When to plant Onions in Colorado
In spring, from Mar 1 – Apr 1 in Grand Junction to May 10 – June 10 in Steamboat Springs.
In fall, May 1 – June 10 in Steamboat Springs.
Dates are for setting out plants. USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.
| Place | Spring | Fall |
|---|---|---|
| Arvada | Apr 1 – May 1 | Spring-planted |
| Aurora | Apr 10 – May 1 | Spring-planted |
| Berthoud | Apr 10 – May 1 | Spring-planted |
| Boulder | Apr 10 – May 1 | Spring-planted |
| Brighton | Apr 1 – May 1 | Spring-planted |
| Broomfield | Apr 1 – May 1 | Spring-planted |
| Cañon City | Apr 1 – May 1 | Spring-planted |
| Castle Pines | Apr 10 – May 1 | Spring-planted |
| Castle Rock | Apr 10 – May 1 | Spring-planted |
| Centennial | Apr 1 – May 1 | Spring-planted |
| Colorado Springs | Apr 1 – May 1 | Spring-planted |
| Commerce City | Apr 1 – May 1 | Spring-planted |
| Denver | Apr 1 – May 1 | Spring-planted |
| Durango | Apr 20 – May 15 | Spring-planted |
| Englewood | Apr 1 – May 1 | Spring-planted |
| Erie | Apr 10 – May 1 | Spring-planted |
| Evans | Apr 1 – May 1 | Spring-planted |
| Federal Heights | Apr 1 – May 1 | Spring-planted |
| Firestone | Apr 10 – May 1 | Spring-planted |
| Fort Collins | Apr 1 – May 1 | Spring-planted |
| Fort Morgan | Apr 10 – May 1 | Spring-planted |
| Fountain | Apr 1 – May 1 | Spring-planted |
| Frederick | Apr 10 – May 1 | Spring-planted |
| Fruita | Apr 1 – May 1 | Spring-planted |
| Glenwood Springs | Apr 10 – May 1 | Spring-planted |
| Golden | Apr 1 – May 1 | Spring-planted |
| Grand Junction | Mar 1 – Apr 1 | Spring-planted |
| Greeley | Apr 1 – May 1 | Spring-planted |
| Greenwood Village | Apr 10 – May 1 | Spring-planted |
| Johnstown | Apr 10 – May 1 | Spring-planted |
| Lafayette | Apr 1 – May 1 | Spring-planted |
| Lakewood | Apr 1 – May 1 | Spring-planted |
| Littleton | Apr 1 – May 1 | Spring-planted |
| Lone Tree | Apr 1 – May 1 | Spring-planted |
| Longmont | Apr 10 – May 1 | Spring-planted |
| Louisville | Apr 10 – May 1 | Spring-planted |
| Loveland | Apr 10 – May 1 | Spring-planted |
| Montrose | Apr 1 – May 1 | Spring-planted |
| Monument | Apr 20 – May 15 | Spring-planted |
| Northglenn | Apr 1 – May 1 | Spring-planted |
| Parker | Apr 10 – May 1 | Spring-planted |
| Pueblo | Apr 1 – May 1 | Spring-planted |
| Rifle | Apr 10 – May 1 | Spring-planted |
| Severance | Apr 1 – May 1 | Spring-planted |
| Steamboat Springs | May 10 – June 10 | May 1 – June 10 |
| Sterling | Apr 1 – May 1 | Spring-planted |
| Superior | Apr 10 – May 1 | Spring-planted |
| Thornton | Apr 1 – May 1 | Spring-planted |
| Timnath | Apr 1 – May 1 | Spring-planted |
| Wellington | Apr 1 – May 1 | Spring-planted |
| Westminster | Apr 1 – May 1 | Spring-planted |
| Wheat Ridge | Apr 1 – May 1 | Spring-planted |
| Windsor | Apr 1 – May 1 | Spring-planted |
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), tables 4 and 5. Frost dates: NOAA U.S. Climate Normals 1991–2020. “—” means the place's frost date is outside the table. The full USDA table for onion plants.