Chapter 10- Turfgrass Management in Tennessee

Authors

• Tom Samples, Retired Professor & Extension Specialist, University of Tennessee
• Mannie Bedwell, Extension Agent, University of Tennessee
• Rebecca Bowling, Assistant Professor & Extension Specialist, University of Tennessee
• Jim Brosnan, Professor & Extension Specialist, University of Tennessee
• Natalie Bumgarner, Associate Professor & Extension Specialist, University of Tennessee
• Frank Hale, Retired Professor & Extension Specialist, University of Tennessee
• Booker Leigh, Retired Extension Agent, University of Tennessee
• Mitchell Mote, Extension Agent, University of Tennessee
• Alan Windham, Retired Professor & Extension Specialist, University of Tennessee

Turf care starts with selecting a species or variety well adapted to local growing conditions, followed by using effective practices for establishing and maintaining lawns. This chapter presents the turfgrass species most commonly used in home landscapes throughout Tennessee, and it describes practices and activities for improving the overall performance and persistence of lawn grasses. Common turfgrass diseases, insect pests, and weeds are also presented.

Selecting the Right Turfgrass

Turfgrasses are grouped according to the daytime air temperatures at which they grow best. Warm-season turfgrasses grow best at air temperatures from 80° to 95°F, while cool-season turfgrasses prefer air temperatures from 60° to 75°F. (see adjacent graphs.)
Bermudagrass (Cynodon dactylon) and zoysiagrass (Zoysia spp.) are the primary perennial warm-season turfgrasses managed in home lawns in Tennessee. However, centipedegrass (Eremochloa ophiuroides) is also gaining in popularity in western Tennessee. These species generally lose color in the fall, are dormant in winter, and resume growth each spring.
The amount of damage warm-season turfgrasses suffer during late fall, winter, and early spring depends on several factors, including the actual freezing temperature encountered, the length of time the soil remains frozen, the amount of soil moisture at the time the soil freezes, the depth to which the soil freezes, the level of shade, and the exposure (for example, sloping toward the north, south, east, or west).
In Tennessee, tall fescue (Festuca arundinacea), fineleaf fescues (Festuca spp.), and Kentucky bluegrass (Poa pratensis) are the primary perennial cool-season species. These turfgrasses are often stressed in summer. Much like the amount of injury warm-season turfgrasses suffer during cold temperatures, the amount of damage to cool-season turfgrasses during summer months also depends on several factors including the air temperature, duration of extreme high temperatures and drought, relative humidity, shade level, wind speed, and direction of slope.

Adaptation

Tennessee is 440 miles wide from east to west and is partitioned into six natural land regions.

West Tennessee

The Gulf Coastal Plain Region is the largest of the natural land regions. This region is made up of three sections:

1. a hilly easternmost section about 10 miles wide and adjacent to the western edge of the Tennessee River;
2. the Tennessee Bottoms that extend to Memphis, ending as cliffs bordering the Mississippi River; and
3. the Delta, which is less than 300 feet above sea level.

Bermudagrass, centipedegrass, and zoysiagrass varieties are usually very well adapted to well-drained, full-sun sites within this region. Some cool-season species may be successfully managed in partially shaded areas.

Middle Tennessee

The Highland Rim Region is an elevated plain that surrounds the Nashville Basin Region. In this region, cool-season turfgrasses often outperform the variety known as ‘Arizona Common’ bermudagrass and other varieties of bermudagrass prone to winter kill. Although dormant in late fall, winter, and early spring, low-temperature-tolerant bermudagrass, centipedegrass, and zoysiagrass varieties are often well adapted.
The Nashville Basin Region, sometimes referred to as the Central Basin Region, starts about 60 miles east of Nashville and extends to about 80 miles south of Nashville, very near the Alabama state line. Many varieties of both warm- and cool-season turfgrasses grow well in the rich, fertile soils of this region, especially in full sun.

East Tennessee

Three major natural regions comprise East Tennessee. They are, from east to west,

1. the Blue Ridge Region;
2. the Appalachian Ridge and Valley Region; and
3. the Cumberland Plateau Region.

