When to plant Onions in Montana
In spring, from Apr 1 – May 1 in Billings to May 10 – June 10 in Butte-Silver Bow (balance).
In fall, May 1 – June 10.
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 |
|---|---|---|
| Belgrade | May 1 – 30 | Spring-planted |
| Billings | Apr 1 – May 1 | Spring-planted |
| Bozeman | May 1 – 30 | Spring-planted |
| Butte-Silver Bow (balance) | May 10 – June 10 | May 1 – June 10 |
| Great Falls | Apr 10 – May 1 | Spring-planted |
| Helena | Apr 10 – May 1 | Spring-planted |
| Kalispell | May 1 – 30 | May 1 – June 10 |
| Missoula | Apr 10 – 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.