When to plant Lettuce in Montana

In spring, from Apr 1 – June 1 in Billings to May 20 – June 30 in Butte-Silver Bow (balance).

In fall, from May 15 – July 15 in Butte-Silver Bow (balance) to July 15 – Sept 1 in Billings.

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

Leaf lettuce planting dates by place in Montana
PlaceSpringFall
BelgradeMay 10 – June 30June 1 – Aug 1
BillingsApr 1 – June 1July 15 – Sept 1
BozemanMay 10 – June 30June 1 – Aug 1
Butte-Silver Bow (balance)May 20 – June 30May 15 – July 15
Great FallsApr 15 – June 15June 1 – Aug 1
HelenaApr 15 – June 15June 1 – Aug 1
KalispellMay 10 – June 30May 15 – July 15
MissoulaApr 15 – June 15June 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 leaf lettuce.