The Blue Ridge Region averages 5,000 feet above sea level. Although bermudagrass, centipedegrass, and zoysiagrass varieties with improved low-temperature hardiness may be grown in this region, these species are prone to winter kill during severely cold months.
The Appalachian Ridge and Valley Region extends west from the Blue Ridge Region for more than 50 miles. The ridges surrounding valleys are often forested. Valleys become broader and ridges are lower in the westernmost section of this region known as the Great Valley. Generally, cool-season turfgrasses are preferred. Although bermudagrass, centipedegrass, and zoysiagrass varieties with improved low-temperature tolerance may also be grown, they are often injured by severely low temperatures and sequential frosts.
Mountains in the Cumberland Plateau Region usually reach a height of 1,500 to 1,800 feet above sea level. Generally, cool-season species are preferred at the higher elevations. Although warm-season species on the mountains may suffer low-temperature injury during winter, both warm- and cool-season species can be managed as turf in the sharp valleys and basins.

The Right Conditions

Bermudagrass, zoysiagrass, and centipedegrass grow best at air temperatures from 80° to 95°F. These warm-season species are dormant and may suffer low-temperature damage in winter.
Air temperatures from 60° to 75°F promote the growth of tall fescue, fineleaf fescues, and Kentucky bluegrass. These cool-season species often suffer heat and drought stresses in summer.

Shade

Light is essential as a source of energy for green plants, including trees and turfgrasses. Other than St. Augustinegrass and the fineleaf fescues that have a high level of shade tolerance (as indicated in Table 1), most turfgrasses in Tennessee perform best in open areas of the landscape receiving full sun. Turfgrasses growing in very low light become spindly and succulent, and they have few tillers compared to the same species and varieties grown in full sun.
When determining whether there is enough light to sustain a particular turfgrass species or variety, it is important to consider light intensity, quality, and duration. Shading reduces light intensity, alters light quality, and subsequently lowers daytime temperatures. In addition to reducing dew formation, a tree canopy may seriously restrict air movement over the turf surface. Also, the relative humidity and carbon dioxide content of air are often elevated in a shaded environment. Heavily shaded turfs become weak and sparse, as the growth of turfgrasses is limited by the low light intensity and energy reserves.
The potential for successfully establishing and maintaining turf under a single, solitary tree is usually much greater than within a “forest” of trees with a closed canopy. Individual trees in a landscape often create “moving” shade, allowing turfgrasses an opportunity to intercept direct light at some point each day.
Annual interseeding may be necessary to maintain turfgrass stand density in shady locations. Seeding cool-season turfgrasses under deciduous trees in late summer (from mid-August to mid-September) provides the longest exposure to direct light before the tree’s foliage returns the next year.

Turfgrass Growth Habit

Turfgrasses vary in their growth habit. Sod-forming turfgrasses produce stems above and below ground level. Above-ground stems, referred to as stolons, have nodes from which new plants develop. Below-ground stems, called rhizomes, are also capable of producing new plants. Stolons and rhizomes are very important because they store energy and can fill areas void of vegetation resulting from high- or low-temperature extremes or from disease or insect damage.
Turfgrasses with no stolons or rhizomes have a bunch-type growth habit. These species move laterally by way of segmented stems or tillers. The diameter of individual plants increases as the turfgrass matures and more tillers are formed. (see Figure 2.) Occasional interseeding may be needed to maintain the stand density of turfgrasses with a bunch-type growth habit.

Perennial Warm-season Turfgrasses

Bermudagrass

Bermudagrass is a very aggressive, sod-forming species with both rhizomes and stolons. It is tolerant of drought and traffic, and it grows best in fertile, well-drained soils. Several varieties of bermudagrass, in addition to the standard Arizona Common variety, can be established from seed, including ‘Arden 15’, ‘Blackjack’, ‘Casino Royale’, ‘Rio’, ‘Monaco, ‘Mirage 2’, and ‘Yukon’. However, many excellent hybrid bermudagrass varieties do not produce viable seed and can only be vegetatively established from sod, sprigs (stem portions), or plugs. These include ‘Celebration’, ‘TifTuf’, ‘Latitude 36’, ‘NorthBridge’, ‘Iron Cutter’, ‘TifGrand’, and ‘Tifway’ (Tifton 419). Bermudagrasses are generally intolerant of shade.

With the introduction of cold-tolerant varieties such as ‘Latitude 36’, ‘Northbridge’, ‘Rio’, and ‘Yukon’, bermudagrass use has expanded from southwest into northeast Tennessee. Bermudagrass can be overseeded with perennial ryegrass (Lolium perenne) to provide green color while bermudagrass is dormant. However, this rapidly growing, cool-season, bunch-type species competes for nutrients, water, and light as bermudagrass resumes growth in the spring.

