Alabama planting calendar

When to plant onions in Alabama — sow, transplant & harvest dates

Alabama is mostly USDA zone 8a (range 7a-9a). Dates below are derived from onions's frost tolerance and Alabama's frost window — not generic national averages.

Onions planting timetable for Alabama

Stage	When in Alabama	Anchor
Start seeds indoors	mid-January (January 14)	10 weeks before the last frost (late March)
Transplant outside	late February (February 25)	28 days before the last frost (late March)
First harvest (estimate)	mid-June (June 15)	~110 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Alabama's climate shifts the onions dates

Alabama's last spring frost averages late March and first fall frost early November, which sets the whole planting clock. Alabama has a long, hot, humid growing season with mild winters. Heat and humidity, not cold, are the main limits for most of the state. Sow early — onions bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Onions are day-length sensitive: long-day varieties (zones 1–6) begin bulbing when days exceed 14 hours, short-day types (zones 7–10) bulb at 10–12 hours, and intermediate-day varieties span zones 5–6. Start seeds indoors 10–12 weeks before the last spring frost and transplant out 4–6 weeks before it — young onion seedlings tolerate frost down to about -6 °C once hardened off. In zones 8–10 a second planting from sets in autumn is common, overwintering for an early-summer harvest.

Frost-risk note

Don't plant before late March — a hard freeze can still set young plants back. In the northern Appalachian foothills (zone 7a) the safe date runs a week or two later.

Regional variation within Alabama

the northern Appalachian foothills (zone 7a) runs roughly 1-2 weeks behind the state average; the Gulf Coast around Mobile (zone 9a) can plant 1-2 weeks earlier.

Birmingham — USDA zone 8a
Montgomery — USDA zone 8b
Mobile — USDA zone 9a
Huntsville — USDA zone 7b
Tuscaloosa — USDA zone 8a

What else to plant in Alabama around then

The same early window suits peas, lettuce, spinach, and onion sets.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 10-35 °C (50-95 °F).
Spacing: 4-6 inches (10-15 cm) between plants.
Days to harvest: ~110 days from planting out.

Frequently asked questions

When is the best time to plant onions in Alabama?

In Alabama (mostly USDA zone 8a), sow onions indoors around mid-January, transplant outdoors late February (before the last frost, late March), and harvest from mid-June. Onions are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

What USDA zone is Alabama?

Most of Alabama sits in USDA hardiness zone 8a, with the state spanning roughly 7a-9a from the northern Appalachian foothills (zone 7a) to the Gulf Coast around Mobile (zone 9a). The last spring frost averages late March and the first fall frost early November.

Can you grow onions in Alabama?

Yes. Alabama's dominant zone 8a supports onions — the key is timing. Onions are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

Does the planting date change across Alabama?

the northern Appalachian foothills (zone 7a) runs roughly 1-2 weeks behind the state average; the Gulf Coast around Mobile (zone 9a) can plant 1-2 weeks earlier.

What else can I plant in Alabama around the same time?

The same early window suits peas, lettuce, spinach, and onion sets.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.