Sow Asian greens in Prince Edward Island twice: in spring as soon as the soil can be worked, and again from late July through early September for a fall crop. Skip the middle of summer for bok choy, tatsoi, mizuna and their relatives, which bolt when days are long and warm. Frost dates frame both windows, but they are averages, and the margins matter. This calendar belongs to the wider guide on Growing Asian Greens in Prince Edward Island.
The short answer for Prince Edward Island
Sow Asian greens from late April to late May, pause through June and July, then sow again from late July to early September. Spring crops finish before the summer heat, and fall crops mature in cooling weather ahead of the October frosts.
The frost dates come from the Charlottetown A station, using Environment and Climate Change Canada’s 1981-2010 climate normals. On average the last spring frost falls on May 16 and the first fall frost on October 17. The reference station has about 154 frost-free days between those two dates.
Both dates are means, the midpoint of a window. In one spring out of two, the last frost falls later than May 16. In one fall out of two, the first frost arrives earlier than October 17. Neither is a safe date, and the station sits in one spot on an island with many different districts.
Asian greens suit that uncertainty better than most vegetables. Seedlings of bok choy, mizuna, tatsoi and komatsuna shrug off a light frost, so there is no reason to wait for May 16. Seed goes in when the soil crumbles in your hand instead of smearing, which usually means late April or early May. A sheet of row cover over the bed adds a few degrees and keeps flea beetles off the young leaves.
Fall sowing works by counting back from October 17. Baby leaves take roughly three to five weeks from sowing. Full heads of bok choy need six to eight weeks, and napa cabbage takes longer still to form a firm heart. That puts the sowing dates at:
- Late April to mid-May: first spring sowing, ideally under row cover.
- Mid-May to late May: main spring sowing, with baby-leaf types going in until the end of the month.
- Late July for napa cabbage, early to mid August for full-size bok choy, and up to early September for baby leaves.
Day length does the rest. Plants sown in spring are racing the longest days of the year, and plants sown in August are running downhill into shorter ones. Which varieties suit each window is covered in The Best Asian Greens for Prince Edward Island.
What will not work here
A June sowing of full-size bok choy or napa cabbage is the classic failure. The plants reach maturity around the longest days of the year, and warm, long days push them to send up a flower stalk before the head fills. The leaves turn bitter and the harvest is gone in a week.
Late fall sowing fails for the opposite reason. With a mean first frost of October 17, and an early frost in half of all years, a head of napa cabbage sown in late August has nowhere near enough time. Even where the frost holds off, light levels drop through October and growth slows to a crawl. Baby leaves of mizuna or tatsoi are the only reasonable crop to sow that late, and they should be in by early September.
Winter is the other wall. The mean daily minimum of the coldest month at the reference station is -12.1 °C (10.3 °F). That is an average, so some nights run well below it. Almost no Asian green survives a Prince Edward Island January in an open bed. A low tunnel or cold frame can stretch the harvest into November and sometimes beyond, but plan on the crop ending there and sow again next spring.
Early sowing has its own trap. Seed pushed into cold, saturated soil in early April tends to rot rather than sprout. Seedlings that do emerge and then sit through a long cold snap can bolt early, because a stretch of cold tells some brassicas that a season has already passed. If the ground is still wet and cold in late April, wait a week.
Damp maritime weather also punishes tight spacing. Bok choy sown thickly and left unthinned holds moisture between the leaves, and in cool, humid spells that invites slugs and fungal leaf spots. Give full-size heads about 15 to 20 cm (6 to 8 in) between plants, and thin baby-leaf rows early. Flea beetles, which leave small shotgun holes in spring seedlings, are best stopped with row cover laid on the day of sowing, since they arrive before most gardeners notice them.
What changes across Prince Edward Island
The reference city sits in Canadian hardiness zone 5b, according to Natural Resources Canada’s 1991-2020 normals. That is a Canadian zone and it does not convert to a USDA zone. The Canadian system draws on seven climate variables, the USDA system on one, and Natural Resources Canada says plainly that there are no simple conversions between them. Its own example is zone 4a, which overlaps nine USDA zones, from 3a to 7a. So a USDA-zone chart from a seed catalog will not tell you what 5b means here.