Zoysiagrass

Zoysiagrass, like bermudagrass, is a sod-forming species producing both rhizomes and stolons. It is drought tolerant and slightly more shade tolerant than bermudagrass, and it generally grows much more slowly. Several Zoysia japonica varieties, including ‘Meyer’ and ‘Palisades’ (see page 10-10) are more cold tolerant than bermudagrass. These varieties must be vegetatively established via sod, plugs, or sprigs. However, the Zoysia japonica varieties ‘Zenith’ and ‘Compadre’ can be established from seed. Zoysia matrella varieties such as ‘Cavalier’, ‘Zeon’, ‘Royal’, ‘Zorro’, and ‘Stadium’ have a finer texture and are often denser than the Zoysia japonica varieties. There are a growing number of interspecific hybrids including ‘Innovation’ (Z. japonica x Z. matrella) which offer characteristics of both species including finer texture and improved cold tolerance. Because of the slow rate of growth and the high density of zoysiagrass, perennial ryegrass overseeding for winter color is not recommended.

Centipedegrass

This slow growing, sod-forming species spreads laterally by way of stolons and has no rhizomes. Centipedegrass produces a medium-textured turf light green in color (resembling that of a Granny Smith apple). The species grows best in full sun, has fair shade tolerance, and is adapted to infertile soils. Centipedegrass does not grow well in alkaline soils or in sandy soils containing large populations of plant parasitic nematodes.
Maintenance requirements are relatively low compared to bermudagrass. The stem color of ‘Common’ centipedegrass may be green, red, or yellow, with red-stemmed strains usually being more tolerant of low temperatures. Common centipedegrass seed marketed in Tennessee usually yields a mixture of red- and yellow-stemmed plants. The limited low-temperature hardiness of common centipedegrass has restricted its use in home lawns in Tennessee. The improved ‘TifBlair’ variety (see page 10-10) has much better cold tolerance than Common centipedegrass, and consequently this seeded variety has been used in various locations in the state.

Perennial Cool-season Turfgrasses

Tall Fescue

With a bunch-type growth habit, tall fescue is moderately drought and shade tolerant, and it is adapted to a wide range of soil conditions. Two varieties, ‘Kentucky 31’ (‘KY 31’) and ‘Alta’, were released in the early 1940s. KY 31 was found growing in a pasture on the farm of W. M. Suiter in the mountains of eastern Kentucky and was known to have been there before 1890. After lengthy testing initiated by Dr. E. N. Fergus of the University of Kentucky, who first saw the pasture in 1931, the variety was released for sale in 1943. Although other turf-type tall fescue cultivars are now recommended for use in home lawns, KY 31 is still used as a forage species and planted for roadside erosion control and turf.

Alta was selected based on winter hardiness, persistence, and its ability to remain green during summer drought in western Oregon. This variety was released cooperatively by the Oregon Agricultural Experiment Station and the U.S. Department of Agriculture. Breeding efforts have resulted in the development of new varieties with leaf textures comparable to Kentucky bluegrass and also having rhizomes. These improved, turf-type tall fescues often outperform KY 31 in Tennessee lawns. Turf-type tall fescue seed is often sold in blends with multiple varieties. Introducing multiple varieties may improve overall resilience of a stand, as unique varieties may offer unique stress tolerance at a given site. It is also not unusual that fine fescues or Kentucky bluegrass may be combined with tall fescue in both seed and sod to enhance overall resilience of a stand to tolerate stresses such as shade, traffic, or heat.

Top 10 Low-Input Tall Fescue Varieties for Tennessee

1. Firecracker GLS
2. Grande 3
3. SuperSonic
4. Xanadu (JT-268)
5. Bonfire (JS DTT)
6. Reflection
7. Lifeguard
8. Saltillo
9. 2nd Millennium
10. Avenger III

