When to plant spinach in USDA Zone 3b

Plan your spinach 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: excellent
Spinach is well suited to Zone 3b. Standard planting dates work with minor adjustments for microclimates.

Key dates

Direct-seed outdoors
April 6 – April 27
Expected first harvest
May 28 – June 25
Fall planting window
July 9 – July 30
Fall harvest window
August 30 – September 27

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
4″
Row spacing
12″
Seed depth
0.5″
Soil temperature
40–70°F
Frost tolerance
hardy
Days to harvest
45 days

Grower notes for Zone 3b

Germination stalls above 75°F. Direct-seed while soil is still cool for both spring and fall crops.

Plant near: strawberries, radish

Other leafy greens 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.