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Idaho’s Growing Regions

 

Idaho Climate MapDepending on where you live in Idaho, fruits and vegetables often make fine additions to a home garden and landscape. Idaho’s topography and climate are incredibly diverse, from the high desert to lush temperate rain forests to alpine meadows. Success in gardening starts with choosing crops that are well adapted to your site and climate.

With exceptions, Idaho can be divided roughly into four climatic and topographic regions: northern, central, southeastern, and southwestern. Each area has unique soil and climate conditions that affect what plants will grow well there.

Northern through central Idaho is a mountainous, often heavily forested region. Along the western edge of the panhandle lie rolling hills of grasslands and extensive grain fields. Except for the low, warm Clearwater River drainage around Lewiston and Orofino, the growing season is short and relatively cool. At higher elevations and along the eastern side of the state, winter temperatures can fall to -30°F or colder. The frost free growing season is about 90 to 150 days in the valleys and 60 to 90 days in the mountains. Soils in the region are generally slightly to very acid and range from sandy to heavy clay soils. Silt loam soils are common and poor soil drainage is often a concern. For this region, cold hardy, early ripening fruit and cool-season vegetable varieties perform best. In and around Lewiston, the growing season is substantially longer and warmer, making the region suitable for many fruit varieties.

Southeastern Idaho includes high plains and desert to the west, leading to foothills and high mountains to the east. Winters are often cold, with temperatures of -30°F and below not uncommon. Despite high daytime summer temperatures, the overall growing season is short and relatively cool. Throughout most of the region, the frost-free growing season ranges from 30 days at the highest elevations to 150 days in the valleys and plains. Along the Snake River drainages from Idaho Falls west, the growing season can be 150 days or longer. Annual precipitation is 20 inches or less, except in the mountains, where 30 inches of precipitation is typical. Irrigation is required for crop production in most southeastern Idaho sites. Desert and lowland soils are often alkaline and iron chlorosis can be a problem with fruit and vegetable crops on some sites. Mountain soils are generally acidic. Soils range from sand to heavy clay, with light-textured soils predominating. As with northern and central Idaho, gardeners will enjoy their greatest success with cold hardy, early ripening fruit and cool season vegetable varieties.

Southwestern Idaho around Boise and Payette is ideal for growing many fruit and vegetable crops. The winter climate is relatively mild and the growing season long and warm, with frost-free periods of 120 to more than 150 days common. Moving eastward, the climate cools, but the Twin Falls area is still suitable for many fruit and vegetable crops. Portions of Owyhee County are cooler still, with a 60 to 90 day frost-free period. Soils in the southwestern Idaho are often alkaline and irrigation water can also be alkaline. Gardeners must be alert for symptoms of iron chlorosis.

To determine the exact climate zone where you live, use the Idaho map provided by Purdue University.

American Horticultural Society Plant Heat Zone Maps

USDA Plant Hardiness Zone Maps