When to Plant Onion in Haiku, Hawaii (96708)

Location

Haiku, Hawaii

ZIP Code

96708

USDA Zone

12a

Last Frost

Thursday, January 1, 2026

📅 Planting Calendar

Start Seeds Indoors Thursday, November 6, 2025

Transplant Outdoors Thursday, January 15, 2026

Pro Tip: Start Onion seeds indoors 8 weeks before your last frost date, then transplant outdoors around Thursday, January 15, 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 Haiku?

Get your seeds now so they're ready by Thursday, November 6, 2025.

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🤝 Good Companions

CarrotBeetLettuceTomatoBrassicas

⚠️ Avoid Planting Near

BeanPeaAsparagus

Other Plants for Haiku

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Growing Onion in Zone 12a

Onion (Allium cepa) is a popular garden vegetable. In Haiku, Hawaii, which is in USDA Hardiness Zone 12a, you should start seeds indoors around Thursday, November 6, 2025.

Your average last frost date is Thursday, January 1, 2026. Plan to transplant your Onion seedlings outdoors around Thursday, January 15, 2026, about 2 weeks after your last frost date.