FrostCal

When to Plant Onions in Arizona

In a typical Arizona location, start seeds indoors Dec 5 – Dec 19, then transplant outdoors Jan 16 – Jan 30. Across the state, the outdoor planting window starts as early as Dec 7 in Bullhead City and as late as May 7 in Flagstaff. 3 cities in Arizona are essentially frost-free and can plant on a year-round schedule.

Method Start indoors, then transplant
Days to maturity 90–120 days

Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Onions Planting Dates by City

CityStart indoorsTransplant
PhoenixOct 27 – Nov 10Dec 8 – Dec 22
TucsonNov 11 – Nov 25Dec 23 – Jan 6
MesaDec 5 – Dec 19Jan 16 – Jan 30
ChandlerDec 5 – Dec 19Jan 16 – Jan 30
GilbertDec 5 – Dec 19Jan 16 – Jan 30
GlendaleNov 11 – Nov 25Dec 23 – Jan 6
ScottsdaleDec 5 – Dec 19Jan 16 – Jan 30
PeoriaNov 11 – Nov 25Dec 23 – Jan 6
TempeDec 5 – Dec 19Jan 16 – Jan 30
Tempe JunctionDec 5 – Dec 19Jan 16 – Jan 30
SurpriseNov 11 – Nov 25Dec 23 – Jan 6
YumaOct 30 – Nov 13Dec 11 – Dec 25
San Tan ValleyNov 23 – Dec 7Jan 4 – Jan 18
AvondaleOct 29 – Nov 12Dec 10 – Dec 24
GoodyearOct 29 – Nov 12Dec 10 – Dec 24
FlagstaffMar 26 – Apr 9May 7 – May 21
Casas AdobesDec 18 – Jan 1Jan 29 – Feb 12
Lake Havasu CityOct 27 – Nov 10Dec 8 – Dec 22
Casa GrandeNov 27 – Dec 11Jan 8 – Jan 22
BuckeyeOct 29 – Nov 12Dec 10 – Dec 24
Catalina FoothillsDec 12 – Dec 26Jan 23 – Feb 6
MaricopaDec 15 – Dec 29Jan 26 – Feb 9
Oro ValleyJan 22 – Feb 5Mar 5 – Mar 19
Sierra VistaJan 25 – Feb 8Mar 8 – Mar 22
Prescott ValleyFeb 9 – Feb 23Mar 23 – Apr 6
PrescottFeb 19 – Mar 5Apr 2 – Apr 16
MaranaDec 15 – Dec 29Jan 26 – Feb 9
Bullhead CityOct 26 – Nov 9Dec 7 – Dec 21
Apache JunctionDec 3 – Dec 17Jan 14 – Jan 28
Sun CityNov 11 – Nov 25Dec 23 – Jan 6

Showing the 30 most populous of 72 Arizona cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Arizona cities.

Frequently Asked Questions

When should I plant onions in Arizona?

In a typical Arizona location, start seeds indoors Dec 5 – Dec 19, then transplant outdoors Jan 16 – Jan 30. Across the state, the outdoor planting window starts as early as Dec 7 in Bullhead City and as late as May 7 in Flagstaff. 3 cities in Arizona are essentially frost-free and can plant on a year-round schedule.

When is the last frost in Arizona?

The average last spring frost in Arizona ranges from January 4 in Bullhead City to June 4 in Flagstaff, based on NOAA 1991–2020 climate normals.

How long do onions take to grow?

Onions typically take 90–120 days from planting to harvest. Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Other Crops in Arizona

When to plant onions in other states

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