When to plant radishes in USDA Zone 4b

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

Key dates

Direct-seed outdoors
April 10 – May 1
Expected first harvest
May 15 – June 12
Fall planting window
August 4 – August 25
Fall harvest window
September 8 – October 6

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
1″
Row spacing
12″
Seed depth
0.5″
Soil temperature
45–70°F
Frost tolerance
hardy
Days to harvest
28 days

Grower notes for Zone 4b

Fastest crop in the garden. Interplant with slow germinators like carrots to mark rows.

Plant near: cucumbers, carrots, lettuce

Keep away from: hyssop

Other root crops 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.