Sow hardy unusual roots such as salsify, scorzonera and parsnip once the soil can be worked, and hold anything frost-tender until after May 30, the average last spring frost at the St. John’s airport station. Treat that date as the middle of a window, not a safe date. In this province, the roots that need a long, warm season are the ones that struggle.
The short answer for Newfoundland and Labrador
What the two frost dates actually are
Environment and Climate Change Canada’s 1981-2010 normals for the ST JOHN’S A station give an average last spring frost of May 30 and an average first fall frost of October 17. Both are mean dates, which means they sit in the middle of the spread. In one year out of two, the last spring frost falls later than May 30. In one year out of two, the first fall frost arrives earlier than October 17, and the other half of years it comes later. Plant on May 30 and you are flipping a coin on whether a late frost will still hit.
Count the days between those two means and you get about 140. That is the frost-free stretch in an average year, and it shrinks at both ends in a bad one. Every root crop has to fit inside it, or be started indoors and moved out, or be hardy enough to ignore the edges.
One more caveat. These figures come from a single station, and a province is not one climate. Northern and upland districts run weeks behind St. John’s, so the dates below are a starting point for the east coast, not a rule for the whole province.
How the window sorts by type of root
Frost tolerance matters more than the calendar. A root that shrugs off a light frost can go in early. One that blackens at the first cold night has to wait for the far side of May 30, and ideally a week or two past it.
| Type of root | When to sow or plant | Why |
|---|---|---|
| Frost-hardy, direct-sown (parsnip, salsify, scorzonera) | As soon as the soil can be worked, before the May 30 mean | Seedlings tolerate light frost, and slow germination rewards an early start |
| Long-season, frost-tender (celeriac, oca, yacon) | Start indoors, plant out only after May 30 and preferably later, with covers on hand | One frost can end the crop, and the window is only about 140 days on average |
| Perennial tubers (Jerusalem artichoke) | Early spring, once the soil is workable | Hardy once planted, so the calendar matters less than the site |
For a closer look at which roots suit the province’s season, see The Best Unusual Roots to Grow in Newfoundland and Labrador. The broader overview sits at Growing Unusual Root Crops in Newfoundland and Labrador.
What will not work here
The slowest, warmest-season roots are the first casualties. A crop that wants five or six frost-free months does not fit in a window of about 140 days, and the figure is an average. Oca and yacon are the usual examples. Starting them indoors helps, but it does not add warmth to the summer. This page has no local trial results for either, so treat any success as an experiment, not a plan.
Planting frost-tender roots on May 30 and calling it safe is the second mistake. Since the date is a midpoint, half of all years bring a frost after it. A gardener who sets out celeriac seedlings on that exact day loses them to a cold night about as often as not. The cheap fix is patience, plus a row cover on the shelf for the mornings that surprise you.
The fall end of the window is just as loose. October 17 is when frost arrives on average, so in half of years it comes sooner. Anyone counting on mid-October for a tender tuber harvest is gambling on the better half of the distribution. Lift those crops early, or at least watch the forecast from the end of September.
Winter cold is the third constraint, though a gentler one than the coast’s reputation suggests. The mean daily minimum of the coldest month at the reference station is -8.7 °C (16.4 °F). That is an average of the coldest month’s nightly lows, not the record low and not the worst night in a hard year. Hardy perennial roots left in the ground can handle that average. It tells you very little about a deep cold snap in an exposed bed.
Last, a transplanted calendar. A reader in Labrador or in an upland district who takes the St. John’s dates at face value will plant weeks too early. The normals describe one airport, not the province.
This page has no rainfall or humidity figures for the province. It will not rule on watering schedules or on how tightly to space rows, because it cannot back either with numbers. Those questions belong with someone who has local data.
What changes across Newfoundland and Labrador
Natural Resources Canada places St. John’s in zone 6a of the Canadian plant hardiness system, using 1991-2020 normals. That is the zone of one reference city. It is not the zone of the province, and there is no single answer for a territory that stretches from the island’s southern coast to northern Labrador. The page has the 6a figure for St. John’s and no other zone, so it cannot give you the full spread. The map can.
