When to Plant Onions in Montana
In a typical Montana location, start seeds indoors Mar 5 – Mar 19, then transplant outdoors Apr 16 – Apr 30. Across the state, the outdoor planting window starts as early as Apr 7 in Laurel and as late as May 16 in Butte.
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
| City | Start indoors | Transplant |
|---|---|---|
| Billings | Mar 1 – Mar 15 | Apr 12 – Apr 26 |
| Missoula | Mar 1 – Mar 15 | Apr 12 – Apr 26 |
| Great Falls | Feb 25 – Mar 11 | Apr 8 – Apr 22 |
| Bozeman | Mar 17 – Mar 31 | Apr 28 – May 12 |
| Butte | Apr 4 – Apr 18 | May 16 – May 30 |
| Helena | Feb 28 – Mar 14 | Apr 11 – Apr 25 |
| Kalispell | Mar 22 – Apr 5 | May 3 – May 17 |
| Havre | Mar 6 – Mar 20 | Apr 17 – May 1 |
| Anaconda | Mar 23 – Apr 6 | May 4 – May 18 |
| Miles City | Feb 27 – Mar 13 | Apr 10 – Apr 24 |
| Helena Valley Southeast | Feb 28 – Mar 14 | Apr 11 – Apr 25 |
| Belgrade | Mar 17 – Mar 31 | Apr 28 – May 12 |
| Helena Valley West Central | Feb 28 – Mar 14 | Apr 11 – Apr 25 |
| Evergreen | Mar 22 – Apr 5 | May 3 – May 17 |
| Livingston | Mar 18 – Apr 1 | Apr 29 – May 13 |
| Whitefish | Mar 7 – Mar 21 | Apr 18 – May 2 |
| Laurel | Feb 24 – Mar 10 | Apr 7 – Apr 21 |
| Sidney | Mar 2 – Mar 16 | Apr 13 – Apr 27 |
| Lockwood | Mar 1 – Mar 15 | Apr 12 – Apr 26 |
| Lewistown | Mar 5 – Mar 19 | Apr 16 – Apr 30 |
Showing the 20 most populous of 20 Montana cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Montana cities.
Frequently Asked Questions
When should I plant onions in Montana?
In a typical Montana location, start seeds indoors Mar 5 – Mar 19, then transplant outdoors Apr 16 – Apr 30. Across the state, the outdoor planting window starts as early as Apr 7 in Laurel and as late as May 16 in Butte.
When is the last frost in Montana?
The average last spring frost in Montana ranges from May 5 in Laurel to June 13 in Butte, 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 Montana
- Tomatoes
- Peppers
- Eggplant
- Cucumbers
- Zucchini
- Winter Squash
- Pumpkins
- Watermelon
- Cantaloupe
- Corn
- Green Beans
- Peas
- Lettuce
- Spinach
- Kale
- Arugula
- Swiss Chard
- Broccoli
- Cauliflower
- Cabbage
- Brussels Sprouts
- Carrots
- Beets
- Radishes
- Turnips
- Garlic
- Potatoes
- Sweet Potatoes
- Asparagus
- Basil
- Cilantro
- Parsley
- Dill
- Oregano
- Thyme
- Sunflowers
- Zinnias
- Marigolds
- Cosmos
- Nasturtiums
- Dahlias
When to plant onions in other states