When it comes to gardening, one of the critical factors for success is to consider your climate. Different plants have different temperature and weather preferences, and what will thrive in one region will struggle or die in another. To help gardeners understand the unique characteristics of their local climate, the United States Department of Agriculture (USDA) has developed a system of gardening zones to differentiate the growing seasons in various regions across the country. This system partitions the country into zones based on each region’s unique set of weather and soil conditions that impact gardening.
The USDA gardening zone map was created in 1960 and updated in 2021. The map divides the United States into 13 zones, ranging from Zone 1 (the coldest) to Zone 13 (the warmest). Each zone is defined by the average minimum temperature in that region, then broken into subzones based on geographical features such as altitude and proximity to bodies of water and planting zone maps.
Here is a breakdown of the gardening zones in the US:
Zone 1: Covers the very coldest areas of the country, with average minimum temperatures ranging from -60°F to -50°F, confined to areas of Alaska.
Zone 2: Comprised of areas with average minimum temperatures ranging from -50°F to -40°F, parts of southern Alaska, northernmost parts of Montana, North Dakota, and Minnesota.
Zone 3: This zone sweeps across the very northern rim of the contiguous US, northern Montana, North Dakota, Minnesota, New York, Vermont, New Hampshire and Maine, where gardening zones have an average minimum temperatures range from -40°F to -30°F.
Zone 4: This zone consists of areas with average minimum temperatures ranging from -30°F to -20°F, made up of parts of Idaho, Wyoming, Colorado, Montana, South Dakota, Minnesota, Wisconsin and Michigan, along with South Dakota, Wisconsin, parts of Vermont, New Hampshire and Maine.
Zone 5: Average minimum temperatures in this zone range from -20°F to -10°F, reaching across the Central United States, including eastern Colorado, Nebraska, Indiana, Illinois, Indiana, Ohio, Pennsylvania, and up into the New England states.
Zone 6: The planting zone map covers areas with average minimum temperatures ranging from -10°F to 0°F, states including Washington, Oregon, Nevada, Utah, down into northern Arizona and New Mexico, Kansas, Missouri, southern Illinois, Indiana, Ohio, Kentucky, West Virginia, Pennsylvania, New Jersey, Connecticut, Massachusetts and Rhode Island.
Zone 7 covers areas with average minimum temperatures ranging from 0°F to 10°F. This includes parts of Arizona, New Mexico, Texas, Oklahoma, Arkansas, northern Mississippi and Georgia, Tennessee, North Carolina, Virginia and Maryland.
Zone 8: Made up of states with average minimum temperatures ranging from 10°F to 20°F. These include western Washington and Oregon, along with Texas, Louisiana, southern Arkansas, Texas, Louisiana, Mississippi, Alabama, Georgia, South Carolina and northern Florida.
Zone 9 covers areas with average minimum temperatures ranging from 20°F to 30°F. This includes parts of Arizona, New Mexico, Texas, Oklahoma, Arkansas, northern Mississippi and Georgia, Tennessee, North Carolina, Virginia and Maryland.
Zone 10: The gardening zone comprises of areas with rare frost or freezing temperatures, averaging from 30°F to 40°F minimum. This includes parts of California, Arizona, New Mexico, Texas and Florida.
Zone 11: This zone covers areas with average minimum temperatures ranging from 40°F to 50°F. This includes parts of Hawaii.
Zone 12: Tropical regions where the average minimum temperatures range from 50°-60° Fahrenheit, covering Hawaii, Puerto Rico, and the US Virgin Islands.
Zone 13: The smallest zone with average minimum temperatures above 60 degrees. It only covers the Florida Keys.
The USDA planting zone map is an essential tool for American gardeners. By understanding the unique characteristics of their local climate, gardeners can create a thriving garden. In addition to choosing plants based on their gardening zone, gardeners must also consider soil type, sun exposure, and moisture levels.