Montana · zones 4a–5b
When to plant potatoes in Montana.
Sow between Apr 7 to May 10 in a typical year, keyed to Montana's median last frost around May 15. A second, fall sowing fits Jun 5 to Jun 18. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Potatoes dates for a typical Montana season.
Direct sow
Apr 7 to May 10
Keyed to the ~May 15 last frost. Sow 4" deep, 12" apart.
Fall round
Jun 5 to Jun 18
Counted back from the ~Sep 23 first frost.
Harvest
~90 days later
~3 lb per plant over ~1 weeks.
Montana spans more than one climate: Zone 4 is the most common zone, but the state runs 4a to 5b. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In Montana: watch for
The pests that find potatoes here.
The short season here, about 131 frost-free days, keeps potato in front of colorado potato beetle only briefly. One early row cover usually carries a planting through the worst of it.
Striped beetles and orange grubs eating the leaves.
Organic fix: Handpick adults, crush the orange egg clusters, dust with diatomaceous earth.
Dark greasy blotches after cool, wet spells.
Organic fix: Pull infected plants fast, keep leaves dry, use neem as a preventive.
Common scab
Rough, corky patches on the skin, raised on some tubers and sunk into pits on others.
Organic fix: Keep the bed evenly moist through the weeks right after tubers set, rotate away from potatoes, and pick a scab-resistant variety next time.
Your season math: Montana gives potatoes about 131 frost-free days, and it needs roughly 90 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting potatoes in Montana: questions
When should I plant potatoes in Montana?+
In a typical Montana year, sow potatoes between Apr 7 to May 10, keyed to the state's median last frost around May 15. There's also a fall window: Jun 5 to Jun 18. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Montana?+
Montana spans zones 4a–5b, mostly zone 4. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many potatoes plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.