California sits at 33.94 degrees north latitude, based on the Los Angeles weather station, and gets 14 hours and 16 minutes of daylight on the longest day of the year. That day length lands the state squarely in intermediate-day and short-day onion territory. Long-day varieties, the kind grown across most of the northern United States, are the wrong choice here.
The short answer for California
An onion bulbs when day length crosses its genetic trigger, not when the weather warms up. Short-day types start bulbing around 12 hours of daylight; intermediate-day types wait for something closer to 13 to 14 hours; long-day types hold off until 14 to 16 hours. At 14 hours 16 minutes on the summer solstice, Los Angeles barely clears the short-day threshold and sits well within the intermediate-day range. That’s the group California gardeners should be shopping from.
Within the varieties documented on this site, twelve have published latitude ranges that cover 33.94N. The intermediate-day options are Candy (33-40N), Elsye (32-45N), Expression (32-45N), Scout (32-46N), and Sierra Blanca (32-45N). The short-day options are Red Sensation (25-35N), Texas Grano 1015Y (25-35N), and Vidora (25-35N), along with three others that don’t have their own page on this site yet but are worth naming for completeness: Gabriella (20-35N), Madalyn (20-35N), Red Rock (30-36N), and White Castle (30-38N).
That’s a wide enough field that most California gardeners can pick based on flavor and storage life rather than worrying whether the variety will bulb at all. The real work is knowing which varieties to leave off the shopping list entirely.
What will not work here
Thirteen varieties documented on this site have published ranges that start north of 33.94N. Plant one of these in a California garden and the result isn’t a smaller onion. It’s no onion. The plant reads the day length, never gets the signal it needs, and keeps making leaves instead of switching to bulb production. By the time summer heat and the plant’s own exhaustion catch up with it, what’s left is a floppy green top and a rotting stub at the base, not something you’d want on a cutting board.
- Ailsa Craig (long-day, 38-60N), needs daylight California’s longest day never reaches
- Barolo (long-day, 38-55N), bulbing threshold too high for this latitude
- Blush (long-day, 38-55N), same problem, further north than California’s day length supports
- Frontier (long-day, 40-50N), built for latitudes with much longer summer days
- New York Early (long-day, 38-50N), the name says it all; wrong hemisphere of the state map
- Patterson (long-day, 38-55N), a northern storage onion, out of range here
- Powell (long-day, 43-47N), needs a day length California doesn’t get
- Red Carpet (long-day, 40-45N), bred for a much higher latitude band
- Red Long of Florence (intermediate-day, 38-50N), even as an intermediate type, its range starts above California’s reference latitude
- Redwing (long-day, 43-65N), one of the most northern ranges on the list
- Rossa di Milano (long-day, 38-50N), won’t trigger at California’s day length
- Safrane (long-day, 42-50N), needs a summer solstice well past 14h16
- Talon (long-day, 42-50N), same story, wrong latitude band entirely
None of these are marginal cases. Their published ranges start above 33.94N with room to spare, so there’s no need to hedge with “may struggle.” They simply don’t belong in a California onion bed.
What changes across California
California is not a single latitude. The state runs from around 32.5 degrees north near the Mexican border to roughly 42 degrees north at the Oregon line, a spread of close to ten degrees. The 33.94N figure comes from the Los Angeles station, which represents Southern California well but says little about Redding, Yreka, or the Oregon border towns, where summer days run measurably longer.
| Region | Approx. latitude | Summer daylight vs. reference | What it changes |
|---|---|---|---|
| Southern California (San Diego to L.A. basin) | ~32.5-34N | About the same as reference (14h16) | Short-day and intermediate-day varieties are the safe choice |
| Central Valley and Central Coast | ~35-37N | Noticeably longer | The blurred-zone varieties become plausible, not just intermediate-day types |
| Far Northern California | ~40-42N | Longer still | Some long-day varieties with ranges starting near 38-40N move into reach |
Six varieties fall into that blurred middle zone, within a degree and a half of a published boundary: Bridger (long-day, 35-50N), Cabernet (intermediate-day, 35-45N), Calibra (intermediate-day, 35-45N), Monastrell (intermediate-day, 35-46N), Red Long of Tropea (intermediate-day, 35-48N), and Walla Walla Sweet (long-day, 35-55N). A gardener in the Central Valley or points north might get a decent bulb from one of these. A gardener in the Los Angeles basin or San Diego almost certainly won’t. These ranges are a continuum, not a hard line, so treat this list as “worth a trial” rather than “guaranteed,” and expect results to vary from one growing season to the next.
Sweet now, or onions that last
The chemistry behind onion flavor is also what decides how long an onion sits in a pantry without going soft. The bite in a pungent onion comes from volatile sulfur compounds, and those same compounds work as a natural preservative. Fewer of them means a milder onion on the cutting board, but also a shorter shelf life. According to University of Missouri Extension, “as a rule, ‘sweet’ onions do not store as well as the more pungent types,” and that rule holds regardless of where the onion was grown.
Short-day varieties, the ones best suited to Southern California’s day length, tend to run sweeter and milder. That’s genuinely good news at the dinner table in June and July, but it means the harvest doesn’t hold. A Texas Grano 1015Y or a Vidora eaten fresh off the vine in early summer is a different food than the same variety three months later, soft and starting to sprout in a kitchen drawer.
Intermediate-day varieties split the difference. Candy, Scout, and Sierra Blanca carry a bit more sulfur than the sweetest short-day types, which buys some extra weeks in storage without losing all the mildness that makes home-grown onions worth the garden space in the first place.
What that means for a California pantry in March: mostly empty, unless the summer harvest leaned toward the intermediate-day varieties and was cured and stored properly. A garden built entirely around sweet short-day onions gives a great July and August, then nothing left by winter. Anyone who wants onions on hand into late winter should plant at least a row of an intermediate-day variety alongside the sweeter picks, and cure the harvest fully before it goes into storage.
Checking this against your own garden
Every figure in this article is anchored to one station near Los Angeles at 33.94 degrees north. That’s a reasonable stand-in for most of coastal and Southern California, but it stops being accurate the further a garden sits from that point, especially north into the Central Valley or the far north of the state.
- Look up your own latitude if you’re gardening north of the Bay Area or in the far north of the state; a difference of two or three degrees can shift you into or out of a variety’s published range
- Check your local average last-frost and first-frost dates, since onion transplants and sets need to go in on a schedule tied to your own frost window, not a statewide average
- Contact your county’s UC Cooperative Extension office for planting windows and variety trials specific to your growing region
- Watch your own summer solstice day length if you’re near a stated boundary, since a few extra minutes of daylight is exactly what separates “bulbs reliably” from “makes leaves and rots”
A single state figure can point a gardener in the right general direction. It can’t replace a look at the actual conditions outside the back door.