Between the average last spring frost and the average first fall frost at St. John’s airport sit about 140 days. That is the working season for Asian greens in Newfoundland and Labrador, and it favors quick, cool-tolerant leaf crops over anything that needs months to size up. The numbers behind that, and the places they stop applying, are below.
The short answer for Newfoundland and Labrador
By type, the best Asian greens here are the fast ones: mizuna, tatsoi, komatsuna and mustard greens, plus pak choi grown small or as baby leaf. Treat full-size heading Chinese cabbage and big roots as experiments, not the backbone of the bed.
The reasoning starts with two dates from Environment and Climate Change Canada’s 1981-2010 normals for the St. John’s A station. The last spring frost falls on average on May 30, and the first fall frost on average on October 17. Counting from one to the other gives roughly 140 days. That count is my own arithmetic on two averages, so read it as a rough shape of the season and not a guarantee.
Both dates are means. They describe the middle of a spread, not a safe line. In about one year out of two, a frost still arrives after May 30, and in about one year out of two the first fall frost comes before October 17. Plan around a window with soft edges.
Sorting by type
The page does not carry summer temperature or rainfall figures for the province, so it makes no claim about heat. What it does have is season length and winter cold, and those are enough to sort the types.
| Type | Examples | Fit for this season |
|---|---|---|
| Quick leaf greens, cut-and-come-again | Mizuna, tatsoi, komatsuna, mustard greens | Best bet; harvestable well inside the frost-free window |
| Small pak choi | Baby or mini types | Good, if picked young |
| Heading Chinese cabbage | Full-size napa types | Gamble; needs time to form a head before fall frost |
| Warm-soil crops | Water spinach, amaranth greens | Poor outdoors; indoor or sheltered only |
Many of the leafy types tolerate a light frost, which is why the fall edge of the window matters less for them than the spring edge does. For a sowing schedule built on these dates, see When to Sow Asian Greens in Newfoundland and Labrador. The broader overview sits in Growing Asian Greens in Newfoundland and Labrador.
What will not work here
Start with the long-haul crops. A heading Chinese cabbage sown outdoors on the average last frost date has about 140 days at best before the average first frost, and it has to spend part of that recovering from transplant and part of it forming a dense head. Leaf crops pay you at every stage. A head only pays at the end, and half of all years the end arrives ahead of schedule.
Warm-soil Asian vegetables fare worse. Water spinach and amaranth greens are built for sustained warmth, and a province whose coldest month averages a daily minimum of -8.7 °C (16.4 °F) is not where they come from. Those figures describe winter, but a climate that cold at one end of the year rarely gives warm soil at the other end until well into June. Outdoors, these crops will sulk or stall. Under cover they have a chance.
Then there is the habit of treating May 30 as a planting date. It is the midpoint of the frost risk, so about half of years still see a frost after it. Tender seedlings set out that day, with no row cover and no backup plan, are betting on a coin flip. The greens that survive a late frost are the same ones recommended above, which is another argument for them.
Old normals, new weather
One more caution about the dates themselves. The St. John’s figures cover 1981-2010, not the 1991-2020 period used for the US figures elsewhere on this site, and they come from one airport station. Coastal weather at the airport is not weather in a sheltered inland valley or on a headland. Northern and upland districts run weeks behind these dates, so a gardener there should assume a shorter window than 140 days and lean even harder on the quickest crops.
Spring sowings have their own trap. Long, lengthening days push many Asian greens to bolt, meaning they send up flower stalks and turn bitter. In a short season that makes timing tight on both sides: sow too early into cold and risk frost, sow too late and risk bolting. Small, repeated sowings beat one big one. If a row bolts, little is lost.
What changes across Newfoundland and Labrador
A province is not one garden. The page has one hardiness reading for this territory: zone 6a in Canada’s plant hardiness system, for the reference city of St. John’s, from Natural Resources Canada’s 1991-2020 data. That is the Canadian system, built on seven climate variables, and it does not convert to a USDA zone. Natural Resources Canada itself says there are no simple conversions between the two. Do not read 6a as a USDA number.
It is also a single city’s reading. Newfoundland island and Labrador cover a large spread of climate, from the Avalon Peninsula to the Labrador coast and interior, and this page does not have the full range of zones inside the province. There is no single answer for the whole territory, and anyone who gives you one is guessing. What the St. John’s figures give you is a baseline, not a ruling for your yard.
For the actual zone where you garden, look it up on Natural Resources Canada’s Plant Hardiness Site, which lists zones by municipality. Search for your town, not the nearest big one.
What should a gardener in the north or at altitude shift? Three adjustments follow from the numbers above:
- Push sowing dates later in spring, and expect the final fall harvest to arrive earlier.
- Drop heading types entirely and stay with baby-leaf crops.
- Add protection, such as row cover or a low cold frame, at both ends of the season.
Those are shifts in direction, not exact numbers. How many days earlier or later depends on your own ground, which is what the last section is for.
Where to check this for your own county
Newfoundland and Labrador does not have counties in the way US states do, so read “county” here as your own region or town. The provincial body to start with is the Newfoundland and Labrador Department of Fisheries, Forestry and Agriculture. It is the provincial agriculture department and the closest equivalent to a state extension service.
When you get there, look for two things. First, a planting calendar for vegetables in your part of the province, ideally one that gives sowing and transplant windows by region. Second, any list of varieties that have been trialled locally, because a variety that performs at one research site is worth far more than a seed packet’s general claims. This page has no provincial Asian greens calendar to cite, so if the department publishes one, it outranks anything here.
A regional recommendation beats a provincial one, every time. This page is the provincial view, built on one airport station and one city’s hardiness reading. A local grower, a community garden group or a regional agriculture office knows your frost pockets, your wind and your fog. If their advice and this page disagree, go with theirs.
Checking this against your own garden
Your own observation outranks every date above. Three things are worth watching, and none needs equipment.
Soil warmth by feel. Push your hand into the bed in the morning, a few inches down. If it makes your fingers ache after a minute, it is too cold for anything but the toughest sowing. A bed that warms earlier than your neighbor’s is likely sheltered, and one that stays cold is telling you to wait.
The first true leaves. The first pair of leaves a seedling shows are seed leaves. The second set, the true leaves, show it is establishing. Note how many days that takes from a small test sowing. A slow arrival means cold soil or shade, and it tells you how much margin you really have.
Where frost lands first. After a cold night, walk the yard at dawn. Frost that whitens one corner but spares the wall side shows you a microclimate you can use, with the protected spot for early sowings and the frosty hollow for later, hardier crops. Write down the date of the first frost you see in the fall, because over a few years your own record will tell you more than a 1981-2010 average from the airport.
Common questions
Can I grow bok choy in Newfoundland and Labrador?
Yes, especially small or baby pak choi, which can be harvested well inside the frost-free window. Full-size heads are less dependable.
Is May 30 a safe date to plant out?
No. It is the average last spring frost at St. John’s A, so in about one year out of two a frost still comes after it. Use it as the middle of a window, and cover tender plants.
Does zone 6a mean I should buy seed rated for USDA zone 6?
No. The 6a figure is from the Canadian system, for St. John’s, and it does not convert to a USDA zone. Check the municipality map for your own town instead.
Which Asian green should a first-time grower start with?
Mizuna or komatsuna. Both are quick, forgiving leaf crops that you can cut young and sow again, so one failed row costs little.