Check where your own community falls on the Canada’s Plant Hardiness Site map rather than assuming it matches the capital. And keep the system straight: Canadian zone 6a is not USDA zone 6a. The Canadian system uses seven climate variables, the USDA one uses a single winter-low measure, and NRCan itself says there are no simple conversions between them. A US gardener comparing notes with a Newfoundland neighbour should compare dates and conditions, not zone numbers.
The two datasets also span different periods. The frost dates are 1981-2010 normals, the hardiness zone is 1991-2020. They are two different pictures of the same place, and the gap between them is a reason to hold the dates loosely.
For readers farther north or at altitude, the shift runs in one direction. Push every sowing date later than the St. John’s means, favour the frost-hardy roots from the table, and treat long-season crops as a gamble. Start indoors anything that can be started, use covers, and plan on a shorter fall harvest. How many weeks to shift depends on your site, which is why the next two sections point you to local sources and to your own garden.
Where to check this for your own county
Newfoundland and Labrador does not use counties the way US states do, so think community or region. The place to start is the provincial Department of Fisheries, Forestry and Agriculture, which is the closest thing to an extension service here. Ask for two things: a local planting calendar for your region, and a list of the varieties that have actually been trialled where you live.
The second item matters more than it sounds. A calendar tells you when frost is likely. A trial tells you whether a given root reached a usable size in conditions like yours. Seed catalogues rarely distinguish the two, and an unusual root with no local trial record is a bet, however good the packet photo looks.
A recommendation for your community beats a provincial one every time. This page is the provincial view, built from one station’s normals and one reference city’s hardiness zone. It sets a reasonable starting point and flags what is likely to fail. It cannot see the frost pocket at the bottom of your lot or the south-facing wall that warms three weeks early.
This page also has no unusual-roots calendar from the provincial department to quote, and it will not borrow one from another jurisdiction. Calendars from other states or provinces are written for other seasons. A lawn calendar from a southern US university, for instance, tells you nothing about salsify in Newfoundland.
Checking this against your own garden
Your own observations outrank every date above. Three are worth watching, and none needs equipment.
- Soil warmth by feel. Push a bare hand a few inches into the bed in the morning. If the soil still feels cold and clammy, tender transplants will sit and sulk. Compare a sheltered bed with an open one: the gap between them is your microclimate, and it may be worth a week or more.
- The first male flowers on local alders or willows. When catkins start shedding pollen near you, spring has moved from tentative to real. Note the date each year. If it lands well after the timing you read for St. John’s, you are on the later side of the province.
- The first true leaves. Sow a few radishes or a row of something quick as a gauge, and note how long they take to show their first true leaves after the seed leaves. Slow means a cold bed and a short season for your slower roots.
Write down the date of your last frost morning and your first one in fall, even if it is just a note on the calendar. After three or four seasons, those scribbles are a better planting calendar than any normal built from someone else’s weather station.
Common questions
Can I sow before May 30?
Yes, for hardy roots such as parsnip, salsify and scorzonera, once the soil can be worked. Frost-tender roots should wait until after the date, and ideally a week or two beyond it, because May 30 is only the average.
Is October 17 my harvest deadline?
Not exactly. It is the average first fall frost at the St. John’s airport station. In half of years frost comes sooner, so lift tender crops early and leave hardy ones for later.
Does zone 6a mean I can grow USDA zone 6 plants?
No. Zone 6a here is a Canadian hardiness zone, built from seven climate variables, and it does not convert to a USDA zone. Choose plants by frost dates and local trial results, not by matching zone numbers.
Do these dates apply in Labrador?
No. They come from one station in St. John’s, and northern and upland districts run weeks behind it. Check your own community’s zone on the NRCan map and ask the provincial agriculture department for a regional calendar.
One last wrinkle: the frost dates come from 1981-2010 normals and the hardiness zone from 1991-2020. If you compare this page with a US source that uses 1991-2020 frost normals, expect small differences that reflect the reference period, not an error on either side.