Planting Zones in the United States

U.S. gardeners have planting zones to use as guides for choosing vegetables, trees, flowers and grass. The zones represent specific parts of the United States and their average minimum temperatures. Plants or seeds you purchase at a nursery will have a U.S. Department of Agriculture hardiness rating, which identifies the particular zone or zones where they will grow best.

Zone 1 has an average minimum temperature of below -50 degrees Fahrenheit. Cities in Zone 1 include Resolute Northwest Territories in Canada and Fairbanks, Alaska. Zone 2 has two zones, 2a and 2b. Zone 2a has an average minimum temperature of between -50 and -45 degrees Fahrenheit. Cities in Zone 2a include Flin Flon, Manitoba, Canada and Prudhoe Bay, Alaska. Zone 2b has a minimum temperature of between -45 and -40 degrees Fahrenheit. Cities in Zone 2b include Pinecreek, Minnesota and Unalakleet, Alaska.

Zone 3 also has two zones. Zone 3a has a minimum temperature of between -40 and -35 degrees Fahrenheit. Cities included in the hardiness zone include St. Michael, Alaska and International Falls, Minnesota. Zone 3b includes the cities of Sidney, Montana and Tomahawk, Wisconsin. The minimum temperature in this zone is between -35 and -30 degrees Fahrenheit. The two Zone 4 zones are Zone 4a, which includes the cities Lewistown, Montana and Minneapolis/St. Paul; and Zone 4b, which includes Nebraska and Northwood, Iowa. The average minimum temperature in Zone 4a is between -30 and -25 degrees Fahrenheit. Zone 4b temperatures are between -25 and -20 degrees Fahrenheit.

Des Moines, Iowa and Illinois are in Zone 5a, which has a average temperature of between -20 and -15 degrees Fahrenheit. Mansfield, Pennsylvania and Columbia, Missouri are in Zone 5b, which has an average low temperature of between -15 and -10 degrees Fahrenheit. Lebanon, Pennsylvania and St. Louis, Missouri are cities in Zone 6a, which has a minimum average temperature of between -10 and -5 degrees Fahrenheit. Branson and McMinnville, Tennessee are in Zone 6b, which has a low temperature minimum of between -5 and 0 degrees Fahrenheit.

Zone 7 and Zone 8 have two zones. Zone 7a has an average temperature of between 0 and 5 degrees Fahrenheit, while Zone 7b has an average temperature of between 5 and 10 degrees Fahrenheit. Cities in Zone 7a include South Boston, Virginia and Oklahoma City. Zone 7b cities include Griffin, Georgia and Little Rock, Arkansas. Zone 8a includes the cities of Dallas and Tifton, Georgia. Average minimum temperatures are between 10 and 15 degrees Fahrenheit in Zone 8a and Zone 8b temperatures are between 15 and 20 degrees Fahrenheit. Zone 8b cities include Gainesville, Florida and Austin, Texas.

Zone 9a minimum average temperatures are between 20 and 25 degrees Fahrenheit, which include the cities of St. Augustine, Florida and Houston. Zone 9b includes the cities of Fort Pierce, Florida and Brownsville, Texas. The average minimum temperature is between 25 and 30 degrees Fahrenheit. Zone 10a includes Victoria, California and Naples, Florida. The minimum temperature is between 30 and 35 degrees Fahrenheit. Coral Gables and Miami, Florida are included in Zone 10b, which has a minimum average temperature of between 35 and 40 degrees Fahrenheit.

Zone 11 has an average temperature of above 40 degrees Fahrenheit. Honolulu, Hawaii is included in Zone 11.