Cool-season turfgrasses include species that are adapted to the cooler portions of the United States and make maximum growth during cool spring and fall weather. They may become semi-dormant during hot and/or dry periods of summer. Cool-season grasses adapted for turf use in Pennsylvania include Kentucky bluegrass, rough bluegrass, perennial ryegrass, the fine fescues, tall fescue, and the bentgrasses.
Warm-season turfgrasses include species that are best adapted to southern areas of the United States. Some of the warm-season turfgrasses also are adapted to the transitional regions between the northern and the southern states. These grasses make maximum growth during hot weather and are dormant during late fall, winter, and early spring. Zoysiagrass is the only warm-season turfgrass that has sufficient winter hardiness to survive and persist as high-quality turf in the southern-most portions of Pennsylvania.
Turfgrass species vary in their adaptation to soil moisture, temperature extremes, soil fertility, pH levels, disease and insect resistance, wear tolerance, and mowing tolerance. They may also vary in such characteristics as leaf texture, color, growth habit, density, growth rate, and uniformity. Considerable variation in these attributes can also occur within an individual species. Turfgrasses which exhibit characteristics that differ from other members of the same species are called varieties or cultivars.
Characteristics that plant breeders search for or incorporate into turfgrasses may include improved tolerances to climatic extremes, increased tolerance to reduced fertility levels, resistance to diseases and insects, and better wear and mowing tolerances. Breeders also search for plants that exhibit medium to fine leaf textures, an aesthetically-pleasing color, a decumbent growth habit, increased recuperative potential, good density, and uniformity. Ability to produce good seed yields is also an important consideration in developing improved turfgrass varieties.
Kentucky Bluegrass (Poa pratensis)
Kentucky bluegrass is a persistent and attractive species that is used in many home lawns, institutional grounds, parks, and athletic fields. This species has a medium to fine leaf texture and a medium- to dark-green color when properly fertilized. It produces extensive underground stems, called rhizomes, which provide good sod-forming characteristics and superior recuperative potential when compared to most other cool-season turfgrasses. Kentucky bluegrass is cold tolerant, wear tolerant, and moderately heat and drought tolerant. It makes optimum growth during the spring and fall and becomes semi-dormant under prolonged periods of heat and drought. It usually recovers quickly from dormancy with the advent of cooler temperatures and adequate soil moisture.
Kentucky bluegrass performs best when grown in well-drained soils and open, sunny areas. This grass does not tolerate poorly-drained soils or heavily-shaded conditions (although a few varieties have improved shade tolerance).
Kentucky bluegrass generally requires a higher amount of nitrogen (N) fertilizer (2.0 to 4.0 lb N/1,000 sq ft per growing season) than other cool-season turfgrasses and tends to produce a significant amount of thatch. In most cases, Kentucky bluegrass should be maintained at 1.5 to 2.5 inches in height. However, during hot and humid conditions the mowing height should remain at or above 2.0 inches. The germination and establishment period for Kentucky bluegrass is slower than for most other turfgrasses, requiring up to two weeks for emergence.
Some of the more damaging diseases of Kentucky bluegrass are leaf spot, dollar spot, stripe smut, necrotic ring spot, and summer patch.
Some commercial seedlots have 'common Kentucky bluegrass' printed on the label. Common Kentucky bluegrass is a nonpedigree form consisting of many genetically different types. An upright grower, it is sensitive to low mowing heights and very susceptible to leafspot diseases. The use of common Kentucky bluegrass may be justified where turf of high quality is not required and the height of cut will be at least two inches. Unfortunately, seed laws permit named varieties of Kentucky bluegrass to be sold as common Kentucky bluegrass. Some named varieties develop turf inferior to that of nonpedigreed Kentucky bluegrass but are extremely high seed yielders. For this reason, some seed producers grow and market named varieties ascommon Kentucky bluegrass.
Rough Bluegrass (Poa trivialis)
Rough bluegrass is similar to Kentucky bluegrass in appearance, however, it has a lighter-green color and produces above-ground stems called stolons that allow it to spread and generate new tillers. It is a highly shade-tolerant species that prefers moist soils. It is used in lawns with shaded conditions where there is adequate or excess moisture. When used in well-drained, open, and sunny areas, it normally will decline during the hot, dry months of summer but may recover in cool, wet weather.
Rough bluegrass normally requires 2.0 to 3.0 lb N/1,000 sq ft per growing season and tolerates mowing heights of 1.5 to 2.5 inches. Because of its light-green color and tendency to form patches, it is generally not used in mixtures with other turfgrasses.
