When to Plant Sunflower in Idaho

Growing Sunflower in Idaho: Complete Guide

Sunflower (Helianthus annuus) is a crop that grows best when sown directly in the garden. In Idaho, the right time to direct sow is around Wednesday, April 22, 2026, once soil temperatures are consistently warm enough for germination.

Because Idaho stretches across 8 USDA hardiness zones (4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b), 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 80 days to maturity, Sunflower fits comfortably within Idaho's growing season in most zones. In the warmest parts of the state, a second planting later in the season may be possible.

Sunflower requires full sun (6-8 hours) and low-moderate (1 inch/week) moisture. Mountain-state gardens contend with short seasons and intense UV at elevation — cold nights can persist well into June at higher altitudes.

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 Idaho.