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When to plant onion in Wyoming

Wyoming spans USDA zones 4a–5b, so the right time to plant onion shifts by weeks across the state. The window to transplant seedlings outdoors runs from about April 12 in Casper to May 23 in Jackson — below are local dates for 11 cities, each computed from its own frost dates.

In Cheyennethe onion transplant out window (April 16–April 30) has passed for this year.
CityZoneLast frostFirst frostTransplant out
Cheyenne5bMay 14October 1April 16 – April 30
Casper5aMay 10September 29April 12 – April 26
Gillette4bMay 15October 1April 17 – May 1
Laramie4aJune 7September 4May 10 – May 24
Rock Springs5aMay 24September 24April 26 – May 10
Sheridan5aMay 21September 23April 23 – May 7
Evanston5aJune 12September 12May 15 – May 29
Green River5aMay 24September 22April 26 – May 10

Onion in Wyoming: FAQ

When can I plant onion in Wyoming?

Across Wyoming, the time to transplant onion spans roughly April 12 in Casper to May 23 in Jackson, each following that city's local frost dates.

Does the onion planting date vary across Wyoming?

Yes. Wyoming publishes 11 cities with their own frost dates, so the right onion planting window shifts by weeks between the warmest and coldest parts of the state — use your city's page for the exact dates.

How long does onion take to grow in Wyoming?

Onion takes about 90–110 days to reach harvest once planted — check that this fits inside your city's frost-free season on its place page.

Planting reminders

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An email when it’s time to start seeds, transplant, and sow — timed to your frost dates. Double opt-in, one-click unsubscribe, no spam.

Onion planting guide →All Wyoming cities →Wyoming planting calendar →
When to Plant Onion in Wyoming — Frost-Based Dates by City — BlissGarden