When to plant onions (bulbing) in USDA Zone 9b

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.

Orlando, Tampa, San Antonio, southern LA coast. Average last spring frost February 5, first fall frost December 15 — a 313-day frost-free season.

Zone fit: good
Cool-season crops bolt fast under Zone 9b heat. Prioritize the fall planting window and use shade cloth for any spring succession.

Key dates

Start seeds indoors
November 20 – December 4
Transplant outdoors
December 18 – January 8
Expected first harvest
April 4 – May 2

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 9b

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 9b

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.