Kentucky Bluegrass

Although some companies market seed mixtures and sod of Kentucky bluegrass plus improved, turf-type tall fescue(s) for lawns in full sun and light shade, the management of a high quality monostand of Kentucky bluegrass (shown on page 10-12) most often requires routine irrigation to supplement the state’s natural rainfall. This medium- to high-density, sod-forming species produces rhizomes but no stolons. Two disadvantages are a fairly shallow root system under mowed conditions and a relatively high demand for water.
Kentucky bluegrass is less drought tolerant than tall fescue, and it usually grows best in fertile soils. In summer, plants exposed to extended periods of heat and drought often become dormant. Those that survive summer dormancy recover from rhizomes and nodes on crowns (see Figure 3) once air temperatures drop and it rains or as irrigation is resumed.
In an effort to develop bluegrasses with improved heat and drought tolerance, breeders have successfully crossed Kentucky bluegrass with Texas bluegrass (Poa arachnifera), a species native to Texas. Dr. James Read of Texas A&M University released the first commercially available hybrid bluegrass variety ‘Reveille’. Since then, several more hybrid bluegrasses have been released including ‘Bandera’, ‘Dura Blue’, ‘Fahrenheit 90’, ‘Fire and Ice’, ‘Longhorn’, ’Solar Green’, ‘Spitfire’, ‘Thermal Blue’, and ‘Thermal Blue Blaze’. Although they are actually hybrids, these varieties are usually marketed as heat-tolerant (HT) Kentucky bluegrass.

Fineleaf Fescues

The varieties classified as fineleaf fescues include chewing’s (Festuca rubra subp. commutata), hard (Festuca longifolia or duriuscula), slender creeping red (Festuca rubra subp. litoralis), strong creeping red (Festuca rubra subp. rubra), and sheep (Festuca ovina), or blue, fescue. As their name implies, these species have narrow and often needlelike leaves. (see page 10-14.) They generally grow slowly and require less nitrogen (N) than other cool-season turfgrasses.
Fineleaf fescues have good-to-excellent shade tolerance and as a result, seed of three of the five turfgrasses (strong creeping red, chewing’s, and hard fescues) is often combined and sold as a shade mixture. However, a general lack of heat tolerance among the species and subspecies limits their persistence and use in shaded lawns in much of Tennessee. Hard fescue is usually more tolerant of high temperatures than either chewing’s or strong creeping red fescue. Neither chewing’s nor hard fescues produce stolons or rhizomes. Sheep and hard fescues are sometimes planted along with native grasses and wildflowers in meadows and naturalized areas.

Find Your Ideal Variety

A-List Turf (a-listturf.org) and the Turfgrass Water Conservation Alliance (tgwca.org) conduct ongoing turfgrass variety research and publish their recommendations on their websites. These resources may be helpful as you select a variety for your lawn.

Establishing Turfgrasses

Timing

The preferred time to establish a lawn is influenced by the turfgrass species and the planting method. Air temperatures that cycle between 59° and 82°F favor the germination of cool-season turfgrass seeds. Since Kentucky bluegrass and the fescues grow best when air temperatures are cool, late August to mid-October is an excellent time to plant seed. Planting seeds of cool-season turfgrasses in late winter or early spring often results in poorly developed seedlings that may not be capable of surviving hot, dry weather in summer.
Warm-season turfgrass seeds germinate best at air temperatures from 68° to 95°F. Seed, plugs, or sprigs of bermudagrass, centipedegrass, or zoysiagrass should be planted between May 1 and June 30 to allow plants adequate time to mature before fall frost.
In Tennessee, sod is often installed throughout the year as long as the planting bed is not frozen or the weather is not extremely unfavorable. Many producers will not harvest or ship cool-season turfgrass sod during hot, dry weather. Although it is not uncommon to install dormant bermudagrass or zoysiagrass sod, several weeks or months may be required before a newly sodded lawn can withstand traffic.

The Right Timing

For best results, bermudagrass, zoysiagrass, and centipedegrass seed should be planted in late spring or early summer and no later than June 30. Warm summer temperatures promote the growth of seedlings well before the first frost in the fall.
Kentucky bluegrass, tall fescue, and fineleaf fescue seed should be planted in late summer or early fall and no later than mid-October. This timing should allow seedlings time to mature before experiencing heat stress the following summer.

Preparing to Plant

When properly prepared, the planting surface or seedbed should be firm and fertile. It should be free of weeds and stones or debris that can block turfgrass roots and restrict water infiltration or percolation. The following 10-step plan will achieve these objectives:

