When to plant blueberries in USDA Zone 4b

Plan your blueberries 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
Blueberries 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

Transplant outdoors
October 23 – November 13
Expected first harvest
October 29 – November 26
Fall planting window
August 4 – August 25
Fall harvest window
August 10 – September 7

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
60″
Row spacing
120″
Seed depth
6″
Soil temperature
50–80°F
Frost tolerance
hardy
Days to harvest
730 days

Grower notes for Zone 4b

Rabbiteye varieties fit Zones 7–9; southern highbush for Zones 8–10. Soil pH 4.5–5.2 is non-negotiable — amend with elemental sulfur.

Plant near: azaleas, rhododendrons

Other berries 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.