When to Plant Cosmos in Alaska

Growing Cosmos in Alaska: Complete Guide

Cosmos (Cosmos bipinnatus) is a crop that grows best when sown directly in the garden. In Alaska, the right time to direct sow is around Sunday, May 10, 2026, once soil temperatures are consistently warm enough for germination.

Because Alaska stretches across 16 USDA hardiness zones (1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b), 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 60 days to maturity, Cosmos fits comfortably within Alaska's growing season in most zones. In the warmest parts of the state, a second planting later in the season may be possible.

Cosmos requires full sun (6-8 hours) and low-moderate moisture. Alaska's long summer days accelerate growth, but frost can arrive early in August — season extension with row covers is essential.

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 Alaska.