When to plant rosemary in Montana
Montana spans USDA zones 4b–5b, so the right time to plant rosemary shifts by weeks across the state. The window to transplant seedlings outdoors runs from about May 11 in Billings to June 20 in Butte-Silver Bow — below are local dates for 8 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Billings | 5a | May 4 | October 7 | May 11 – May 18 |
| Missoula | 5b | May 10 | October 1 | May 17 – May 24 |
| Great Falls | 4b | May 6 | October 1 | May 13 – May 20 |
| Bozeman | 5a | May 26 | September 22 | June 2 – June 9 |
| Butte-Silver Bow | 5a | June 13 | September 5 | June 20 – June 27 |
| Helena | 5a | May 9 | September 30 | May 16 – May 23 |
| Kalispell | 5b | May 31 | September 10 | June 7 – June 14 |
| Belgrade | 5a | May 26 | September 16 | June 2 – June 9 |
Rosemary in Montana: FAQ
When can I plant rosemary in Montana?
Across Montana, the time to transplant rosemary spans roughly May 11 in Billings to June 20 in Butte-Silver Bow, each following that city's local frost dates.
Does the rosemary planting date vary across Montana?
Yes. Montana publishes 8 cities with their own frost dates, so the right rosemary planting window shifts by weeks between the warmest and coldest parts of the state — use your city's page for the exact dates.
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