Turfgrass Selection
Not all grasses are created equal. In Idaho, most home lawns are composed of Kentucky bluegrass, perennial ryegrass, tall fescue, fine fescue or a combination of the four. These grasses are classified as cool-season turfgrasses and are well adapted to northern regions of the U.S. They grow rapidly in the spring and fall when soil temperatures are around 55-65° F. Their growth is slower in the summer as both air and soil temperatures rises. These four grasses differ in their adaptation to shade and cold temperature, as well as in their color, texture, maintenance requirements, and growth habit.
Their are two basic growth patterns of lawn grasses, bunch-type and spreading, and the growth habit affects how quickly they spread into bare areas. Bunch-type grasses grow in clumps and spread very slowly by tillers, which are secondary stems that grow vertically from the base of the plant. Spreading type grasses, in addition to tillers, produce stems that grow horizontally either underground (rhizomes) or aboveground (stolons), and can fill in bare or damaged areas much more quickly than bunch-type grasses.
So which grass should you plant if you are establishing a new lawn, renovating or re-seeding an existing lawn? Unfortunately, the answer is, “it depends.” There are many important factors that need to be considered such as the intended use of the lawn, the amount of care it will receive, and the environment. Will it be a showcase lawn for the neighbors to admire, or will it be the type of lawn that violates your subdivisions landscape covenants? Do you have pets? Will you have lots of barbecues and foot traffic on the lawn? Once you have determined the quality level and intended use, you can choose the grass best suited to your specific needs. Even if you already have a lawn established, it is important to know what type of grass you have so that you can fine tune your management practices to best suit the needs of that particular grass.
The next sections describe the four most common lawn grasses in Idaho including information about adaptation, identification characteristics, growth habit, advantages, disadvantages, management considerations and variety selection.
Kentucky bluegrass (Poa pratensis) is the most widely adapted and most commonly used lawn grass in the United States. 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 leaves have a characteristic boat-shaped leaf tip and a prominent midrib.
Kentucky bluegrass has a spreading growth habit with aggressive rhizomes allowing it to form a dense sod and fill in bare spots quickly during establishment. These rhizomes also make it challenging for gardeners striving to keep this grass from creeping into adjacent flower beds. Additionally, this aggressive, spreading growth habit makes Kentucky bluegrass susceptible to thatch development especially under high fertility and moist conditions. Yearly aerification and prudent fertilization and irrigation practices will help keep thatch to a manageable level.
A major limiting factor of Kentucky bluegrass on home lawns is its lack of shade tolerance. Under heavy tree shade or on the north sides of houses that receive substantial shade during the day, it will thin and develop powdery mildew, a white, powdery fungus on the leaves. Raising the mowing height in shady areas will help some, by giving it more leaf area to catch light.
Kentucky bluegrass requires medium to high inputs of water and fertilizer depending on the desired quality level of the lawn. For most home lawns, Kentucky bluegrass should be maintained at a mowing height of 2 to 3 1/2 inches. Mow towards the higher end of the range to develop a deep root system. Kentucky bluegrass requires 2 to 5 lbs of nitrogen (N) per 1000 ft
Establishment from seed can be quite slow, requiring 10 to 20 days for germination. Using a straw mulch or planting a seed mixture with a small percentage of perennial ryegrass, which germinates much faster, will provide some protection for the slower germinating Kentucky bluegrass seeds. Laying sod will bypass this germination problem, but proper care during sod grow-in is just as important as proper care during seed establishment. Kentucky bluegrass sod is readily available in Idaho from garden centers and directly from sod producers.
There are many varieties of Kentucky bluegrass available giving a wide range of disease resistance, wear tolerance and green color. Most of the grass seed available at your local garden center or lawn and garden areas of major chain stores will have varieties of superior quality. Be sure to check the label of the seed package to ensure you are buying ‘named’ varieties and not ‘variety-not-stated’. Named varieties listed on the label indicate that the variety(ies) is an improved variety and has gone through several years of testing. It is best to choose a blend of three or more Kentucky bluegrass varieties to ensure a broad resistance base to diseases.
This fact sheet originally from Colorado State University outlines the positive and negative characteristics of Kentucky bluegrass as well as provides some management considerations.
Perennial ryegrass (Lolium perenne) is a bunch-type lawn grass that is commonly used in grass mixtures with Kentucky bluegrass (Poa pratensis) on home lawns and sports fields. It is very similar in color and appearance to Kentucky bluegrass.
