On Prince Edward Island, the best Asian greens are the quick, cool-tolerant ones: mizuna, tatsoi, komatsuna and bok choy. They do as well in a late-summer sowing for fall as in spring. Napa cabbage works if the timing is right. Heat lovers like water spinach rarely earn the bed space on the Island.
The short answer for Prince Edward Island
Choose by type. Fast leaf greens (mizuna, tatsoi, komatsuna, baby bok choy) are the safest bet, compact bok choy comes second, and napa cabbage and the taller Chinese broccoli types need a well-timed fall sowing. Anything that wants warm nights and a long, hot summer is a poor match for a cool maritime island.
At the Charlottetown A station, the mean last spring frost falls on May 16 and the mean first fall frost on October 17, which leaves about 154 frost-free days between them. Both dates are midpoints. In one year out of two, the last frost comes later than May 16, and in one year out of two, the first fall frost arrives later than October 17. They come from Environment and Climate Change Canada normals for 1981-2010, so recent years can run a little differently. A province is also not one climate, and northern or upland districts run weeks behind the Charlottetown station.
Which types fit the Island’s season best?
Days to harvest on a seed packet count from sowing. The ranges below are typical packet figures, and the shorter number usually means baby leaves.
| Type | Typical days from sowing | Fit for the Island |
|---|---|---|
| Mizuna | 21 to 40 | Excellent, takes light frost, works in spring and fall |
| Tatsoi | 25 to 45 | Excellent, low rosette handles cool, damp weather |
| Komatsuna | 25 to 40 | Very good, forgiving of both cool and mild warm spells |
| Bok choy (baby and full size) | 30 to 60 | Good, best as a fall crop |
| Choy sum and gai lan | 40 to 60 | Fair, needs a timely fall sowing |
| Napa cabbage | 60 to 80 | Fair, only from a late-summer sowing |
The fall crop is where the Island shines. Count back from October 17 and allow extra time because growth slows as days shorten, then check with your provincial extension office for the sowing window in your district. Fall sowings never face the long June days that push these plants to flower early.
When should you sow them?
The calendar needs more room than this summary allows. When to Sow Asian Greens in Prince Edward Island walks through spring and fall windows crop by crop, and Growing Asian Greens in Prince Edward Island covers the wider picture of soil, spacing and care.
What will not work here
Start with the plants built for hot weather. Water spinach, Malabar spinach and amaranth greens all want warm nights and warm soil for months. An average of 154 frost-free days sounds generous, but the soil takes a while to warm in spring, and a cool Island summer never delivers the sustained heat these crops expect. You would be giving up bed space for a few thin harvests.
Which spring sowings fail in a short, cool season?
Napa cabbage is the usual casualty. Sown in mid-May, a 70 to 80 day variety heads up in late July, right when days are longest, and plants that have already weathered a run of cold nights as seedlings tend to bolt instead of forming a head. The same logic catches bok choy sown too early under cold nights. Seedlings that get chilled for a stretch often shoot up a flower stalk before the plant has reached a useful size.
Sowing on May 16 itself is a coin flip as well. That date is the average, so half of all years still have a frost after it. Mizuna and tatsoi shrug off a light frost, but seedlings of the more tender types do not, and a sheet of row cover is cheap insurance.
Can Asian greens stay in the ground over winter?
Not in an open bed. The coldest month has a mean daily minimum of -12.1 °C (10.3 °F), and that is the average night, so the cold snaps run lower. Asian greens are cool-season crops, not the winter-proof kind like kale, and a hard freeze ends them. A low tunnel or cold frame buys a few extra weeks of harvest in November and December, but it does not carry the crop through to spring.
Does damp weather cause trouble?
Yes, and more than most gardeners expect. The Island’s air is humid, and fall brings fog and rain. Plants set shoulder to shoulder hold moisture in the leaves and give slugs a place to hide. Give full-size bok choy and napa room to spread, and thin baby greens early rather than late. Soggy spring soil also rots seed, so wait until a handful of earth crumbles instead of smearing. In spring, flea beetles pepper mizuna and other mustard-family leaves with tiny holes, and floating row cover laid at sowing is the simplest fix.
