When to plant · 202 cities · zones 8a–11a

When to plant onions in California

Start Spanish Onion seeds indoors around Nov 15 and transplant around Jan 10 — the California statewide median, counted from a last spring frost of Feb 7 across 1,426 ZIP codes and 311 NOAA stations.

Nov 15Start indoors12 weeks before last frost

Jan 10Plant outDec 8 – Apr 6 across the state

Feb 7Last spring frostmedian · 1 in 10 years after Mar 12

Apr 30First harvest110 days from transplant

The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.

124 of these California cities sit below 36° N, where a long-day onion never gets the day length to bulb. They are flagged in the table; plant a short-day type there.

Build a plan from your ZIP →California frost dates by city →

California onions, by step

Statewide median last frost Feb 7, first fall frost Dec 7, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.

Cultivar	Start indoors	Plant out	First harvest	Days
Spanish OnionYellow Sweet Spanish (long-day)	Nov 15	Jan 10	Apr 30	110 from transplant

Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station California's ZIP codes resolve to; 375 of 1,801 ZIPs have no datable freeze and are left out.

Onions in California, city by city

Spanish Onion, scheduled from each city's nearest NOAA station — the same dates as its frost page.

City	Last frost	Start indoors	Plant out	First harvest
Los Angeleszone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
San Diegozone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
San Josezone 9b	Jan 2	Oct 10	Dec 5	Mar 25
Fresnozone 9b	Jan 14	Oct 22	Dec 17	Apr 6
Sacramentozone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Long Beachzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Oaklandzone 10a	frost rare	Nov 8	Jan 3	Apr 23
Bakersfieldzone 9bbelow 36° N · short-day onion	Jan 31	Nov 8	Jan 3	Apr 23
Anaheimzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Stocktonzone 9b	Feb 5	Nov 13	Jan 8	Apr 28
Riversidezone 10abelow 36° N · short-day onion	Jan 9	Oct 17	Dec 12	Apr 1
Irvinezone 10abelow 36° N · short-day onion	Jan 5	Oct 13	Dec 8	Mar 28
Santa Anazone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Chula Vistazone 10bbelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Santa Claritazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Fremontzone 10a	Jan 1	Oct 9	Dec 4	Mar 24
San Bernardinozone 10abelow 36° N · short-day onion	May 5	Feb 10	Apr 7	Jul 26
Modestozone 9b	Jan 31	Nov 8	Jan 3	Apr 23
Fontanazone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Moreno Valleyzone 9bbelow 36° N · short-day onion	Jan 10	Oct 18	Dec 13	Apr 2
Oxnardzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Huntington Beachzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Glendalezone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Ontariozone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Elk Grovezone 9b	Feb 2	Nov 10	Jan 5	Apr 25
Santa Rosazone 9a	Feb 25	Dec 3	Jan 28	May 18
Rancho Cucamongazone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Garden Grovezone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Oceansidezone 10abelow 36° N · short-day onion	Jan 23	Oct 31	Dec 26	Apr 15
Lancasterzone 8abelow 36° N · short-day onion	Apr 3	Jan 9	Mar 6	Jun 24
Rosevillezone 9b	Feb 25	Dec 3	Jan 28	May 18
Palmdalezone 8bbelow 36° N · short-day onion	Mar 10	Dec 16	Feb 10	May 31
Coronazone 10abelow 36° N · short-day onion	Jan 17	Oct 25	Dec 20	Apr 9
Salinaszone 9b	Jan 29	Nov 6	Jan 1	Apr 21
Haywardzone 10a	Jan 2	Oct 10	Dec 5	Mar 25
Sunnyvalezone 10a	Jan 6	Oct 14	Dec 9	Mar 29
Escondidozone 10abelow 36° N · short-day onion	Jan 2	Oct 10	Dec 5	Mar 25
Pomonazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Visaliazone 9b	Jan 23	Oct 31	Dec 26	Apr 15
Victorvillezone 8bbelow 36° N · short-day onion	Mar 18	Dec 24	Feb 18	Jun 8
Fullertonzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Torrancezone 10bbelow 36° N · short-day onion	Jan 9	Oct 17	Dec 12	Apr 1
Orangezone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Pasadenazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Santa Clarazone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Cloviszone 9b	Jan 14	Oct 22	Dec 17	Apr 6
Simi Valleyzone 10abelow 36° N · short-day onion	Jan 24	Nov 1	Dec 27	Apr 16
Thousand Oakszone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Concordzone 9b	Jan 9	Oct 17	Dec 12	Apr 1
Vallejozone 9b	Mar 5	Dec 11	Feb 5	May 26
Fairfieldzone 9b	Jan 15	Oct 23	Dec 18	Apr 7
Berkeleyzone 10a	Jan 3	Oct 11	Dec 6	Mar 26
