean first fall frost is October 5. Baby bok choy can go in until early September, with row cover as nights cool.
Do Asian greens survive winter in Quebec?
Not in open ground. The coldest month averages a daily minimum of -14.1 °C. Hardy types survive light frost and can be harvested into November under a tunnel, but they will not overwinter.
Should I start Asian greens indoors?
It is rarely needed, as most grow quickly from seed sown outdoors. Starting napa cabbage indoors in early spring risks bolting if the seedlings get chilled. For fall napa, direct sowing in mid to late July works well.