Perennial Ryegrass (Lolium perenne)
Perennial ryegrass is a persistent, dark-green, fine to medium-textured turfgrass that is used for home lawns, parks, grounds, golf courses, and athletic fields. This species produces a bunch-type growth habit and does not form rhizomes or stolons. Its recuperative potential is not as strong as Kentucky bluegrass. Perennial ryegrass germinates rapidly (5 to 7 days) and establishes quickly. It is very competitive with other turfgrasses and is used extensively for overseeding thin or damaged turf. Because of its aggressive nature, perennial ryegrass is generally not used in amounts over 20 percent in a mixture with other turfgrasses. It is suitable for use alone or in combination with Kentucky bluegrass and/or fine fescues.
Perennial ryegrasses is wear tolerant and heat tolerant. It is only moderately tolerant of shade and drought. This species will withstand low temperatures, however, it tends to be susceptible to ice damage. Perennial ryegrass performs best on moderate to high-fertility soils and well-drained soils.
Improved varieties of perennial ryegrass have good characteristics for mowing, although some may have leaves that shred and form a gray cast when cut with dull mowers. Suggested mowing heights for the improved perennial ryegrass varieties are from 0.75 to 1.0 inch on golf course fairways to 1.5 to 2.5 inches for other turf uses.
In Pennsylvania, perennial ryegrass usually responds well to about 3.0 lb N/1,000 sq ft per growing season. When grown in infertile soils or on soils of low pH, ryegrass may become thin and clumpy. Thatch formation in perennial ryegrass turf is slower than with Kentucky bluegrass and the fine fescues.
The diseases which are most damaging to perennial ryegrass include brown patch, Pythium blight, dollar spot, red thread, and rust. Perhaps the most significant improvement in perennial ryegrass within the past few years has been the development of varieties with enhanced endophyte performance. Endophytes, in this case, are beneficial fungi that reside within the seed and grow and persist in the developing plant. Endophytes produce compounds that discourage leaf and stem-feeding insects from destroying the plant. Ryegrasses containing endophytes have shown increased resistance to sod webworms, billbugs, fall armyworms, chinch bugs, and green bugs.
The Fine Fescues (Festuca spp.)
- Creeping Red Fescue - Festuca rubra
- Chewings Fescue - Festuca rubra var. commutata
- Hard Fescue - Festuca longifolia
- Sheep Fescue - Festuca ovina
The fine fescues are composed of narrow-leaved species in the genus Festuca. The most common turf-type fine fescues include creeping red fescue (Festuca rubra), Chewings fescue (Festuca rubra var. commutata), hard fescue (Festuca longifolia), and sheep fescue (Festuca ovina). These species are used extensively for lawns, grounds, and parks. They are ideal for low maintenance turfs, but, are not typically used for sports turfs. During cool weather (and when properly maintained), the fine fescues produce an attractive, uniform stand with a medium-green to dark-green color. These grasses are extremely fine-textured and are compatible in mixtures of most cool-season turfgrasses. As a group, the fine fescues tolerate soils of low fertility and low pH, droughty soils, and shaded conditions. They are not well adapted to hot, humid conditions; poorly drained soils; high-traffic areas such as athletic fields or playgrounds; and high rates of nitrogen fertilizer. Like Kentucky bluegrass, the fine fescues become semi-dormant under prolonged periods of heat and drought and recover quickly with the advent of cooler temperatures and adequate soil moisture.
The suggested rates of nitrogen fertilizer for fine fescues are 1.0 to 2.0 lb N/1,000 sq ft per growing season. Fine fescues perform well when mowed at 2.0 inches or above. They tend to produce a significant amount of thatch and generally require periodic dethatching. Diseases that can severely damage the fine fescues include leaf spot, red thread, and dollar spot.
Creeping red fescue produces rhizomes, thus, allowing it to fill in thin areas of turf and to make good recovery from injury. This species has good seedling vigor when compared with hard and sheep fescues. Chewings fescue lacks strong rhizome development but has increased tolerance for low mowing. Hard fescue has received much attention in recent years for its tolerance of low fertility soils and drought. It has a dark-green color and good density once established. The major disadvantage of hard fescue is its relatively slow germination and rate of establishment. Sheep fescue is a bunch-type grass used primarily in low maintenance situations. Sheep fescue is used the least of the turf-type fine fescues.
Tall Fescue (Festuca arundinacea)
Tall fescue is a persistent and durable plant that forms acceptable turf for home lawns, grounds, parks, playgrounds, and athletic fields. It is commonly used in low maintenance situations such as utility areas, highway medials, airstrips, and fairgrounds. Many new and improved varieties have finer texture, higher tiller densities, and a darker-green color than the coarse-textured, light-green varieties such as 'Kentucky 31' and 'Alta.' Tall fescue is considered by many individuals to be incompatible with the finer-textured and darker-green Kentucky bluegrass, perennial ryegrass, and fine fescues. Tall fescue may be objectionable in a mixture with fine-textured turfgrass species because it tends to form coarse-textured clumps in an otherwise uniform stand.
