Because Idaho is located in the northern region of the United States, most of your cool season grasses will grow well in lawns, most notably Kentucky bluegrass and fine fescue.
Planting grass seed in Idaho can be done between the months of spring and fall but keep in mind that planting in spring may give grass a longer growing season in which to get well established, but the summer heat and weeds may cause problems. Fall seeding minimizes danger of heat injury, but allow about 6 weeks of 50° F to 70° F. Lawns seeded within a week of Labor Day are more likely to fill in completely for winter and produce a thicker turf appearance for the following spring compared to lawns seeded in Fall. You want to plant your grass seed in the late summer because the warmer temperatures, accompanied with sufficient water, will encourage good grass seed germination.
A prime grass candidate for lawns in Idaho is Kentucky bluegrass. It is considered the best quality turf grass for cooler climates and makes a fine textured lawn. It includes the ability to fill-in damaged parts without needing to reseed. Bluegrass is additionally a lot more winter-hardy compared to other cool season grass varieties. Newer varieties will be more resistant against diseases. It performs best in full sun, but could be mixed with a fine fescue to use in shady areas. Bluegrass might need one to three months to germinate and establish, based upon site conditions. It makes an outstanding athletic field. Bluegrass could be seeded or sodded for establishment.
Kentucky bluegrass planted in Idaho is often blended with other cool season grasses like perennial rye grass. Its quick establishment time frame works well with the reduced establishment time of bluegrass. It’s also a fine textured grass much like bluegrass with good drought tolerance. Not necessarily as cold tolerant as bluegrass but works well in southern Idaho lawns. Plant Kentucky bluegrass at 3 pounds per 1,000 square feet or 1.5 pounds per 1,000 square feet for over-seeding projects. Mow at 2 to 3 inches.
Fine fescue varieties are fine-leaved turf grasses that are suited well for conditions of shade, low soil moisture, low fertility, and soils with unfavorable pH levels. The fine fescues planted in sandy soils with good drainage grow best so adding a layer of sand on top of your soil surface during soil preparation can be effective. Extra applications of fertilizer, frequent irrigation or establishment on poorly drained soils can lead to a drop in quality and plant body. With ideal management, the fine fescues could make an attractive turf for your lawn. Fine fescues are seldom seeded by itself. Fine fescues are commonly found in mixtures with the other cool-season turf grasses on low maintenance or shady lawns. Plant at 5 pounds per 1,000 square feet and maintain mowing height between 3 and 4 inches.
For areas of Idaho where the winter cold may be less intense and where summers are warm, tall fescue can be a suitable alternative. Tall fescue has been used traditionally for a low-maintenance grass in places that a coarser texture is not a concern. Tall fescue can handle soils low in nutrients, grows well under low maintenance and features good tolerance to insects and diseases. Tall fescue seed germinates and establishes rapidly but a bit slower than perennial ryegrass. When fully established, tall fescue has outstanding wear tolerance and due to its deep rooting system, tolerates drought and will stay green for the duration of most Idaho summers without extra irrigation. Tall fescue seedlings will not be cold-tolerant and can die if planted too late in the season. However, well-established seedlings and fully developed lawns will withstand southern Idaho’s winters.
The best time for planting tall fescue seed in Idaho is between Aug. 25 and Oct. 10. Keep in mind that lawns seeded within a week of Labor Day are more likely to fill in completely for winter and produce a thicker, denser turf appearance for the following spring compared to lawns seeded in October. Seed at 6 to 8 pounds per 1,000 square feet under a well prepared soil.
Tall fescue grows rapidly and needs frequent mowing, especially during the summer. Mow frequently making sure not to cut off more than one third of the grass height which will prevent unsightly scalping of your grass. Apply 1-1.5 lbs/1,000 sq ft of nitrogen in September and November and in May only apply one pound of nitrogen per 1,000 square feet.
A true prairie grass with good heat and drought tolerance that is mostly established by vegetative plant parts but can be established by seed which are collected from female plants. Buffalograss is a fine textured grass that forms a dense turf with a light green color. It is not tolerant to sandy or salty soils and will not grow in shade. Buffalograss can be used for low maintenance lawns in southern Idaho and does not require a large amount of nitrogen or water. Plant at 3 lbs per 1,000 square feet. If plenty of water is supplied, buffalo grass can be cut at 1 ½ inches but for a truly low maintenance lawn, mow at 2 ½ to 3 inches during summer months.