New York City sits at 40.78 degrees north, and on the longest day of the year the sun stays up for 14 hours and 56 minutes. That single number decides which onions will actually bulb in your garden. It rules out the whole category of short-day onions sold in big-box garden centers every spring, and it opens the door to long-day and intermediate-day varieties instead. Nineteen of the varieties tracked on this site fit the state’s latitude range, but several popular ones will not.
How long your longest day is
Two numbers matter here, and they come from the same weather station: 40.78 degrees north latitude, and 14 hours 56 minutes of daylight on the summer solstice, both measured at the New York City reference site (station USW00094728, NOAA NCEI). Everything else in this article is a consequence of those two figures.
Onions do not bulb because the weather warms up. They bulb because of day length, full stop. A short-day onion starts converting its energy into a bulb once daylight reaches roughly 12 hours, a threshold published by Clemson Cooperative Extension’s Home & Garden Information Center. At New York’s latitude, days pass that 12-hour mark by mid-March and keep climbing toward nearly 15 hours by late June. A short-day onion planted here starts bulbing while it is still a small seedling, because the trigger arrives so early in the season. The plant has no time to build the leaf mass a real bulb needs, so it stops small.
Long-day and intermediate-day varieties need something closer to 14 to 16 hours before they switch modes. New York’s 14 hours 56 minutes on the solstice lands squarely inside that window, which is exactly why the state’s onion-growing tradition runs through long-day and intermediate-day types, not the short-day onions that dominate Southern seed racks. Knowing this, the next step is figuring out When to Plant Onions in New York so your chosen variety has time to bulb properly.
One caution worth repeating: 40.78 degrees is the latitude of New York City specifically, not the whole state. New York stretches from Long Island up past the Adirondacks, a span of several degrees of latitude. A gardener near Plattsburgh or Massena is farther north than the reference point used here, and their longest day runs a little longer than 14 hours 56 minutes. If you garden near the state’s northern edge, it’s worth checking your own latitude before locking in a variety, the difference of a degree or two can nudge a borderline variety from “should bulb” to “won’t quite make it,” or the reverse.
Which varieties bulb in New York
Nineteen varieties documented on this site have published latitude ranges that cover 40.78 degrees north. That’s the largest working list of any latitude band, which makes sense given where New York sits: right in the overlap zone between long-day and intermediate-day territory. For the full breakdown, see The Best Onion Varieties for New York.
Varieties that work here
- Ailsa Craig (long-day, 38-60N)
- Barolo (long-day, 38-55N)
- Blush (long-day, 38-55N)
- Bridger (long-day, 35-50N)
- Cabernet (intermediate-day, 35-45N)
- Calibra (intermediate-day, 35-45N)
- Elsye (intermediate-day, 32-45N)
- Expression (intermediate-day, 32-45N)
- Frontier (long-day, 40-50N)
- Monastrell (intermediate-day, 35-46N)
- New York Early (long-day, 38-50N)
- Patterson (long-day, 38-55N)
- Red Carpet (long-day, 40-45N)
- Red Long of Florence (intermediate-day, 38-50N)
- Red Long of Tropea (intermediate-day, 35-48N)
- Rossa di Milano (long-day, 38-50N)
- Scout (intermediate-day, 32-46N)
- Sierra Blanca (intermediate-day, 32-45N)
- Walla Walla Sweet (long-day, 35-55N)
Three more sit close enough to a published boundary to call them edge cases rather than a flat yes: Candy (intermediate-day, 33-40N), Safrane (long-day, 42-50N), and Talon (long-day, 42-50N). All three are within about a degree and a half of New York City’s latitude. Latitude ranges aren’t hard cutoffs, they’re a continuum, so these may bulb here, better in a warmer microclimate or a slightly earlier planting than a guaranteed success.
Varieties to skip
This is the part a lot of gardeners find out the hard way, usually after buying a bag of onion sets at a hardware store without checking the label’s day-length type. Two failure patterns show up here, and they look different in the garden.