The leaves of perennial ryegrass 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. More identifying characteristics can be found. The veiny leaves make perennial ryegrass difficult to mow especially if mower blades are not kept sharp. This leaf characteristic is also what gives perennial ryegrass the traffic tolerance for use on sports fields.
Perennial ryegrass is not as cold hardy as Kentucky bluegrass and is more prone to winter kill than Kentucky bluegrass. Perennial ryegrass is considered a short-lived perennial because of its lack of cold tolerance and it is not recommended for higher elevations of Idaho, but will do very well along the lower Snake River plains.
Perennial ryegrass germinates from seed considerably faster than Kentucky bluegrass and can overwhelm the other grasses in a mixture if there is too high of a percentage (over 20%). Perennial ryegrass will not fill in bare or damaged areas as quickly due to its bunch-type growth habit. However, an advantage is it does not form thatch due to its lack of rhizomes. Perennial ryegrass is slightly more shade tolerant than Kentucky bluegrass, but may thin out in shaded areas over time due to its lack of storage organs. It is also fairly drought resistant since it can develop a deep root system
Perennial ryegrass requires medium to high cultural practices and should be mowed between 2 to 3 inches. Remember to keep mower blades sharp to cut through the tough leaves. Fertility and irrigation requirements are similar to those of Kentucky bluegrass.
Sod is not available as pure perennial ryegrass, but many sod growers use perennial ryegrass in a mix with Kentucky bluegrass. Establishment of perennial ryegrass from seed is relatively easy due to its very quick germination rate. Seed at rates of 6 to 8 lbs per 1000 ft². As with Kentucky bluegrass, many good quality varieties are available at garden centers. Avoid selecting grass mixtures with annual bluegrass, as this grass produces a poor quality turf over time and should be used for quick, emergency use areas only to prevent soil from eroding. Make sure and select ‘named’ varieties.
Tall fescue (Festuca arundinacea)), like perennial ryegrass, is a bunch-type grass with a slightly coarser leaf texture than Kentucky bluegrass and perennial ryegrass. A description of tall fescue can be found here. However, many turf-type varieties with much finer leaves are now available. Tall fescue is gaining popularity on home lawns and is used on sports fields because its tough leaves give it good traffic tolerance.
Tall fescue is more cold tolerant than perennial ryegrass, but not as cold tolerant as Kentucky bluegrass. Be aware, though, that tall fescue may become thin in short season, higher elevation areas. It is very heat and drought resistant due to its deep, extensive root system. Tall fescue also has good shade tolerance compared with Kentucky bluegrass and perennial ryegrass. It has few insect and disease problems if managed properly. Due its bunch-type growth habit, it forms thatch slowly and does not invade flower beds, but may require overseeding on damaged or areas worn by heavy use.
Tall fescue has a wide range of cultural needs depending on use. The best quality turf is achieved at mowing heights of 2 to 3½ inches. Fertility requirements are less than Kentucky bluegrass ranging from 2 to 4 pounds nitrogen (N) per 1,000 ft² per season. The deep root system of tall fescue will allow it to draw water from deeper depths in the soil and may allow you to stretch the irrigation frequency by about a day during the summer compared with Kentucky bluegrass. However, if the root system is restricted due to poor soil conditions, tall fescue will need just as much water as Kentucky bluegrass, if not more.
Availability of tall fescue sod is more limited than Kentucky bluegrass, but seed is readily available and germination is fast. Seed at rates of 6 to 8 pounds per 1,000 ft². Many new turf-type tall fescue varieties are now available and as always, choose seed with ‘named’ varieties. 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.
The fine-leaved fescues (Festuca spp.) are generally considered low maintenance grasses because of their low nitrogen requirement and slow growth, but they can produce a dense, quality turf with proper management. The fine fescues include creeping red (Festuca rubra subp. rubra), chewings (Festuca rubra subsp. chewings) sheep (Festuca ovina) and hard (Festuca longifolia or duriuscula) fescue. All are primarily bunch-type grasses except for creeping red fescuse which has rhizomes. Fine fescues 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 not recommended for high traffic areas because their leaves do not hold up to wear like perennial ryegrass and tall fescue and they are slow to fill in damaged areas.
Leaves of the fine fescues, as their name suggests, are very narrow, resembling a pine needle. Although they are bunch-type grasses, the fine fescues will produce thatch quickly due to the chemical makeup of their leaves and stems that makes them difficult to break down.
