When to plant lettuce in USDA Zone 4a

Plan your lettuce 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.

Fargo ND, northern MN, northern WI, northern ME. Average last spring frost May 22, first fall frost September 15 — a 116-day frost-free season.

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

Key dates

Start seeds indoors
April 17 – May 1
Direct-seed or transplant outdoors
April 17 – May 8
Expected first harvest
June 8 – July 6
Fall planting window
July 14 – August 4
Fall harvest window
September 4 – October 2

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
8″
Row spacing
12″
Seed depth
0.125″
Soil temperature
45–70°F
Frost tolerance
half-hardy
Days to harvest
45 days

Grower notes for Zone 4a

Successive plantings every 10–14 days for continuous harvest. Bolts fast above 75°F — use heat-tolerant varieties past May.

Plant near: carrots, radish, strawberries

Other leafy greens for Zone 4a

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.