Most grasses in Idaho are cool-season grasses, with buffalograss being the only exception. The best time to plant cool-season grass seeds in Idaho is during the fall, while the best time to plant buffalograss is during the spring and early summer.
The Gem State’s climate varies significantly from southern to northern Idaho, so if you plan to seed your lawn, timing is everything. We’ll explore these important details and more in this article.
When to plant cool-season grasses in Idaho
Idaho falls in USDA plant hardiness zones 3-7, so the best grass seeds for Idaho lawns are mostly cool-season grasses. Cool-season grasses in Idaho do best if they are planted during the fall.
By seeding during the fall season, you avoid planting right before the hot, dry summer and give your new grass plenty of time to store nutrients before spring. There are also fewer weeds to compete with your grass during the fall. (Summer annual weeds are stiff competition for new grass seedlings.)
If you aren’t able to plant your cool-season grass in the fall, there’s still hope. The second-best time to plant a cool-season lawn is in spring, but be prepared to pay closer attention to watering and weed control.
Here are the best cool-season grasses for Idaho lawns and when to plant them:
Kentucky bluegrass
Kentucky bluegrass (KBG) is a cool-season grass that grows in USDA zones 2-6. It is fairly high-maintenance, doesn’t do well in the shade, and is vulnerable to common Kentucky bluegrass lawn diseases and thatch. Because of this, it’s often mixed with perennial ryegrass seeds to create a more substantial turf.
The best time to plant KBG seed is fall, from September to November, and spring, from February to May. However, if you plan to plant an 80% KBG, 20% perennial ryegrass (PRG) mixture, don’t worry. They’re both cool-season grasses, so their seeding schedules intersect.
To learn more about this grass, read our guide on Kentucky Bluegrass: How to Grow and Care for It.
Grass Seed Options:
– Jonathan Green (11970) Blue Panther Kentucky Bluegrass Grass Seed (3 lbs.)
– SeedRanch Midnight Kentucky Bluegrass Seed (5 lbs.)
Perennial ryegrass
A cool-season bunch-type grass found in USDA zones 3 to 7, perennial ryegrass makes itself at home in northern, southern, and central Idaho. When planted on its own, this grass is high-maintenance, becoming vulnerable to any extreme hot or cold temperature and unable to repair itself. For these reasons, perennial ryegrass is often mixed with other grasses
Despite these challenges, perennial ryegrass has a few things going for it, like it provides a much faster cover than KBG, thanks to its quick germination time. It also makes lush, gorgeous lawn stripes when it’s mowed and cared for properly. You can also easily repair any damage to the grass by simply reseeding the injured patches.
Whether you’re establishing a new lawn or repairing an existing one, perennial ryegrass should be seeded in spring from March to early May or during early fall from mid-August to early September.
For more information on this cool-season beauty, check out our article on Perennial Ryegrass: How to Grow and Care for It.
Grass Seed Options:
– Outsidepride Perennial Ryegrass Seed (5 lbs.)
– Eretz ProTurf Perennial Ryegrass Fine Lawn Seed (choose your size)
Tall fescue
Tall fescue is a cool-season grass found in USDA zones 4 to 7, and if grown in good-quality soil with good drainage, it can develop an extensive root system that gives it an advantage against heat and drought.
Tall fescue germinates best when the soil temperature is between 59-72 degrees and can be seeded in either fall or spring. To learn more about this drought-resistant grass, our comprehensive guide to tall fescue will explain how to plant and grow a beautiful tall fescue lawn.
Grass Seed Options:
– Triple-Play Tall Fescue Grass Seed Blend (5000 sq ft)
– Eretz Kentucky 31 K31 Tall Fescue Grass Seed (choose your size)
– Pennington The Rebels Tall Fescue Grass Seed Mix (7 lb.)
Fine fescue
Fine fescues are a group of four cool-season grasses known for being low-maintenance and shade-tolerant. They are often mixed with perennial ryegrass or Kentucky bluegrass. These grasses have fine, needle-like grass blades; are sensitive to heat; go dormant during the summer; and are slow to recover from heavy foot traffic.
Common fine fescues found in Idaho are:
- Chewings fescue (Festuca rubra subsp. commutata)
- Creeping red fescue (Festuca rubra subsp. rubra)
- Hard fescue (Festuca longifolia or duriuscula)
- Sheep fescue (Festuca ovina)
Fine fescues can be found in a wide range of hardiness zones and work well in any climate that is suited for cool-season grass, so they are perfect for Idaho. To establish a fine fescue lawn, seed during late summer or early fall unless you live in a highly elevated area like Island Park or Sun Valley, in which case you should seed in spring or early summer.
Grass Seed Options:
– Outsidepride Legacy Fine Fescue Grass Seed (5 lbs.)
