When to Plant Butternut Squash in Boulder, Colorado (80310)

Location

Boulder, Colorado

ZIP Code

80310

USDA Zone

Last Frost

Monday, April 20, 2026

📅 Planting Calendar

Start Seeds Indoors Monday, March 23, 2026

Transplant Outdoors Monday, May 4, 2026

Pro Tip: Start Butternut Squash seeds indoors 4 weeks before your last frost date, then transplant outdoors around Monday, May 4, 2026.

🌿 Plant Details

Scientific Name Cucurbita moschata

Days to Maturity 100 days

Mature Height 12-18"

Spread 72"

Type Vine

Fruit Size Large (2-5 lbs)

☀️ Growing Requirements

☀️

Sun

Full Sun (6-8 hours)

💧

Water

Regular (1 inch/week)

↔️

Spacing

60" apart

🌱

Planting Depth

1" deep

Seeds typically germinate in 5-10 days

Ready to Plant Butternut Squash in Boulder?

Get your seeds now so they're ready by Monday, March 23, 2026.

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🤝 Good Companions

CornBeanMarigoldNasturtium

⚠️ Avoid Planting Near

Potato

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Growing Butternut Squash in Zone 6a

Butternut Squash (Cucurbita moschata) is a popular garden vegetable. In Boulder, Colorado, which is in USDA Hardiness Zone 6a, you should start seeds indoors around Monday, March 23, 2026.

Your average last frost date is Monday, April 20, 2026. Plan to transplant your Butternut Squash seedlings outdoors around Monday, May 4, 2026, about 2 weeks after your last frost date.