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🧅 Growing Onion in Zone 12a

Zone 12a has a year-round growing season. Onion can be planted almost any time with proper planning. Last frost: Jan 1. First frost: Dec 31.

Planting Calendar

Indoor

Outdoor

Harvest

Oct 23Dec 31

Season: Jan 1 – Dec 31 (364 days)

Zone12a

Last FrostJan 1

First FrostDec 31

Season Length364 days

Days to Harvest110

SunFull Sun

Frost ToleranceModerate

Spacing9/sqft (4" apart)

When to Plant Onion in Zone 12a

Start Seeds Indoors: Oct 23

Start Onion seeds indoors around Oct 23 (10 weeks before last frost). Optimal germination temperature: 70°F. Germinates in 7–14 days.

Transplant Outdoors: Dec 4

Transplant Onion seedlings outdoors after Dec 4. Wait until soil temperature reaches 45°F. Space plants at 9/sqft (4" apart). Harden off plants for a week before moving outside.

Harvest: Feb 22

First harvest approximately Feb 22 (~80 days from transplant). Continue harvesting until first frost (Dec 31).

Companion Planting

✅ Strawberries✅ Cabbage✅ Beets✅ Lettuce✅ Carrots✅ Tomatoes

❌ Beans❌ Peas

Onion in Other Zones

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13b

Frequently Asked Questions

When should I plant Onion in Zone 12a?

Start Onion seeds indoors around Oct 23. Transplant outdoors after Dec 4. Expect first harvest around Feb 22.

What is the last frost date for Zone 12a?

The average last spring frost date for Zone 12a is Jan 1. The first fall frost averages Dec 31, giving a 364-day growing season.

Can I grow Onion in Zone 12a?

Yes. Onion needs 110 days to harvest. Zone 12a has a 364-day growing season, which is sufficient.

What is the best month to plant Onion in Zone 12a?

The best time to start Onion in Zone 12a is Oct. Begin seeds indoors around Oct 23, then transplant outdoors after the last frost date of Jan 1.

What companion plants grow well with Onion?

Good companion plants for Onion include Strawberries, Cabbage, Beets, Lettuce, Carrots, Tomatoes. Avoid planting Onion near Beans, Peas.

How long does Onion take to harvest?

Onion takes approximately 110 days from planting to harvest. In Zone 12a, expect your first harvest around Feb 22.

Plan Your Onion Garden

Track Onion from seed to harvest with personalized frost dates, watering recommendations, and companion planting visualization.

Start Free Onion Growing Guide