Antiochzone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Menifeezone 9bbelow 36° N · short-day onion	Jan 28	Nov 5	Dec 31	Apr 20
Richmondzone 10a	Jan 4	Oct 12	Dec 7	Mar 27
Carlsbadzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Murrietazone 9bbelow 36° N · short-day onion	Feb 2	Nov 10	Jan 5	Apr 25
Temeculazone 9bbelow 36° N · short-day onion	Feb 2	Nov 10	Jan 5	Apr 25
Santa Mariazone 9bbelow 36° N · short-day onion	Feb 4	Nov 12	Jan 7	Apr 27
San Buenaventura (Ventura)zone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Downeyzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Costa Mesazone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Jurupa Valleyzone 10abelow 36° N · short-day onion	Jan 9	Oct 17	Dec 12	Apr 1
West Covinazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Rialtozone 10abelow 36° N · short-day onion	Jan 10	Oct 18	Dec 13	Apr 2
El Montezone 10bbelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Vacavillezone 9b	Feb 18	Nov 26	Jan 21	May 11
Burbankzone 10abelow 36° N · short-day onion	Jan 2	Oct 10	Dec 5	Mar 25
El Cajonzone 10abelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
San Mateozone 10a	frost rare	Nov 8	Jan 3	Apr 23
Chicozone 9b	Mar 4	Dec 10	Feb 4	May 25
Inglewoodzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Hesperiazone 8bbelow 36° N · short-day onion	May 5	Feb 10	Apr 7	Jul 26
Daly Cityzone 10a	frost rare	Nov 8	Jan 3	Apr 23
Tracyzone 9b	Jan 19	Oct 27	Dec 22	Apr 11
Vistazone 10abelow 36° N · short-day onion	Jan 30	Nov 7	Jan 2	Apr 22
Norwalkzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
San Marcoszone 10abelow 36° N · short-day onion	Jan 2	Oct 10	Dec 5	Mar 25
Mercedzone 9a	Mar 3	Dec 9	Feb 3	May 24
Mantecazone 9b	Feb 6	Nov 14	Jan 9	Apr 29
Indiozone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Chinozone 9bbelow 36° N · short-day onion	Jan 17	Oct 25	Dec 20	Apr 9
Reddingzone 9a	Mar 3	Dec 9	Feb 3	May 24
Hemetzone 9bbelow 36° N · short-day onion	Jan 31	Nov 8	Jan 3	Apr 23
Mission Viejozone 10bbelow 36° N · short-day onion	Jan 5	Oct 13	Dec 8	Mar 28
Carsonzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Comptonzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
South Gatezone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Santa Monicazone 11abelow 36° N · short-day onion	frost rare	Oct 23	Dec 18	Apr 7
Westminsterzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Folsomzone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Mountain Viewzone 9b	Jan 6	Oct 14	Dec 9	Mar 29
Santa Barbarazone 10bbelow 36° N · short-day onion	Jan 13	Oct 21	Dec 16	Apr 5
Lake Forestzone 10bbelow 36° N · short-day onion	Jan 5	Oct 13	Dec 8	Mar 28
Citrus Heightszone 9b	Jan 12	Oct 20	Dec 15	Apr 4
San Leandrozone 10a	Jan 7	Oct 15	Dec 10	Mar 30
San Ramonzone 9b	Feb 15	Nov 23	Jan 18	May 8
Whittierzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Livermorezone 9b	Feb 15	Nov 23	Jan 18	May 8
Rancho Cordovazone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Hawthornezone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Perriszone 9bbelow 36° N · short-day onion	Jan 10	Oct 18	Dec 13	Apr 2
Redwood Cityzone 10a	Jan 17	Oct 25	Dec 20	Apr 9
Newport Beachzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Buena Parkzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Alhambrazone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Milpitaszone 10a	Jan 12	Oct 20	Dec 15	Apr 4
Uplandzone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Tustinzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Alamedazone 10a	Jan 7	Oct 15	Dec 10	Mar 30
Lakewoodzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Chino Hillszone 10abelow 36° N · short-day onion	Jan 17	Oct 25	Dec 20	Apr 9
Pittsburgzone 9b	Jan 9	Oct 17	Dec 12	Apr 1
Napazone 9b	Feb 12	Nov 20	Jan 15	May 5
Bellflowerzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Pleasantonzone 9b	Feb 15	Nov 23	Jan 18	May 8
Rocklinzone 9b	Feb 25	Dec 3	Jan 28	May 18
Apple Valleyzone 8bbelow 36° N · short-day onion	Mar 18	Dec 24	Feb 18	Jun 8
Redlandszone 10abelow 36° N · short-day onion	Jan 27	Nov 4	Dec 30	Apr 19
Lake Elsinorezone 9bbelow 36° N · short-day onion	Jan 28	Nov 5	Dec 31	Apr 20
Turlockzone 9b	Jan 6	Oct 14	Dec 9	Mar 29
Tularezone 9b	Jan 23	Oct 31	Dec 26	Apr 15
Walnut Creekzone 9b	Mar 8	Dec 14	Feb 8	May 29
Eastvalezone 10abelow 36° N · short-day onion	Jan 17	Oct 25	Dec 20	Apr 9
Dublinzone 9b	Feb 15	Nov 23	Jan 18	May 8
Camarillozone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Baldwin Parkzone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Yuba Cityzone 9b	Feb 11	Nov 19	Jan 14	May 4
