At 47.62 degrees north, the reference city for this territory gets 15 hours and 47 minutes of daylight on the longest day of the year. That single number decides almost everything about which onion varieties will actually form a bulb here, and which ones will just sit in the ground making leaves. Short-day types are ruled out completely. Long-day varieties are the ones built for this much summer light.
How long your longest day is
Onions don’t respond to soil temperature or rainfall the way tomatoes or beans do. They respond to the clock, or to how many hours of light hit the leaves each day. Once a plant’s genetic threshold is reached, it stops putting energy into new leaves and starts pushing everything into a bulb. Get that threshold wrong for your location, and you get a plant that never receives the signal to switch over. It just keeps growing green tops until the season runs out.
St. John’s, the reference station for this data, sits at 47.62 degrees north and reaches 15 hours 47 minutes of daylight at the June solstice. That’s well into long-day territory. Long-day onion varieties are bred to wait for 14 to 16 hours of daylight before bulbing, and a location that hits nearly 16 hours on its longest day gives them exactly the trigger they need, with room to spare. Intermediate-day varieties, which bulb around 12 to 14 hours, would technically get their signal earlier in the season here too, but they’re not the group this territory is built around. Short-day onions are a different story entirely: they start bulbing at roughly 12 hours of daylight, a threshold this region blows past for most of the growing season, which means they’d bulb too early, while the plant is still small, and give you tiny, disappointing onions.
| Day-length group | Bulbing trigger | Result at 47.62N |
|---|---|---|
| Short-day | ~12 hours | Bulbs far too early, stays small |
| Intermediate-day | ~12-14 hours | Not the target group for this latitude |
| Long-day | 14-16 hours | Matched to local daylight, the group to plant |
One thing worth flagging before anyone assumes this settles the question province-wide: Newfoundland and Labrador is not one climate zone. St. John’s sits on the southeastern edge of Newfoundland island, but Labrador stretches far north of it, into latitudes well above 50 and even 60 degrees. A gardener in Labrador City or further up the coast gets noticeably more summer daylight than someone in St. John’s, which pushes them even more firmly into long-day territory and, at the very far north, potentially into varieties bred for extreme daylight. If you garden outside the immediate St. John’s area, it’s worth checking your own latitude rather than assuming this figure applies exactly to you.
Which varieties bulb in Newfoundland and Labrador
Fourteen of the twenty-eight onion varieties documented on this site have a published latitude range that covers 47.62 degrees north, meaning their breeding matches the daylight pattern this territory actually gets. These are the ones worth planting:
- Ailsa Craig (long-day, 38-60N)
- Barolo (long-day, 38-55N)
- Blush (long-day, 38-55N)
- Bridger (long-day, 35-50N)
- Frontier (long-day, 40-50N)
- New York Early (long-day, 38-50N)
- Patterson (long-day, 38-55N)
- Red Long of Florence (intermediate-day, 38-50N)
- Red Long of Tropea (intermediate-day, 35-48N)
- Redwing (long-day, 43-65N)
- Rossa di Milano (long-day, 38-50N)
- Safrane (long-day, 42-50N)
- Talon (long-day, 42-50N)
- Walla Walla Sweet (long-day, 35-55N)
One more sits right at the edge: Powell, a long-day variety rated for 43 to 47 degrees north. That range ends just below St. John’s latitude, but published bounds aren’t a hard cutoff, they’re a continuum, so Powell may still bulb reasonably well here. Treat it as a variety to trial in a small bed rather than one to bet the whole season on.
Now the part that actually matters more, because it explains a failure a lot of gardeners have already had without knowing why. Thirteen varieties documented on this site have published ranges that sit below 47.62 degrees north, which means they are not built for this much summer daylight and will not bulb reliably here:
- Cabernet (intermediate-day, 35-45N)
- Calibra (intermediate-day, 35-45N)
- Candy (intermediate-day, 33-40N)
- Elsye (intermediate-day, 32-45N)
- Expression (intermediate-day, 32-45N)
- Gabriella (short-day, 20-35N)
- Madalyn (short-day, 20-35N)
- Monastrell (intermediate-day, 35-46N)
- Red Carpet (long-day, 40-45N)
- Red Rock (short-day, 30-36N)
- Scout (intermediate-day, 32-46N)
- Sierra Blanca (intermediate-day, 32-45N)
- White Castle (short-day, 30-38N)
If any of those names look familiar, there’s a reason. A lot of the onion sets and bulbs sold in general garden centers, especially the short-day and intermediate-day types bred for southern and mid-latitude markets, end up on shelves everywhere regardless of local daylight. Plant one of these this far north and the pattern is almost always the same: strong, healthy-looking leaves all summer, a plant that never bulges at the base, and then rot setting in once the tops finally flop and the bulb that never formed sits wet in the soil through a cool, damp fall. It isn’t a watering problem or a fertilizer problem. It’s a variety that was never going to bulb at this latitude, no matter how well it was cared for.
When to plant onions in Newfoundland and Labrador
Planting timing for onions follows the day-length group, and that’s exactly why it looks different from one part of the country to another. In mild-winter regions, growers plant long-day and intermediate-day onions in the fall, overwinter the small plants, and let them resume growth and bulb the following summer. That approach depends on winters that don’t hard-freeze the ground for months at a stretch. Newfoundland and Labrador doesn’t offer that option. This is spring-planting territory, full stop, because a long-day onion started here needs its full growing season ahead of it, not behind a winter that would kill it outright.
The frame for that spring window comes from the frost data at the ST JOHN’S A station: an average last spring frost on May 30, and an average first fall frost on October 17. That gives a growing season of roughly four and a half months between the two average dates. Onions started from sets or transplants can go in the ground around, or shortly before, that average last frost date, since young onion plants tolerate a light frost far better than most vegetable seedlings. Many gardeners in this climate start onions indoors from seed in late winter, several weeks before the last frost, then move the young plants outside once the ground has thawed and can be worked, giving the bulbing process as much daylight as possible before the long-day threshold arrives at the solstice.
What matters most here is not treating either frost date as a guarantee. These are averages published by Environment and Climate Change Canada from the 1981-2010 Canadian Climate Normals, drawn from a single station in St. John’s. An average means the midpoint of a spread, not a safe line: in roughly half of all years, frost arrives later than May 30 in spring, or earlier than October 17 in fall. Treat both dates as the center of a window worth watching closely, not as a date to circle on the calendar and plant blindly by. And as with the latitude figure itself, anyone gardening away from the immediate St. John’s area, particularly inland, at higher elevation, or further into Labrador, should expect their own frost window to run later in spring and earlier in fall than what this station records.