For Montana lawns, plant cool-season grasses between the last week of July and mid-September, 45 days before the expected first frost. Plant warm-season grass in May or June, when temperatures reach 65 degrees.
Most Montana lawns have cool-season grass, but the ideal planting time varies by location and hardiness zone. Homeowners in northeast Montana can plant as early as late July, while those in the northwest can plant as late as mid-September. Only northwestern Montana lawns are suitable for warm-season grasses, which are best planted in May.
When to plant cool-season grass
In general, the best time to plant cool-season grass in Montana is between the last week of July and mid-September. Planting during this time allows the grass to take root before winter and then become an established lawn during spring, before the summer heat strikes.
However, you can narrow the time frame even further if you know what USDA Growing Zone you live in.
Growing Zone 3
- Location: Along the north-central and northeastern Canadian border and in small pockets in the southwest near the southern Idaho border.
- Average first frost: September 8 to 15
- Best time to plant: July 25 to August 1
Zone 4
- Location: Covers much of the state. Zone 4a borders northern zone 3 and goes as far west as Glacier County. It covers much of the northeastern part of the state, too. Zone 4b includes southeast and central Montana and goes as far west as Pondera and Tetor counties. It also includes pockets in southwestern Montana.
- Average first frost: September 21 to October 7
- Best time to plant: August 7 to August 23
Zone 5
- Location: Covers the central border and most of the southwest. Zone 5 also includes a strip in the northwest between Zone 4 and Zone 6 as well as a few pockets in central and southeastern parts of the state. Zone 5a is primarily in the southern and southwestern area and zone 5b is mostly in the northwest
- Average first frost: October 13 to 21
- Best time to plant: August 29 to September 6
Zone 6
- Location: In the northwest, on the western side of the continental divide. It includes most of Sanders and Mineral counties, parts of Lake, Flathead, and Lincoln counties, and small sections of Missoula, Ravalli, and Granite counties.
- Average first frost: October 17 to 31
- Best time to plant: September 2 to 16
Check out The Best Grass Seed for Montana Lawns to foster a gorgeous green lawn.
When to plant warm-season grass
For both new and established lawns, plant warm-season grass in May or June. Wait until the soil temperature reaches 55 degrees (air temperature 65 degrees) which varies by year and location.
Note: Warm-season grasses are best suited for the warmer northwest corner of Montana, known as USDA Growing Zone 6. This includes most of Sanders and Mineral counties, parts of Lake, Flathead, and Lincoln counties, and small sections of Missoula, Ravalli, and Granite counties.
The only suitable warm-season grasses are the native buffalograss and blue grama grass.
Once you’ve established your lawn, start thinking about your landscaping. Here’s Montana Native Plants for Your Landscape for more information.
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Should I hire a professional?
Establishing a lawn and then maintaining it is relatively easy, but it’s also time-consuming and laborious. If you’re like many in Big Sky Country, you’d rather enjoy the outdoors, not maintain your lawn. Lawn Love can help. We’ll connect you with a vetted, experienced, affordable local lawn care pro. Enjoy your lawn and your weekend without breaking a sweat.
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