When to plant onions in Alabama
Alabama’s average last spring frost is March 25, and the first fall frost typically arrives around November 5 — about 225 frost-free days (USDA zones 7b, 8a, 8b, 9a). Onion needs 90–120 days to mature, which fits comfortably within Alabama's growing season.
When to plant onions in Alabama: the short answer
For a spring planting, plant out Feb 25 – Mar 14, with seeds started indoors Jan 7 – Jan 21. Seeds germinate in soil from 40 to 90°F.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow onions in Alabama, step by step
- Start seeds indoors (Jan 7 – Jan 21). Sow seeds ½ inch deep in seed-starting mix under bright light. They take 7-14 days to sprout, fastest in soil around 70°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 12 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Plant out (Feb 25 – Mar 14). Space plants about 4 inches apart in rows 12 inches apart. It handles frost well, so it can go out before the last frost date. As a cool-season crop it does best before summer heat arrives in Alabama.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: onion maggot, onion thrips. Diseases and disorders: downy mildew, white rot, neck rot, purple blotch.
- Harvest (from about Jun 2 – Jul 2). Onion takes 90-120 days to reach harvest. Match the day-length type to your latitude: long-day onions for the north, short-day for the south, day-neutral anywhere. Bulbing is triggered by day length, not calendar date.
Figures come from our crop data; dates use Alabama’s average frost dates. More in the full onion growing guide.
Onion planting dates by USDA zone in Alabama
Alabama spans USDA zones 7b, 8a, 8b, 9a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the onion dates shift with them.
When to plant onions in nearby states
| State | Last frost | Plant out |
|---|---|---|
| Alabama (this page) | March 25 | Feb 25 – Mar 14 |
| Mississippi | March 20 | Feb 20 – Mar 9 |
| Louisiana | March 5 | Feb 5 – Feb 22 |
| Florida | February 12 | Jan 15 – Feb 1 |
| Arkansas | April 3 | Mar 6 – Mar 23 |
Questions gardeners in Alabama ask
When is the best time to plant onions in Alabama?
Plant onion transplants outdoors in Alabama between February 25 and March 14. That timing is set by Alabama's average last spring frost of March 25.
When should I start onion seeds indoors in Alabama?
Start seeds indoors between January 7 and January 21, about 10 weeks before the last frost, so the seedlings are ready to plant out from February 25.
When will onions planted in Alabama be ready to harvest?
Planted on time, onions are usually ready from about June 2 to July 2, 90-120 days after transplanting.
When is the last frost in Alabama?
On average around March 25, with the first fall frost around November 5 - about 225 frost-free days. Your town may differ by two weeks or more.