When to Plant Onion in Montrose, California (91021)

Location

Montrose, California

ZIP Code

91021

USDA Zone

10a

Last Frost

Sunday, January 25, 2026

📅 Planting Calendar

Start Seeds Indoors Sunday, November 30, 2025

Transplant Outdoors Sunday, February 8, 2026

Pro Tip: Start Onion seeds indoors 8 weeks before your last frost date, then transplant outdoors around Sunday, February 8, 2026.

🌿 Plant Details

Scientific Name Allium cepa

Days to Maturity 100 days

Mature Height 12-18"

Spread 4"

Type Bulb

Fruit Size Medium (2-4 inch bulb)

☀️ Growing Requirements

☀️

Sun

Full Sun (6+ hours)

💧

Water

Moderate

↔️

Spacing

4" apart

🌱

Planting Depth

0.5" deep

Seeds typically germinate in 7-10 days

Ready to Plant Onion in Montrose?

Get your seeds now so they're ready by Sunday, November 30, 2025.

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🤝 Good Companions

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⚠️ Avoid Planting Near

BeanPeaAsparagus

Other Plants for Montrose

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Growing Onion in Zone 10a

Onion (Allium cepa) is a popular garden vegetable. In Montrose, California, which is in USDA Hardiness Zone 10a, you should start seeds indoors around Sunday, November 30, 2025.

Your average last frost date is Sunday, January 25, 2026. Plan to transplant your Onion seedlings outdoors around Sunday, February 8, 2026, about 2 weeks after your last frost date.