When to plant brussels sprouts in USDA Zone 4b

Plan your brussels sprouts 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: challenging
Brussels sprouts needs a long season and this zone averages just 130 frost-free days. Start early, use black plastic, and plan for row cover on shoulder-season frosts.

Key dates

Start seeds indoors
March 27 – April 10
Transplant outdoors
April 24 – May 15
Expected first harvest
August 9 – September 6
Fall planting window
May 12 – June 2
Fall harvest window
August 27 – September 24

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
24″
Row spacing
36″
Seed depth
0.25″
Soil temperature
55–75°F
Frost tolerance
hardy
Days to harvest
100 days

Grower notes for Zone 4b

Fall-only crop in the Southeast. Top the plant 4 weeks before target harvest for uniform sprouts up the stem.

Plant near: onions, dill

Keep away from: strawberries

Other brassicas 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.