5 Types of Grass in Idaho and How to Tell Which You Have

Some of the Kentucky bluegrass seed sold for lawns is grown in northern Idaho. A University of Idaho Extension bulletin on Kentucky bluegrass production, published in 2005, reported that seed growing in northern Idaho "began during the 1950's with approximately 10,000 acres and has since grown to 70,000 acres," and that "Idaho produces 50 percent, and the tri-state region (Idaho, Washington, and Oregon) produces 90 percent of the total U.S. Kentucky bluegrass seed," citing a 1978 study and the 1997 Census of Agriculture. Those are historical figures, not this year's, but they make the point: Idaho is not just a place where bluegrass lawns happen to work. It has been one of the places the seed comes from.

That does not mean bluegrass is right for every yard in the state. Idaho runs from 738 feet at the Clearwater and Snake confluence up past 12,000 feet, and University of Idaho Extension sorts its lawn advice by elevation instead of by region. Perennial ryegrass "is not recommended for higher elevations of Idaho but will do very well along the lower Snake River plains." Tall fescue "may become thin in short season, higher elevation areas." Same seed rack in Boise and in Driggs, very different outcomes. Here are the grasses, how to tell them apart, and where each one actually holds up.

The types of grass that grow in Idaho

Kentucky Bluegrass

Kentucky bluegrass is the Idaho default, and CIS 1062 says so plainly: it "is the most widely adapted and used lawn grass in Idaho." U of I says it "does well in sunny areas throughout Idaho, is very cold tolerant, and will form a dense, high-quality turf when grown in full sunlight." The tell is in the leaf: "The leaves have a characteristic boat-shaped leaf tip and a prominent midrib." Bluegrass spreads by rhizomes, so it fills its own bare spots, and U of I notes the same habit "makes Kentucky bluegrass susceptible to thatch development." Those rhizomes are also, in U of I's words, "challenging for gardeners striving to keep this grass from creeping into adjacent flower beds." The real limit is shade, not cold. U of I calls lack of shade tolerance "a major limiting factor of Kentucky bluegrass on home lawns," and under heavy tree shade or on a north wall it thins and picks up powdery mildew. It is also the thirstiest of the group. CIS 1062 says "bluegrass requires the most water and fertilizer of all grasses," which works out to 2 to 5 pounds of nitrogen per 1,000 square feet a season, but it survives a dry stretch by going dormant rather than dying, "as long as it is allowed to properly harden prior to the drought." One Idaho quirk worth knowing: billbugs are "perhaps the most common insect affecting home lawns in Idaho," and U of I says Kentucky bluegrass "is particularly susceptible to these insects," though it adds that "in high altitude areas above 5,000 feet billbugs are not found at very high densities."

Perennial Ryegrass

Perennial ryegrass is the grass that makes Idaho advice elevation-dependent. U of I calls it "a short-lived perennial because of its lack of cold tolerance," and then draws the line explicitly: it "is not recommended for higher elevations of Idaho but will do very well along the lower Snake River plains." In Boise, Nampa or Lewiston it is a legitimate part of a lawn. In the high valleys it is a passenger. The short-season bulletin says it "should not be used as a stand-alone grass for home lawns in short-season, high-altitude areas" and lists it in its table with the note "use only in seed mixes as a nurse grass," because "Kentucky bluegrass will eventually crowd out any perennial ryegrass plants that may survive the cold temperatures of these areas." What it does at any elevation is come up fast. CIS 1062 says bluegrass can take three weeks to appear while ryegrass can be up in six days, which is what makes it useful in a seed mix. Keep the share small: U of I warns it "can overwhelm the other grasses in a mixture if there is too high of a percentage (over 20%)." To identify it, look at the upper leaf surface. Ryegrass leaves "do not have the boat-shaped leaf tip like Kentucky bluegrass, instead have a pointed tip with veins on the top side of the leaves that are very conspicuous." U of I says those veiny leaves "make perennial ryegrass difficult to mow especially if mower blades are not kept sharp," and advises keeping blades sharp "to cut through the tough leaves."