Maderazone 9b	Feb 12	Nov 20	Jan 15	May 5
Lodizone 9b	Feb 9	Nov 17	Jan 12	May 2
Redondo Beachzone 11abelow 36° N · short-day onion	frost rare	Oct 23	Dec 18	Apr 7
Palo Altozone 9b	Feb 1	Nov 9	Jan 4	Apr 24
Daviszone 9b	Feb 10	Nov 18	Jan 13	May 3
Yorba Lindazone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Brentwoodzone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Union Cityzone 9b	Jan 2	Oct 10	Dec 5	Mar 25
South San Franciscozone 10a	frost rare	Nov 8	Jan 3	Apr 23
Laguna Niguelzone 10bbelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Lynwoodzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Portervillezone 9b	Feb 20	Nov 28	Jan 23	May 13
Woodlandzone 9b	Feb 7	Nov 15	Jan 10	Apr 30
San Clementezone 10bbelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Santa Cruzzone 9b	Jan 29	Nov 6	Jan 1	Apr 21
La Habrazone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Encinitaszone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
La Mesazone 10bbelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Montebellozone 10bbelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Hanfordzone 9a	Feb 7	Nov 15	Jan 10	Apr 30
Gilroyzone 9b	Feb 24	Dec 2	Jan 27	May 17
San Rafaelzone 10a	Jan 11	Oct 19	Dec 14	Apr 3
Beaumontzone 9bbelow 36° N · short-day onion	Jan 31	Nov 8	Jan 3	Apr 23
Petalumazone 9b	Feb 28	Dec 6	Jan 31	May 21
Pico Riverazone 10bbelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Santeezone 10abelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Gardenazone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Cupertinozone 9b	Mar 21	Dec 27	Feb 21	Jun 11
National Cityzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Monterey Parkzone 10bbelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Highlandzone 10abelow 36° N · short-day onion	Jan 27	Nov 4	Dec 30	Apr 19
Lincolnzone 9a	Feb 25	Dec 3	Jan 28	May 18
Fountain Valleyzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
West Sacramentozone 9b	Feb 2	Nov 10	Jan 5	Apr 25
San Jacintozone 9bbelow 36° N · short-day onion	Jan 31	Nov 8	Jan 3	Apr 23
Arcadiazone 10abelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Yucaipazone 9bbelow 36° N · short-day onion	Jan 27	Nov 4	Dec 30	Apr 19
Coltonzone 10abelow 36° N · short-day onion	Jan 10	Oct 18	Dec 13	Apr 2
Placentiazone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Delanozone 9bbelow 36° N · short-day onion	Jan 31	Nov 8	Jan 3	Apr 23
Palm Desertzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Cathedral Cityzone 10abelow 36° N · short-day onion	Jan 9	Oct 17	Dec 12	Apr 1
Novatozone 9b	Jan 11	Oct 19	Dec 14	Apr 3
Diamond Barzone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Huntington Parkzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Watsonvillezone 9b	Jan 31	Nov 8	Jan 3	Apr 23
Paramountzone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Aliso Viejozone 10bbelow 36° N · short-day onion	Jan 6	Oct 14	Dec 9	Mar 29
Glendorazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
San Luis Obispozone 9bbelow 36° N · short-day onion	Jan 16	Oct 24	Dec 19	Apr 8
Rosemeadzone 10bbelow 36° N · short-day onion	Jan 4	Oct 12	Dec 7	Mar 27
Powayzone 10abelow 36° N · short-day onion	Mar 4	Dec 10	Feb 4	May 25
Cypresszone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Cereszone 9b	Jan 31	Nov 8	Jan 3	Apr 23
Covinazone 10abelow 36° N · short-day onion	Jan 8	Oct 16	Dec 11	Mar 31
Los Banoszone 9a	Jan 26	Nov 3	Dec 29	Apr 18
Azusazone 10abelow 36° N · short-day onion	Apr 28	Feb 3	Mar 31	Jul 19
Breazone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Oakleyzone 9b	Jan 12	Oct 20	Dec 15	Apr 4
Cerritoszone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
La Miradazone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Rancho Santa Margaritazone 10bbelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23
Newarkzone 10a	Jan 1	Oct 9	Dec 4	Mar 24
Morgan Hillzone 9b	Feb 24	Dec 2	Jan 27	May 17
Palm Springszone 10abelow 36° N · short-day onion	Jan 9	Oct 17	Dec 12	Apr 1
Coachellazone 10abelow 36° N · short-day onion	Feb 7	Nov 15	Jan 10	Apr 30
Hollisterzone 9b	Feb 19	Nov 27	Jan 22	May 12
Rohnert Parkzone 9a	Feb 28	Dec 6	Jan 31	May 21
El Centrozone 10abelow 36° N · short-day onion	Jan 3	Oct 11	Dec 6	Mar 26
Lompoczone 10abelow 36° N · short-day onion	Jan 20	Oct 28	Dec 23	Apr 12
Danvillezone 9b	Mar 8	Dec 14	Feb 8	May 29
Campbellzone 9b	Feb 2	Nov 10	Jan 5	Apr 25
San Brunozone 10a	Jan 11	Oct 19	Dec 14	Apr 3
Stantonzone 10abelow 36° N · short-day onion	frost rare	Nov 8	Jan 3	Apr 23