The zone also describes one city. A province is not a single climate, and the frost dates above come from the same station. Northern and upland districts run weeks behind Charlottetown in spring, and their fall frost can arrive earlier. There is no single answer for the whole island, only a spread around the reference figures.
A workable rule: if your garden is in a cooler district, push the spring sowing back a week or two and move the fall sowing forward by about the same. Sites close to open water tend to warm slowly in spring and hold their warmth longer into autumn, so shoreline beds often behave differently from fields a few kilometres inland. Low spots where cold air pools can frost a week before the hill above them.
To see where your own municipality falls, use Natural Resources Canada’s plant hardiness map and look up your community. Keep in mind that the frost dates cover 1981-2010 and the zone covers 1991-2020, so they describe different periods and should not be blended into one number. For annual greens that finish in two months, frost timing matters more than winter survival anyway.
Where to check this for your own county
The Government of Prince Edward Island’s agriculture pages are the right starting point. Staff there deal with growing conditions in the island’s counties and districts, and they can point you to local growers’ advice and seasonal updates.
Look for two things. The first is a planting calendar for your district, with sowing dates for cool-season brassicas that you can compare with the Charlottetown averages. The second is a list of varieties that have been grown locally. A variety that performs well in a trial plot a few kilometres from your garden tells you more than a seed packet written for the whole continent.
Ask directly about the dates of the last spring frost and first fall frost in your area, and whether the district runs cooler than Charlottetown. If you want to compare the varieties themselves, our guide to the best Asian greens for Prince Edward Island covers the types worth trying.
A recommendation for your own county or district beats one written for the whole province. A provincial calendar has to cover the warm south shore and the cooler districts at once, so it lands on dates that work acceptably almost everywhere and perfectly nowhere. Use the provincial dates as a starting point, then adjust to what local advice and your own beds tell you.
Checking this against your own garden
Your own observations outrank every date above. Three are worth watching, and none needs equipment beyond your hands.
Soil warmth by feel. Push your bare hand a few centimetres into the bed in late April. If the soil crumbles and does not feel icy or sticky, the first sowing can go in. If it clumps wet or makes your fingers ache, wait. Beds that reach that point a week before a neighbor’s are your warm microclimate, and they get the earliest sowing.
The first true leaves. Seedlings first show two rounded seed leaves, then the first true leaves, which look like small versions of the mature plant. Note how many days that takes after sowing. If a spring sowing needs far longer than expected to reach that stage, the bed is cold, and the next sowing should wait or go under cover.
The first frost in your low spots. In fall, walk the garden at dawn after a clear, calm night and see where frost has settled. The beds that whiten first mark where your first frost will come early, and those should get the earliest fall sowing and a cover ready. Sow the sheltered beds last.
Write the dates down for a season. After one year you will have a calendar tuned to your own ground, which is more useful than a number from a station that may be miles away.
Common questions
Can I sow Asian greens before the last frost in Prince Edward Island?
Yes. Seedlings of bok choy, mizuna and tatsoi tolerate a light frost, so sowing can start in late April or early May once the soil crumbles. Row cover protects them during hard nights. The mean last frost of May 16 is only the midpoint of a window.
Is it too late to sow Asian greens in September?
For full heads, yes. For baby leaves of mizuna, tatsoi or komatsuna, early September still works, because they are ready in three to five weeks. After that, growth slows and the October frost is a real risk.
Can I sow Asian greens in June or July?
Most will bolt in the long, warm days. If you want to sow then, choose fast baby-leaf crops, give them afternoon shade, and keep them watered. Late July is the time to start napa cabbage for the fall.
Will Asian greens survive winter outdoors?
Not in an open bed. The coldest month averages a daily low of -12.1 °C, and many nights are colder. A low tunnel or cold frame can extend the harvest into November or later, but plan to sow again in spring.