What changes across Prince Edward Island
The reference city for the Island sits in zone 5b of the Canadian plant hardiness system, using Natural Resources Canada’s 1991-2020 normals. That is a Canadian zone and does not convert to a USDA zone. The Canadian system blends seven climate variables, while the USDA system uses one, and Natural Resources Canada itself says there is no simple conversion between them.
The zone describes one city, not the whole Island. Northern and upland districts run weeks behind the Charlottetown station, so there is no single answer for the province. To see where a particular address falls, use Natural Resources Canada’s Plant Hardiness Site, which lets you look up a municipality instead of guessing from a neighbor’s garden.
How should gardeners in colder parts of the Island adjust?
Shift everything toward the cool end. Hold spring sowings a week or two later than the Charlottetown dates, and start the fall crop earlier. If your first fall frost tends to arrive earlier than October 17, count back from your own frost date instead and sow full-size bok choy and napa in the last days of July. Favor the fastest types, such as mizuna, tatsoi and baby bok choy, because they have the shortest distance to cover before cold ends the season.
Local features matter too. Low spots collect cold air on still nights, so a bed in a hollow can frost while a slope a few yards up stays clear. Beds near the water often get frost later in fall, since the surrounding water holds heat, but the wind off the coast shreds big leaves and slows seedlings. A windbreak of fencing or a row of taller crops on the exposed side often pays for itself in one season.
Where to check this for your own county
The provincial agriculture department is the first stop, and Prince Edward Island’s agriculture department is the place to start. Once there, look for three things:
- a planting calendar for your part of the Island, with frost dates drawn from the nearest weather station;
- vegetable varieties that have been trialled locally, and which brassica types did well;
- advice on pests and diseases that hit mustard-family crops in your area, such as flea beetles and slugs.
The Island has three counties (Prince, Queens and Kings), and conditions differ between them and between the coast and the interior. A recommendation for your county beats one for the whole province, because a province-wide answer is an average. The Charlottetown dates and the zone 5b figure are good starting points for planning, but they describe one station and one city.
If your county has trial results or an advisor, ask which Asian greens are being grown nearby and when growers sow them. Local market growers and experienced neighbors often know which varieties bolt, which ones shrug off a wet October, and how late a fall crop can go in.
Checking this against your own garden
Your own beds outrank every date above. Three observations will tell you more about your microclimate than any table.
First, feel the soil. In spring, press a handful together: if it forms a sticky ball that stays smeared, it is too wet, and if it crumbles and feels cool but not icy, hardy greens can go in. Do the same test on a sheltered bed and an open one. If the sheltered bed crumbles a week sooner, you have a head start there every spring.
Second, watch the first true leaves. After the two seed leaves, the first true leaf appears, and how many days that takes after sowing tells you how warm the bed really is. Seedlings in a cold hollow lag behind those on a south-facing slope. Note the difference once and you can adjust sowing dates for each bed in later years.
Third, watch for the first sign of bolting and the first frost damage. A bok choy center that starts stretching upward is heading for flower, and the date tells you how long that bed’s spring window lasts. In fall, the first blackened leaves on basil or squash show when frost reaches your lowest spot. Keep a notebook with these dates for a few years and you will have a local calendar more reliable than any average.
Common questions
Can you grow bok choy on Prince Edward Island?
Yes. Bok choy grows well on the Island, especially from a late-summer sowing that matures in cool fall weather. Spring sowings can work too, but they risk bolting if seedlings are chilled by cold nights or if the plants mature in the long days of June and July.
Is it too late to sow Asian greens in September?
Not for the fast types. Mizuna, tatsoi and komatsuna can be harvested as baby leaves a few weeks after sowing, so a late sowing can produce a crop before the mean first frost of October 17. Later sowings need row cover or a cold frame, and full-size bok choy and napa are too slow to start that late.
Will Asian greens survive an Island winter?
Not in an open bed. The mean daily minimum of the coldest month is -12.1 °C (10.3 °F), and that is colder than most Asian greens tolerate. A cold frame or low tunnel can extend harvest into late fall and early winter, but plan on replanting in spring.
Is Canadian hardiness zone 5b the same as USDA zone 5b?
No. The two systems are built on different climate measures, and Natural Resources Canada states that there are no simple conversions. For example, Canadian zone 4a overlaps nine USDA zones, from 3a to 7a. For Asian greens, frost dates and your own bed observations matter more than either zone number.