When to plant onions (bulbing) in USDA Zone 6b

Plan your onions (bulbing) 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.

Boone NC, northern VA, central KY, southern IN. Average last spring frost April 24, first fall frost October 8 — a 167-day frost-free season.

Zone fit: challenging
Short-day onion varieties bulb best in Zones 7 and warmer; northern growers should choose intermediate-day types instead.

Key dates

Start seeds indoors
February 6 – February 20
Transplant outdoors
March 6 – March 27
Expected first harvest
June 21 – July 19

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
4″
Row spacing
12″
Seed depth
0.25″
Soil temperature
50–75°F
Frost tolerance
hardy
Days to harvest
100 days

Grower notes for Zone 6b

Southeast growers must plant short-day varieties. Long-day types will make tops but never bulb below 36° latitude.

Plant near: carrots, beets, lettuce

Keep away from: beans, peas

Other alliums for Zone 6b

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.