- Gabriella (short-day, 20-35N), plant grows leaves, bulbs too early and too small
- Madalyn (short-day, 20-35N), same pattern, tiny onions instead of no onions
- Red Rock (short-day, 30-36N), bulbs prematurely at this latitude
- White Castle (short-day, 30-38N), same story, undersized bulbs
- Powell (long-day, 43-47N), day never gets long enough here to trigger bulbing
- Redwing (long-day, 43-65N), same problem, needs latitudes farther north than New York City provides
The first four are short-day varieties planted too far north: New York’s daylight passes their 12-hour trigger so early in spring that the plant is still small when bulbing starts, giving you a small onion instead of no onion. The last two are the opposite mistake, long-day varieties bred for latitudes farther north than New York City, where summer days stretch past 16 hours. Here, the day never reaches the length those varieties are waiting for. The plant just keeps making leaves all season, then rots in the ground once the growing season ends. No bulb at all, not even a small one, a different failure than the short-day mistake, and the more frustrating one, since it can take an entire summer to find out.
When to plant onions in New York
New York City’s frost dates, drawn from the 1991-2020 NOAA climate normals at station USW00094728, put the last spring freeze between March 23 and April 3, and the first fall freeze between November 14 and November 27. Those are 30-70% freeze-probability windows, meaning there’s meaningful frost risk on either side of them, treat them as a planning frame, not a guarantee.
Because New York sits in long-day and intermediate-day territory, the planting calendar here looks nothing like a mild-winter Southern garden, where short-day onions go into the ground in fall and overwinter as small plants. That approach doesn’t work when your varieties need 14-plus hours of daylight to bulb: those hours only show up as summer approaches, so the plant needs its head start earlier in the same calendar year, not the year before.
In practice, that means starting onion seed indoors in late winter, roughly eight to ten weeks before the last spring frost, then transplanting hardened-off seedlings outside as soon as the soil can be worked, often a few weeks before that final frost date since onions tolerate cold better than heat. Sets and transplants purchased locally follow the same window, timed to get several weeks of leaf growth in before daylight climbs into the bulbing zone in June.
Central Park’s frost dates describe New York City and its immediate surroundings, not the Adirondacks, the Southern Tier, or the Tug Hill Plateau, where both frosts arrive earlier in fall and linger later in spring. A gardener in those regions is working with a shorter frost-free season than the dates above suggest, and should push spring planting a little later and expect to finish harvest a little earlier. Source for these frost windows: NOAA NCEI U.S. Climate Normals 1991-2020.
Sweet onions or onions that keep
Here’s the trade-off every onion grower eventually runs into: sweetness and storage life pull in opposite directions, and it isn’t luck, it’s chemistry. The bite in a pungent onion comes from volatile sulfur compounds, and those same compounds are what protect the bulb once it’s cured and sitting in a pantry. A sweet variety simply has fewer of them. That makes it better sliced raw on a sandwich in July, and it also means it will not last through winter no matter how carefully it’s cured. The University of Missouri Extension puts it plainly: sweet onions do not store as well as the more pungent types.
That chemistry lines up with the day-length pattern already covered. Short-day types, grown mostly in the South, tend to run sweeter. Long-day types, suited to New York’s latitude, tend to run sharper and keep longer. Since New York sits mostly in long-day and intermediate-day territory, the realistic harvest here leans toward onions that hold up in storage rather than the mild, syrupy bulbs Southern gardens are known for.
That doesn’t mean every New York onion is a storage onion. Walla Walla Sweet is a long-day variety bred specifically for sweetness and short storage life, and it’s on the list of varieties that bulb here. Choosing it means eating your onions within a few weeks of harvest, not stacking them in a cellar. Varieties like Patterson, Ailsa Craig, or Bridger, all long-day and all on the list, trade some of that sweetness for a bulb that will still be sound in March.
The practical move for a New York garden is to grow both: a sweet variety for summer eating, and a pungent, long-day keeper for the pantry. What you shouldn’t do is expect one variety to give you both, no onion, anywhere, manages that.