FrostCal

When to Plant Onions in Wyoming

In a typical Wyoming location, start seeds indoors Mar 8 – Mar 22, then transplant outdoors Apr 19 – May 3. Across the state, the outdoor planting window starts as early as Apr 6 in Worland and as late as May 15 in Evanston. 1 city in Wyoming is 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
CheyenneMar 5 – Mar 19Apr 16 – Apr 30
CasperMar 1 – Mar 15Apr 12 – Apr 26
GilletteMar 6 – Mar 20Apr 17 – May 1
LaramieMar 29 – Apr 12May 10 – May 24
Rock SpringsMar 15 – Mar 29Apr 26 – May 10
SheridanMar 12 – Mar 26Apr 23 – May 7
Green RiverMar 15 – Mar 29Apr 26 – May 10
EvanstonApr 3 – Apr 17May 15 – May 29
RivertonMar 3 – Mar 17Apr 14 – Apr 28
JacksonFrost-free: year-round planting
CodyMar 3 – Mar 17Apr 14 – Apr 28
RawlinsMar 8 – Mar 22Apr 19 – May 3
LanderMar 9 – Mar 23Apr 20 – May 4
TorringtonMar 2 – Mar 16Apr 13 – Apr 27
DouglasMar 10 – Mar 24Apr 21 – May 5
PowellMar 10 – Mar 24Apr 21 – May 5
RanchettesMar 3 – Mar 17Apr 14 – Apr 28
WorlandFeb 23 – Mar 9Apr 6 – Apr 20
BuffaloMar 15 – Mar 29Apr 26 – May 10
South GreeleyMar 5 – Mar 19Apr 16 – Apr 30

Showing the 20 most populous of 20 Wyoming cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Wyoming cities.

Frequently Asked Questions

When should I plant onions in Wyoming?

In a typical Wyoming location, start seeds indoors Mar 8 – Mar 22, then transplant outdoors Apr 19 – May 3. Across the state, the outdoor planting window starts as early as Apr 6 in Worland and as late as May 15 in Evanston. 1 city in Wyoming is essentially frost-free and can plant on a year-round schedule.

When is the last frost in Wyoming?

The average last spring frost in Wyoming ranges from May 4 in Worland to June 12 in Evanston, 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 Wyoming

When to plant onions in other states

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