When to plant broccoli in USDA Zone 4b

Plan your broccoli 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
Broccoli is well suited to Zone 4b. Standard planting dates work with minor adjustments for microclimates.

Key dates

Start seeds indoors
March 27 – April 10
Transplant outdoors
April 17 – May 8
Expected first harvest
June 28 – July 26
Fall planting window
June 9 – June 30
Fall harvest window
August 20 – September 17

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
18″
Row spacing
30″
Seed depth
0.25″
Soil temperature
55–75°F
Frost tolerance
hardy
Days to harvest
65 days

Grower notes for Zone 4b

Harvest the central head while buds are still tight; side shoots continue for 4–6 weeks after main cut.

Plant near: onions, beets, chamomile

Keep away from: tomatoes, 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.