When to plant basil in USDA Zone 4b

Plan your basil 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: good
Basil is frost-tender, so timing the outdoor transplant to the last frost matters more here than in warmer zones. Row cover buys 2 weeks of head start.

Key dates

Start seeds indoors
March 27 – April 10
Transplant outdoors
May 22 – June 12
Expected first harvest
July 23 – August 20
Fall planting window
July 7 – July 28
Fall harvest window
September 7 – October 5

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
12″
Row spacing
18″
Seed depth
0.125″
Soil temperature
70–90°F
Frost tolerance
tender
Days to harvest
55 days

Grower notes for Zone 4b

Pinch flowers weekly to keep leaves productive. Fusarium-resistant varieties are essential for repeat plantings in the same beds.

Plant near: tomatoes, peppers

Keep away from: rue

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.