Plant Hardiness Zones 2023

The Plant Hardiness Zone Map (PHZM) is based on the average annual extreme minimum winter temperature, displayed as 10-degree F zones ranging from zone 1 (coldest) to zone 13 (warmest). Each zone is divided into half zones designated as ‘a’ and ‘b’. For example, 7a and 7b are 5-degree F increments representing the colder and warmer halves of zone 7, respectively. These designations serve as convenient labels and shorthand for communicating and comparing the extreme winter temperatures within the United States and Puerto Rico. Zone numbers are typically listed with the descriptions of perennial plants in catalogs and other sales information produced by commercial nurseries, plant suppliers, etc. The sequence of colors assigned to the zones mimics the chromatic spectrum produced by a prism (i.e., red, orange, yellow, green, blue, indigo, and violet), providing a graphical representation of the plant hardiness zones. The overlay of colored zones on the map provides a convenient tool for understanding and comparing plant cold-hardiness across the United States and can facilitate the selection of appropriate perennial plants based on their observed performance in other regions of the country.植物耐寒区地图（Plant Hardiness Zone Map，PHZM）以年均极端最低冬季气温为基准进行划分，采用以华氏10度为间隔的分区体系，从最冷的1区到最暖的13区不等。每个大区均被细分为以‘a’和‘b’标识的半区。例如，7a与7b以华氏5度为间隔，分别对应7区中较冷和较暖的半段区域。上述分区标识可作为便捷的标签与简称，用于在美国及波多黎各境内交流和对比极端冬季气温状况。在商业苗圃、植物供应商等机构的商品目录及其他销售资料中，分区编号通常会与多年生植物的相关描述一并标注。为各分区配置的色彩序列模仿了棱镜产生的色谱（即红、橙、黄、绿、蓝、靛、紫），以此直观呈现植物耐寒区的分布。将彩色分区叠加于地图之上，可为全美范围内的植物耐寒性对比与认知提供便捷工具，同时也能帮助种植者参照其他区域的植物生长表现，筛选适配的多年生植物。