What these onions become

Sunday GravyTwelve pounds of paste tomatoes, three hours, and a food mill instead of a peeling job. The reduction that makes a homegrown tomato taste like the reason you grew it.Recipe and process →Salsa VerdeBlistered tomatillos, serrano, and a fistful of cilantro. Naturally acidic, ready in forty minutes, and it clings to a taco because tomatillos bring their own pectin.Recipe and process →Chipotles en AdoboRed jalapeños, eight hours of cold smoke, then a braise in a dark ancho-and-vinegar sauce. The single most useful jar in a kitchen.Recipe and process →Habanero-Carrot Hot SauceThree weeks in a 3% brine turns raw habanero heat into something layered and sour, and carrot gives it body and colour with no thickener. The reference build for a homegrown hot sauce.Recipe and process →

What California onions need

SeedsThe cultivar decides the sauce. Everything downstream is damage control.

Yellow Sweet Spanish Onion Seed
A long-day storage onion with enough sugar to sweat down without scorching. The aromatic base under every tomato sauce on this site.
Amazon · paid link ↗

StartSoil temperature and light intensity, indoors, weeks before your frost date.

Organic Seed Starter Potting MixMust have
Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.
Amazon · paid link ↗
72-Cell Trays with 1020 Bottoms, 5-PackMust have
The cheap black nursery trays crack after one season and flex enough to break roots when you lift them. These do not. Over five seasons the price per use is lower than the throwaways.
Amazon · paid link ↗
T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have
A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.
Amazon · paid link ↗

GrowRoot volume, nutrition and structure. Where most home crops actually fail.

Rapitest Soil Test Kit
In-ground growers are guessing until they test. pH outside 6.0–6.8 locks nutrients out no matter how much fertiliser you add, and no amount of feeding fixes that.
Amazon · paid link ↗
Pure Organic Worm Castings, 15 lb
Not a fertiliser so much as a soil-biology inoculant with a mild nutrient charge. A cup in each planting hole is a cheap, unglamorous improvement you can measure by August.
Amazon · paid link ↗

HarvestTiming, handling, and weighing what you actually got.

Garden Harvest Basket with Tool Caddy
A harvest basket that doubles as a colander means the hose rinse happens in the garden, and the dirt stays outside. On a 20-pound tomato day that is a genuine time saving.
Amazon · paid link ↗

Paid links. We earn a commission from Amazon if you buy; you pay the same. Disclosure.

Onions in California: questions

When should I plant onions in California?

Transplant around Jan 10 at the statewide median; across the state that date runs from Dec 8 in the warmest tenth of California's ZIP codes to Apr 6 in the coldest. To cut the freeze risk to one year in ten, count from Mar 12 instead of the median last frost. Use the city table for your own town.

When do I start onions seeds indoors in California?

Around Nov 15 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.

When is the last frost in California?

The ZIP-weighted median of NOAA 1991–2020 station medians is Feb 7. In the warmest tenth of California's ZIP codes the median last frost falls on or before Jan 5; in the coldest tenth, on or after May 4.

When will California onions be ready to harvest?

Spanish Onion planted on the statewide date is ready around Apr 30: 110 days from transplant.

Which onions grow in California?

Spanish Onion is a long-day onion: it bulbs at 14–16 hours of daylight, which it gets above roughly 36° N. 124 of the 202 California cities listed here sit below that line; grow a short-day onion there.

More for California

Onions in every state → · California frost dates → · How frost-date math works →