Tall Fescue

Tall fescue is the deep-rooted option, and the one most often oversold. U of I describes it as a bunch-type grass "with a slightly coarser leaf texture than Kentucky bluegrass and perennial ryegrass" that is "very heat and drought resistant due to its deep, extensive root system" and has "good shade tolerance compared with Kentucky bluegrass and perennial ryegrass." U of I also says it "is used on sports fields because it's tough leaves give it good traffic tolerance." What it does not do is cut your water bill. U of I says the deep roots "may allow you to stretch the irrigation frequency by about a day during the summer compared with Kentucky bluegrass," and CIS 1062 is blunter: "Contrary to widely publicized claims, research shows that tall fescue needs as much water over the growing season as Kentucky bluegrass; tall fescue simply needs more water at less frequent intervals." Fewer, deeper soakings, not less water. The Idaho catch is cold and snow. U of I warns that tall fescue "may become thin in short season, higher elevation areas," and the short-season bulletin goes further: it "is not recommended for high snowfall areas or elevations where extended, cold winters are common, because it is intolerant of cold temperatures and is very susceptible to snow mold." The same bulletin gives it a specific eastern Idaho landing zone, noting it "has performed well in eastern Idaho at the warmest edges of high-elevation zones (4,000 to 4,500 ft)." It does take less feeding than bluegrass, 2 to 4 pounds of nitrogen per 1,000 square feet a season, and CIS 1062 credits it with "excellent persistence even in high pH soils," which matters on southern Idaho ground. One buying rule from U of I: "Avoid the variety K-31 or Kentucky 31 as this is the old forage-type variety with wide blades and will result in a poor-quality lawn."

Fine Fescue

Fine fescues are the shade specialists and the high-country favorites. The group covers creeping red, chewings, sheep and hard fescue, and U of I says they are "the most shade tolerant of the cool-season grasses and are commonly used in shade mixtures with Kentucky bluegrass and/or perennial ryegrass." They are also the lowest-input group of the four, "generally considered low maintenance grasses because of their low nitrogen requirement and slow growth," at half a pound to 2 pounds of nitrogen per 1,000 square feet a year. For Idaho mountain towns the short-season bulletin makes them the headline pick: fine fescues are "perhaps best suited to high-altitude climates because of their ability to survive very cold temperatures and their low nitrogen requirement." The trade is heat, not cold. U of I says they are "very drought resistant, but do not tolerate heat very well and may go dormant in the middle of the summer when temperatures reach into the 90s even under well-watered conditions," which is exactly the Treasure Valley and Magic Valley summer. They also will not take a beating: "not recommended for high traffic areas because their leaves do not hold up to wear." Two surprises for owners. Despite being bunch-type grasses they "will produce thatch quickly due to the chemical makeup of their leaves and stems that makes them difficult to break down." And they are awkward to cut, because "the leaves tend to lay over, so they are missed by the mower blade." You will usually meet them inside a blend, where the needle-thin blades give them away.

Buffalograss

Buffalo grass is the honest low-water answer, and U of I is equally honest about the cost. It is a warm-season native that "grows slowly in the spring and fall and will go dormant for up to seven months of the year in Idaho and other northern parts of the U.S.," turning "a purple-gray color after a killing frost in the fall." CIS 1062 puts the tradeoff in plain numbers: buffalo grass dormancy "results in Kentucky bluegrass having about six more weeks of green color at each end of the growing season." What you get back is real. U of I calls out "its excellent heat and drought tolerance as a result of its deep root system and very low water use rate," a "very low nitrogen fertilizer requirement," and slow growth so you mow every two to three weeks instead of weekly. It gets by on "about 1 to 2 inches of water every two to four weeks." It is also picky about where it goes. U of I names its growing season as roughly mid-May to mid-September, says it "is not recommended for high elevation areas (>6,000 ft)," and warns it "is not shade tolerant and does not tolerate heavy traffic," with weeds moving into the dormant turf when sunlight reaches the soil. Identify it by color and calendar. The leaves are "hairy and gray green in color and fine textured," and CIS 1062 says it "looks somewhat like Kentucky bluegrass, but with finer leaves that are not as dark green." Unlike everything else on this list it spreads by aboveground stolons, and it is still dormant in spring when the bluegrass lawns nearby are already growing.

A few grasses come up in Idaho conversations and should not. On the warm-season side, CIS 1062 says "southern-type, warm-season grasses such as bermudagrass and zoysiagrass survive in Idaho but are dormant and brown for up to eight months of the year," while "st. augustinegrass and dichondra, should not be planted in Idaho lawns because they do not survive in our cool climate." On the utility side, the wheatgrasses come up constantly around cabins and acreages. U of I lists crested, western, Siberian, streambank and bluebunch wheatgrass as good for erosion control at elevations up to 10,000 feet and in areas under 14 inches of precipitation, but says flatly that they "are not recommended for use in lawns because most are wide-bladed and produce a thin stand, and also undergo summer dormancy." The same bulletin notes that "the fine fescues, including Idaho fescue, can also function to prevent soil erosion and are much shorter in stature," which is usually the better answer for the strip between the cabin and the driveway.