USDA Zone 1B

Average annual minimum temperature: -48°C to -46°C (-55°F to -50°F)

This is one of the coldest USDA hardiness zones, typical of interior Alaska, northern Canada, and high-altitude regions. Winters are severe enough that most ornamental and vegetable gardening happens in a short, intense summer season. Perennials need to be exceptionally cold-hardy, and many popular garden plants can only be grown as annuals or overwintered indoors.