When to Plant Onion in Colorado Springs, Colorado (80921)

Location

Colorado Springs, Colorado

ZIP Code

80921

USDA Zone

Last Frost

Saturday, April 25, 2026

📅 Planting Calendar

Start Seeds Indoors Saturday, February 28, 2026

Transplant Outdoors Saturday, May 9, 2026

Pro Tip: Start Onion seeds indoors 8 weeks before your last frost date, then transplant outdoors around Saturday, May 9, 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 Colorado Springs?

Get your seeds now so they're ready by Saturday, February 28, 2026.

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🤝 Good Companions

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⚠️ Avoid Planting Near

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Growing Onion in Zone 5b

Onion (Allium cepa) is a popular garden vegetable. In Colorado Springs, Colorado, which is in USDA Hardiness Zone 5b, you should start seeds indoors around Saturday, February 28, 2026.

Your average last frost date is Saturday, April 25, 2026. Plan to transplant your Onion seedlings outdoors around Saturday, May 9, 2026, about 2 weeks after your last frost date.