Plant hardiness zone
A plant hardiness zone is a geographical area defined by the ability of plants to survive the winter in that zone. The United States Department of Agriculture defines plant hardiness zones by average annual extreme minimum temperature and revises these zones periodically, most recently in 2012, to account for temperature changes. A gardener can use the zones to tell which plants will survive the winter in his area. For example, if a plant is listed as hardy from zones 3-8, a gardener in a zone below 3 or above 8 will know that the plant will survive with difficulty, if at all.