When to Plant Onion in Hawaii

Growing Onion in Hawaii: Complete Guide

Onion (Allium cepa) is a warm-season crop that needs a head start indoors before Hawaii's last frost. Most Hawaii gardeners begin seeds indoors around Friday, November 6, 2026 and move transplants outside around Friday, January 15, 2027, after the risk of frost has passed.

Because Hawaii stretches across 6 USDA hardiness zones (10b, 11a, 11b, 12a, 12b, 13a), planting windows can shift by as much as six to eight weeks from one end of the state to the other. Gardeners in the warmer southern zones can start earlier, while those in cooler northern zones should wait until the zone table above shows their last frost has passed.

With 100 days to maturity, Onion needs the indoor head start that Hawaii's growing season requires. Starting indoors ensures you have strong transplants ready the moment outdoor conditions are right.

Onion requires full sun (6+ hours) and moderate moisture. Hawaii's year-round warmth allows continuous planting, though elevation and trade wind exposure create distinct growing pockets.

For the most precise planting dates tailored to your exact location, enter your ZIP code on our planting calendar or use the zone table above to find the schedule for your area of Hawaii.