Plant hardiness is a term that refers to the ability of plants to survive adverse climatic conditions, especially cold temperatures. Different plants have different levels of hardiness, depending on their native geographic location and adaptation. The USDA Plant Hardiness Zone Map is a tool that helps gardeners and growers to determine which plants are most likely to thrive in their location, based on the average annual minimum winter temperature. The map divides the country into 10-degree F zones and 5-degree F half-zones, ranging from zone 1a (below -60 F) to zone 13b (65 to 70 F). By knowing the plant hardiness zone of their area, gardeners can choose plants that are suitable for their climate and avoid planting those that are too tender or too hardy.