When to plant garlic in USDA Zone 4b

Plan your garlic 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
Garlic 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

Direct-seed outdoors
July 31 – August 21
Expected first harvest
April 4 – May 2
Fall planting window
August 18 – September 8
Fall harvest window
April 22 – May 20

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
6″
Row spacing
12″
Seed depth
2″
Soil temperature
45–60°F
Frost tolerance
hardy
Days to harvest
240 days

Grower notes for Zone 4b

Fall-planted only. Plant 4–6 weeks before first frost so roots establish before soil freezes. Harvest when lower 3 leaves brown.

Plant near: tomatoes, brassicas

Keep away from: beans, peas

Other alliums 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.