Climate Zone Info

What Is Plant Hardiness?

At its most fundamental level, hardiness describes a plant's ability to endure harsh winter temperatures. Drawing upon several decades of climate data, the U.S. Department of Agriculture created the Plant Hardiness Zone Map, which breaks geographical regions into 13 climate zones (with a and b sub-zones) based on a 10-degree Fahrenheit difference in the average annual minimum temperature.

For example, a gardener in zone 5 can be reasonably sure that any plant labeled as hardy for zone 5 or colder will withstand the winter. However, the Hardiness Zone Map doesn't include fluctuations due to altitude, soil, moisture, humidity, heat, or wind, which can dramatically affect a plant's ability to survive.

Knowing your specific gardening zone is the first step in determining what plants will flourish in your gardens and that will live through the winter. So, first identify which USDA Hardiness Zone you are located in. Check out the map below and discover which seeds, bulbs, and plants work best for your region. Oh, and don't worry—there are hardy perennials and annuals eager to enhance even the coldest, most rugged terrain.