Plants vary in their ability to survive the winter. Plants that thrive in the warmth of a tropical Florida will grow less well in cooler areas and will be killed in winter in Alaska. The trick is to know which are which - and this is where the US hardiness zones come in.
The USDA has split the country into 13 zones according to the average lowest winter temperature recorded at weather stations across the country in the ten years up to 2020. (The two very warmest zones cover very small areas and are usually omitted.) At the same time, the nation’s expert professional and home gardeners, and particularly the American Horticultural Society, have used their expertise to assign all the plants we grow in the United States and Canada (and farther afield) with a corresponding rating that instantly indicates the lowest winter temperature they will survive.
