When to plant spinach in USDA Zone 4b

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.

Minneapolis, Duluth, central WI, northern VT/NH. Average last spring frost May 15, first fall frost September 22 — a 130-day frost-free season.

Zone fit: excellent
Spinach is well suited to Zone 4b. Standard planting dates work with minor adjustments for microclimates.

Key dates

Direct-seed outdoors
March 27 – April 17
Expected first harvest
May 18 – June 15
Fall planting window
July 21 – August 11
Fall harvest window
September 11 – October 9

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 4b

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 4b

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.