Plant Hardiness Zone: Zone 1

Average annual extreme minimum temperature below -50°F (-45.6°C)

This is the coldest zone, found in the most extreme northern regions of the United States (like parts of Alaska) and Canada. Gardening here is challenging, requiring plants that are exceptionally cold-hardy, often native arctic or subarctic species. Many plants that thrive in warmer zones will need significant winter protection or must be grown as annuals.