The USDA (United States Department of Agriculture) has divided the United States into 13 different plant hardiness zones based on the average annual minimum winter temperature. These zones are helpful in determining which plants are likely to thrive in a particular area.
Idaho falls into USDA plant hardiness zones 3 through 7, with the northern part of the state in zones 3 and 4, and the southern part of the state in zones 5 through 7. The higher the number, the milder the winter temperatures, and the greater variety of plants can be grown. Here is a breakdown of the plant hardiness zones in Idaho:
- Zone 3: The coldest part of Idaho, with minimum average winter temperatures ranging from -40 to -30 degrees Fahrenheit (-40 to -34 degrees Celsius). This zone covers the northern part of the state, including towns such as Coeur d’Alene and Sandpoint.
- Zone 4: This zone covers a large portion of Idaho, including cities such as Moscow, Lewiston, and Boise. Minimum average winter temperatures range from -30 to -20 degrees Fahrenheit (-34 to -29 degrees Celsius).
- Zone 5: This zone covers a smaller part of southern Idaho, including cities such as Twin Falls, Pocatello, and Idaho Falls. Minimum average winter temperatures range from -20 to -10 degrees Fahrenheit (-29 to -23 degrees Celsius).
- Zone 6: This zone covers an even smaller part of southern Idaho, including cities such as Jerome and Burley. Minimum average winter temperatures range from -10 to 0 degrees Fahrenheit (-23 to -18 degrees Celsius).
- Zone 7: The mildest part of Idaho, with minimum average winter temperatures ranging from 0 to 10 degrees Fahrenheit (-18 to -12 degrees Celsius). This zone covers a small area in the southwestern corner of the state, including cities such as Boise and Nampa.
It’s important to note that while these zones provide a general guide to plant hardiness, other factors such as soil type, humidity, and wind can also impact a plant’s ability to grow in a particular location.