– Eretz Creeping Red Fine Fescue Seed (choose your size)
– Outsidepride Creeping Red Fine Fescue Grass Seed (25 lbs.)
When to plant warm-season grasses in Idaho
The best time to plant warm-season grasses is during the spring and early summer when the soil temperatures are consistently above 55 degrees and there is no longer a risk of frost.
The downside of planting during this time is that your new grass will be more exposed to hot conditions, leaving it vulnerable to disease, drought, and weeds. On the plus side, your warm-season grass seed will also get the benefits of warm temperatures so it has time to establish before the fall.
Here is the best warm-season grass for Idaho:
Buffalograss
Found in USDA zones 5-8, buffalograss is the best warm-season grass for Idaho because it has no trouble surviving freezing Idahoan winters despite its warm-season status, which also gives it an advantage against heat and drought in the summer months. To learn more about this native Great Plains grass, read our guide on Buffalograss: How to Grow and Care for It.
For the best results, buffalograss seeds should be planted during late May to early June.
Grass Seed Options:
– Everwilde Farms Buffalograss Seeds (1 lb. of seeds)
– Buffalograss seed (primed) (5-lb. bag)
How to seed your Idaho lawn
Once the time has come to plant your grass, you’ll need to know how to plant grass seed and establish your new lawn successfully. Here are the steps to seeding your new Idaho lawn:
- Start by choosing the right seed for your lawn and location. Every grass type has its own strengths and weaknesses and may not be suitable for your lawn or your area in Idaho.
- Clean the area where you want to plant. Remove rocks, tree branches, debris, and weeds. This will ensure you have soil that’s free from obstructions and perfect for germination.
- Prepare the soil by aerating before applying compost and fertilizer as needed.
- Use a broadcast spreader to seed the lawn. Fill half the spreader with seed and walk back and forth until you’re finished. Then fill the other half and walk back and forth perpendicular to your original direction.
- Cover the area with straw mulch. This will keep the seed safe from birds and heat.
- Lightly water 2 to 3 times daily. Keep watering your grass seed often until the seedlings are 1 inch tall.
- Gradually reduce watering the grass until you get to the recommended watering schedule for your chosen grass.
Overseeding your Idaho lawn
If you already have a lawn but notice bare, thinning patches, you will need to start overseeding those bald spots.
Since peak growing seasons and germination are the same regardless of what you plan to do with your grass seeds, overseeding should take place at the same time you would plant them from scratch.
Here’s a chart to help make timing it simple:
| Grass type | Outside temperature | Months |
| Cool-season grass | Between 60° and 75°F | Late summer – Early fall |
| Warm-season grass | Between 70° and 90°F | Late spring – Early summer |
Here’s how to overseed your lawn:
- Mow your grass to about 1 ½ to 2 inches so the seeds can reach the soil.
- Dethatch, aerate and fertilize as needed so that the soil is healthy.
- Spread your preferred grass seed.
- Regularly water your lawn.
FAQ about planting grass seed in Idaho
How can I protect my landscape from wildfires?
Preparing a defensible space around your home is the most important way to protect your landscape and home from wildfires. It starts by developing zones around your house:
- Ember-resistant zone: The area closest to your home (0-5 feet away from the building) should be cleared of all combustible materials to reduce the risk of flames coming into contact with your home.
- Lean, clean, and green zone: At 5-30 feet from the house, this zone should lessen the risk of the fire spreading. Remove all dead and decaying vegetation and keep enough space between trees and shrubs.
- Reduce fuel zone: The furthest away from your building (30-100 feet), this zone should reduce potential fuel for the wildfire. Keep your lawn trimmed, keep trees and shrubs spaced, remove debris, and make sure there’s 10 feet of bare soil around any wood piles.
For a detailed guide on how to protect your home, see our article on How to Create Fire-Resistant Landscaping.
Can I plant Idaho fescue on my lawn?
Yes, you can plant Idaho fescue (Festuca idahoensis), but Idaho fescue is a forage grass that is perfect for livestock and erosion control. It doesn’t have any appeal as a lawn grass.
How long before you can walk on grass seed?
You can walk on your new grass after you’re done seeding when it reaches a normal mowing height. It’s perfectly fine for you to rake up the hay and even mow only a week after, however, so long as the grass is at its normal mowing height or just a bit shorter.
Hire a Pro
Overseeding, mowing, irrigating, and maintaining your lawn are no small potatoes! Let Lawn Love connect you with lawn care professionals in your area for all of your lawn care needs. That way, you can maintain your lush lawn no matter what grass type you have.
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Main Image Credit: Jose and Gertrude Anasola House | Drmccreedy | Wikimedia Commons | CC BY-SA 4.0
