When to plant winter squash in USDA Zone 3b

Plan your winter squash planting around local frost risk and soil temperature, then work backward from the harvest week your buyers need. The calendar below is a starting point, not a field-level weather forecast.

Grand Forks & Minot ND, northern MN border counties. Average last spring frost May 25, first fall frost September 10 — a 108-day frost-free season.

Zone fit: challenging
Winter squash needs a long season and this zone averages just 108 frost-free days. Start early, use black plastic, and plan for row cover on shoulder-season frosts.

Key dates

Direct-seed outdoors
June 1 – June 22
Expected first harvest
September 16 – October 14

Windows are calculated from your zone's average frost dates. Adjust ±1 week for microclimates, elevation, and your own frost records.

Spacing and soil

Plant spacing
36″
Row spacing
72″
Seed depth
1″
Soil temperature
70–90°F
Frost tolerance
tender
Days to harvest
100 days

Grower notes for Zone 3b

Cure fruit at 80–85°F for 10 days after harvest to extend storage. Plant early enough to mature before first frost.

Plant near: corn, beans

Keep away from: potatoes

Other cucurbits for Zone 3b

Same crop, other zones

Track your own plantings

BAU Farm Intelligence turns these windows into per-field tasks — indoor seed-start reminders, transplant dates, harvest projections — using your farm's actual frost history.