New Brunswick’s growing season calls for long-day onion varieties, full stop. At 46.11 degrees north, the province logs 15 hours and 34 minutes of daylight on the longest day of the year, well past the 14-to-16-hour trigger that long-day onions need before they’ll start forming a bulb. Fifteen documented varieties fall squarely inside that window here, while eight short-day types will never size up properly this far north. A handful of others sit in a blurred middle ground worth understanding before you order seed.
The short answer for New Brunswick
The figure that matters isn’t temperature, it’s daylight. Onions read the length of the day to decide when to stop making leaves and start making a bulb, and that threshold is fixed by genetics, not by how warm the soil feels. Environment and Climate Change Canada’s climate-station data puts Moncton at 46.11 degrees north, and at that latitude the longest day of the year runs 15 hours and 34 minutes from sunrise to sunset. Clemson Cooperative Extension’s Home & Garden Information Center notes that short-day onions begin bulbing around the 12-hour mark, while long-day types hold off until day length reaches somewhere between 14 and 16 hours. New Brunswick’s summer daylight sits right in that long-day sweet spot.
Long-day varieties that match this latitude
Fifteen of the varieties documented on this site have published ranges that cover 46.11 degrees north, which means their bulbing trigger lines up with what a New Brunswick summer actually delivers:
- 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)
- Powell (long-day, 43-47N)
- 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)
Powell is worth flagging on its own: its published range of 43 to 47 degrees north is narrow, and Moncton sits almost dead center in it. That’s about as close to a purpose-built match as this list gets for New Brunswick gardens.
What will not work here
Eight varieties documented on this site carry published ranges that stop well south of New Brunswick, and the mechanism behind their failure isn’t the one gardeners usually expect. It isn’t that these onions refuse to bulb at all. It’s that they bulb too early. A short-day onion is genetically wired to start forming a bulb once daylight hits roughly 12 hours, and in New Brunswick the calendar reaches that mark in early spring, long before the plant has had time to grow the leaf mass a full-size onion needs. The bulb forms on schedule, but on a plant that’s still mostly seedling. The result is a small, often flattened onion, not a total crop loss, and definitely not a feeding problem, whatever the fertilizer bag might suggest.
- Candy (intermediate-day, 33-40N): New Brunswick’s summer daylight runs well past the top of this range, so it behaves like a short-day type here, bulbing early and small.
- Gabriella (short-day, 20-35N, no page of its own on this site): triggers at 12 hours of daylight, a point reached here while the plant is still juvenile.
- Madalyn (short-day, 20-35N, no page of its own on this site): same early-trigger problem, compounded by a range built for much lower latitudes.
- Red Rock (short-day, 30-36N, no page of its own on this site): bulbs on a plant with too few leaves to fill it out.
- Red Sensation (short-day, 25-35N): a Gulf Coast and desert Southwest onion, badly mismatched to a Maritime summer.
- Texas Grano 1015Y (short-day, 25-35N): among the shortest-day types on this list, it bulbs earliest of all here.
- Vidora (short-day, 25-35N): same short-day trigger, same undersized result.
- White Castle (short-day, 30-38N, no page of its own on this site): closer to the New Brunswick range than the others on this list, but still south of where the day-length math works.
Plant any of these in a New Brunswick garden and you won’t get a failed crop in the dramatic sense. You’ll get a harvest of onions the size of golf balls, sitting where you expected softball-sized storage onions. That’s a seed-catalog mismatch, and it’s fixed at ordering time, not at harvest time.
What changes across New Brunswick
Moncton, the reference city behind these figures, sits at 46.11 degrees north, but New Brunswick itself stretches close to three degrees of latitude, from around 45 degrees near the Bay of Fundy and the Maine border to nearly 48 degrees along the Chaleur Bay coast up by the Acadian Peninsula. That spread matters more than it looks like on a map, because every fraction of a degree shifts the length of the longest day.
| Region | Approximate latitude | Longest-day daylight | What it changes |
|---|---|---|---|
| Southern NB (Fundy shore, St. Stephen area) | ~45N | Slightly under 15h34 | Closer to the lower bound of intermediate-day ranges; the eight blurred-zone varieties below are more likely to bulb reliably |
| Moncton (reference city) | 46.11N | 15h34 | Baseline for every figure on this page |
| Northern NB (Acadian Peninsula, Chaleur Bay) | ~48N | Slightly over 15h34 | Further from blurred-zone bounds; shorter frost-free window pushes toward an earlier indoor start |
That southern edge is where eight more varieties come into play, ones whose published ranges land within about a degree and a half of 46.11 degrees north: Cabernet (intermediate-day, 35-45N), Calibra (intermediate-day, 35-45N), Elsye (intermediate-day, 32-45N), Expression (intermediate-day, 32-45N), Monastrell (intermediate-day, 35-46N), Red Carpet (long-day, 40-45N), Scout (intermediate-day, 32-46N), and Sierra Blanca (intermediate-day, 32-45N). None of these have a firm cutoff. A published range is a documented continuum, not a fence, so a gardener near St. Stephen sits closer to where these varieties are known to perform, while a gardener up near Bathurst is pushing them toward the edge of what’s been recorded. Either way, they’re a maybe here, not a confirmed match and not an exclusion.
Checking this against your own garden
Every figure on this page is anchored to Moncton. That’s a solid reference point for most of the province, but not a substitute for knowing your own coordinates, especially if you’re gardening near either tip of New Brunswick rather than in the middle of it.
- Look up your own latitude if you’re gardening more than an hour’s drive from Moncton in either direction, north toward Bathurst or south toward St. Stephen. A quick search of your town’s coordinates will do it.
- Check your local frost dates rather than assuming Moncton’s apply. Coastal and inland pockets within the same province can differ by a couple of weeks in either direction.
- Contact your provincial agriculture extension service, or the nearest Cooperative Extension office if you garden close enough to the border to shop seed catalogs out of Maine, and ask what long-day varieties local growers have had success with.
- Recheck the eight blurred-zone varieties against your specific latitude before ordering, since a degree or two in either direction changes whether they’re a safe bet.
- Note your microclimate. A south-facing slope or a spot sheltered from Fundy fog can run measurably warmer than the regional average, though it won’t change the daylight math itself.