Montana's USDA plant hardiness growing zones range from 3a to 6b. The state covers a wide range of zones due to its diverse climates and geography, including mountainous regions and plains.
- The coldest areas, mainly along the northern and northeastern Canadian border and some pockets in the southwest, fall into zones 3a and 3b, where average minimum winter temperatures range from -40°F to -30°F.
- Much of Montana is in zones 4a and 4b, covering northern, central, and southeastern parts of the state, with average lows between -30°F and -20°F.
- Zones 5a and 5b cover central, southwestern, and some northwestern areas, with lows from -20°F to -10°F.
- The warmest zones, 6a and 6b, are primarily in the northwest, including parts of Sanders, Mineral, Lake, Flathead, and Lincoln counties, with average lows from -10°F to 0°F
Major cities and their zones include:
- Helena: 4b
- Billings: 5a
- Bozeman: 5a
- Missoula: 5b
- Kalispell: 5b
- Great Falls: 4b
This range means gardeners in Montana should select plants that can tolerate cold winters and shorter growing seasons typical of zones 3 through 6. Knowing your specific zone helps determine which plants will thrive in your area