Tall fescue is primarily a bunch-type grass that occasionally produces short rhizomes. It is somewhat slow to establish extensive root systems and has only fair recovery potential. This species is the most heat and drought tolerant of the cool-season turfgrasses. The increased drought tolerance is a function of its ability to produce a deep root system. Tall fescue performs well in open, sunny areas and is moderately shade tolerant. It is less suited to heavily-shaded conditions than the fine fescues, but is more shade tolerant than Kentucky bluegrass and perennial ryegrass. Tall fescue is best suited to well-drained soils.
Tall fescue thrives under moderate fertility levels and generally performs adequately when fertilized with 2.5 to 3.0 lb N/1,000 sq ft per growing season. Thatch development is minimal with this species and suggested mowing heights range between 2.0 and 3.0 inches.
The most serious disease of tall fescue is brown patch. This disease occurs in the hot, humid months of summer and is especially severe when the turf is heavily fertilized with nitrogen fertilizer. Other damaging diseases of tall fescue are net blotch, red thread, rust, and Pythium blight.
Dwarf-type tall fescue varieties are currently in demand for their reduced growth rates and increased tiller densities. Although some of these varieties are being used successfully in some areas of Pennsylvania, the reduced rate of growth may slow recovery from disease, insects, and/or wear. Several tall fescue varieties show endophyte-enhanced resistance to various leaf and stem feeding insects.
Bentgrasses (Agrostis spp.)
- Creeping bentgrass (Agrostis palustris)
- Colonial bentgrass (Agrostis tenuis)
Bentgrasses are fine- to medium-textured grasses that have a light to medium-green color. These species are used primarily for golf course greens and fairways, bowling greens, and grass tennis courts. They are not suitable as lawn grasses under normal maintenance regimes and are not compatible in mixtures with other cool-season grasses. Creeping bentgrass, the most commonly used bentgrass, spreads by stolons and is a prolific thatch producer. As a group, the bentgrasses are cold and heat tolerant but only moderately wear and drought tolerant. Growth is optimum during the spring and fall of the year. These grasses tolerate acidic and wet soils better than the other cool-season turfgrasses.
Bentgrasses are very susceptible to injury from a number of herbicides, making weed control difficult. They are also highly susceptible to a number of diseases including dollar spot, brown patch, Pythium blight, and take-all patch.
The amount of nitrogen that should be applied to creeping bentgrass varies depending on the desired response of the turf. Rates may vary from 2.0 to 4.0 lb N/1,000 sq ft per growing season. Bentgrasses will tolerate extremely low mowing heights (3/16-3/4 inches) provided that proper management practices are followed. Low-cut bentgrasses require irrigation, fungicide and insecticide spray application, mechanical brushing and thinning, and periodical topdressing to prevent thatch formation.
Zoysiagrass - (Zoysia japonica)
Zoysiagrass is a warm-season species that makes optimum growth during high-temperature periods. It can form an attractive turf in the southern portions of the state and is used primarily for home lawns. Zoysiagrass has a medium to fine leaf texture and tends to have a light to medium green color. This species produces extensive, thick, stolons that spread rapidly. Because of its prolific stolon production, zoysiagrass has good recuperative potential, however, it may also spread into areas where it is unwanted.
Although drought-tolerant when established, zoysiagrass performs best under moderate moisture levels on fertile, well-limed soils. It will not tolerate poorly -drained soils. Its green color is completely lost with heavy fall frosts, and plants remain dormant until late spring or early summer. Due to its relatively short growing season, zoysiagrass is suggested only for the southern-most regions of Pennsylvania.
Zoysiagrass performs well under low rates of nitrogen fertilizer. In most cases, 1.0 to 2.0 lb N/1,000 sq ft per growing season is all that is required. The best time to fertilize this species is in mid to late spring and in mid-summer. Zoysiagrass should be mowed at lower heights than most other turfgrasses used in Pennsylvania with the suggested height of cut at approximately 1.0 inch. Because zoysiagrass produces extensive amounts of thatch, dethatching should take place on a frequent basis.
Meyer zoysiagrass is the only variety suggested for Pennsylvania. It must be propagated vegetatively by planting sod plugs or sprigs. Development rate depends on plug size, competition from other grasses and weeds, and the growing environment. Quickest establishment is with 4-inch diameter plugs planted in late spring or early summer. Three to six years may be required to develop a solid stand of Meyer zoysiagrass. Cost of establishment of this grass is relatively high.
Adapted by Peter Landschoot, professor of turfgrass science, from Extension Circular 346, Turfgrasses for Pennsylvania, by John C. Harper II, professor emeritus of agronomy.