Fine fescue leaf has a needle-like appearance.
The fine fescues 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. However, they are very cold tolerant and tolerate poor soil conditions. Mowing can be difficult for the fine fescues because the leaves tend to lay over so are missed by the mower blade. For medium quality, dense lawns, the fine fescues should be mowed closer to 2 inches and up to 2½ inches under shady areas. Fertility requirements are quite low, ranging from 1/2 to 2 lbs nitrogen (N) per 1000 ft² per year. For true low maintenance areas, sheep and hard fescue are better adapted, while under traditional home lawn conditions and in mixtures with Kentucky bluegrass, creeping red and chewings are better.
Sod is not available for the fine fescues except under special and specific conditions. Seed is readily available and several varieties are currently in use. Seeding rates should be in the range of 5 to 7 lbs per 1000 ft². Germination is fairly rapid although seedling maturation is quite slow, so frequent irrigation may need to be extended longer than for the establishment other cool-season grasses.
Buffalo grass (Buchloë dactyloides) is a warm-season grass native to the western plains of the U.S. Because it is a warm-season grass, it grows quite differently than the cool-season grasses. It 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. It turns a purple-gray color after a killing frost in the fall and will remain dormant until late spring. The leaves are hairy and gray-green in color and fine textured. Buffalo grass has a spreading growth habit with aggressive stolons that are difficult to contain.
The big advantage of buffalo grass is its excellent heat and drought tolerance as a result of its deep root system and very low water use rate. It also has a very low nitrogen fertilizer requirement and is slow growing requiring less frequent mowing. The major disadvantage of buffalo grass is its very short growing season — mid May to approximately mid September (see figure). It is not recommended for high elevation areas (>6,000 ft). Weed encroachment can be a major problem since sunlight may be able to penetrate the dormant turf, especially in thinner areas. It is not shade tolerant and does not tolerate heavy traffic.
Buffalo grass can be established from sod or plugs, but availability is very limited. Seed is also more difficult to find and is quite expensive compared with the cool-season grasses. The seed is inside of a hard burr that should be treated with a KNO3 (potassium nitrate), a non-toxic salt to help soften the seed coat and break dormancy. When seeding, it is important to ensure good soil contact and cover seeds to a depth of 1/4 to 1/2 inch. The large burr is more difficult to cover with soil, so extra care should be taken at this step with additional raking if needed. It is important to remember that buffalo grass is only drought resistant once established. New seedlings are still susceptible to drying until they can develop an adequate root system. This may take one full season to attain. Buffalo grass should be seeded in late May or early June with a mature stand possible by September.
Once established, buffalo grass should be mowed from 2 1/2 to 4 inches for a higher quality lawn. Mowing may be required only every two to three weeks. Fertilization requirements are less than 2 lbs of nitrogen (N) per 1,000 ft2 per year with applications made during the summer months, unlike the cool-season grasses. Buffalo grass requires about 1 to 2 inches of water every two to four weeks to produce acceptable quality.
Most pre-packaged seed you buy in a store will be either a mixture of several types of grasses (Kentucky bluegrass + perennial ryegrass) or a blend of several varieties of one type of grass (Kentucky bluegrass: ‘Baron’ + ‘Chateau’ + ‘Courtyard’).
Mixtures are designed to take advantage of the characteristics of several types of grasses for use in areas with varying conditions. The most common example of a mixture is a sun/shade mix. This type of seed mixture may contain Kentucky bluegrass and creeping red fescue. In sunny locations, the Kentucky bluegrass will thrive and dominate the stand, while in shaded areas the fine fescue will dominate. Perennial ryegrass is commonly added to sun/shade mixtures as a nursegrass since it germinates rapidly and provides protection for the slower emerging grasses. The percentage of perennial ryegrass in a mixture should be less than 20% so that it does not overwhelm the other grasses. Blends of several varieties of one type of grass are designed to take advantage of the desirable characteristics of each variety, for example, disease resistance. There are hundreds of varieties available for each of the grass types and blending several of these together helps guard against diseases as well as increases the environmental adaptation of the grass. Make sure to check the label when purchasing blends and avoid buying those with ‘variety not stated’ since these tend to be older, out-dated varieties.
Seed Sources
Many nurseries and home garden centers provide grass seed. A listing of nursery members of the Idaho Nursery and Landscape Association can be found at their website.