When to plant onions (bulbing) in USDA Zone 8b

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.

Charleston SC, Savannah, Mobile, Austin, Jacksonville. Average last spring frost March 15, first fall frost November 15 — a 245-day frost-free season.

Zone fit: excellent
Onions (bulbing) is well suited to Zone 8b. Standard planting dates work with minor adjustments for microclimates.

Key dates

Start seeds indoors
December 28 – January 11
Transplant outdoors
January 25 – February 15
Expected first harvest
May 12 – June 9

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 8b

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 8b

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.