When to plant Turnips in Montana

In spring, from Mar 20 – May 1 in Billings to May 15 – June 15 in Butte-Silver Bow (balance).

In fall, from June 1 – July 15 in Belgrade to July 1 – Aug 1 in Billings.

USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.

Turnips planting dates by place in Montana
PlaceSpringFall
BelgradeMay 1 – June 15June 1 – July 15
BillingsMar 20 – May 1July 1 – Aug 1
BozemanMay 1 – June 15June 1 – July 15
Butte-Silver Bow (balance)May 15 – June 15June 1 – July 1
Great FallsApr 1 – June 1June 1 – Aug 1
HelenaApr 1 – June 1June 1 – Aug 1
KalispellMay 1 – June 15June 1 – July 1
MissoulaApr 1 – June 1June 1 – Aug 1

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 turnips.