1. Submit a soil sample for testing six weeks before the intended planting date. A soil sample can be taken using a trowel, garden spade, or soil tube. Collect several small samples (for example, one or two samples per thousand square feet) each to a consistent depth of 4-6 inches if possible. Discard vegetative material before placing the samples in a clean container to dry. Thoroughly break up and mix the dry samples before transferring 1/2 pint of soil (the representative sample) to the soil sample box. Consider submitting at least one representative soil sample from the front yard and a second from the back yard.
2. Stockpile existing, on-site topsoil before soil contouring and major excavation begins. Topsoil usually contains more organic matter and beneficial microorganisms than subsoil, providing plants a better rooting environment. Buried electrical, gas, cable, and water lines should be identified and flagged before any soil is moved. Dozers and graders are often equipped with laser technology allowing the equipment operator to create precise contours.
3. Establish the “rough” grade. Setting the proper initial base or rough grade will help prevent water damage to the home or its foundation and speed the flow of excess surface water across the landscape.
4. Uniformly redistribute topsoil. The topsoil depth should be no higher or lower in swales or depressions than on knolls or hills.
5. Once topsoil is in place and at final grade, subsurface drainage and irrigation systems (if desired) can be installed. Drainage pipe is usually placed at least 6 inches below the soil surface. Sprinkler irrigation mainlines are often much deeper. They should be located well below the frost line and normal tillage depth (for example, 12 to 18 inches).
6. Remove stones more than 2 inches in diameter and debris that would interfere with turfgrass rooting or restrict the movement of water into and through the soil.
7. Control weeds. A broad-spectrum, systemic herbicide such as glyphosate (for example, Glyphosate-4 Plus, Gordon’s Pronto Big N’ Tuf 41% Glyphosate Weed & Grass Killer, FarmWorks 41% Glyphosate Plus, or 41% Glyphosate Plus Grass & Weed Killer) can be applied to control many species of emerged annual and perennial broadleaf and grassy weeds up to seven days before planting turf. For more aggressive weed species, multiple applications may be required before planting.
8. Broadcast fertilizer and lime according to soil test recommendations.
9. Cultivate (for example, roto-till or disk to a 4- to 6-inch depth) to mix fertilizer and lime with soil. Mature compost can also be incorporated (for example, 10 to 15 percent by volume) along with fertilizer and lime. The compost will increase the soil organic matter content, supply essential nutrients, and increase the water-holding capacity of the soil. Avoid using fresh or partially decomposed composts. These materials often contain very high levels of soluble salts that could kill germinating seeds and developing seedlings.
10. Smooth and firm the soil surface. Hand raking and a water-ballast roller work well in small areas. A large, tractor-drawn cultipacker, heavy steel drag mat, or plank drag are effective when preparing to plant large areas. The planting bed will require further rolling or dragging if footprints are deeper than 1 inch.

The Right Seedbed

The planting or seedbed should be firm, fertile, and free of stones and debris that will interfere with turfgrass rooting and the infiltration and percolation of water. Footprints should be no deeper than 1 inch, and stones more than 2 inches in diameter and within 4 inches of the soil surface should be removed before planting.

Planting Methods

Turfgrasses may be established in several ways. Many varieties produce viable seeds that can be harvested and planted to produce new turf stands. However, several very popular turfgrass varieties are sterile hybrids and must be vegetatively established. Some varieties of bermudagrass and zoysiagrass produce no seeds and are commonly established from sprigs (segments of stolons and rhizomes capable of producing new plants) or from sod plugs. Both non-seed-producing and seed-producing turfgrass varieties are marketed as sod.

Seeding

Because of differences in seed size, the recommended seeding rate varies among turfgrass species. (see Table 2.) The amount of time required for seeds to germinate also depends on the species.
On average, 1 pound of tall fescue seed contains about 250,000 seeds, while 1 pound of Kentucky bluegrass seed typically contains more than 2,100,000 seeds. A seeding rate of 5 pounds of tall fescue seed per thousand square feet usually delivers about 9 seeds per square inch. In comparison, the recommended seeding rate of 1 to 1½ pounds of Kentucky bluegrass seed per thousand square feet delivers about 14 to 21 seeds per square inch.
Seeds can be uniformly broadcast over a relatively small planting bed by hand or by using an “over-the-shoulder” seeder-spreader. Push-type, rotary, and drop spreaders are also engineered to broadcast turfgrass seeds. Larger planting beds are often seeded using a tractor-drawn seed drill, cultipacker planter, or motorized, walk-behind slit-seeder, as shown on page 10-18. To improve uniformity of seed distribution, the planting bed can be seeded in two or more directions. Hydraulic planters or hydroseeders can also be used to broadcast seeds (by hydroseeding) or a combination of seeds, mulch, and tackifier (by hydromulching) in water. A tackifier is an additive that helps seeds adhere to the hydromulch and soil.

Seed Blends and Mixtures

A seed blend contains two or more compatible varieties of the same species, as illustrated on page 10-18. Blending varieties can be advantageous. For example, one variety in a three-variety blend may have superior disease tolerance, another may have excellent drought tolerance, and the third may be well adapted to shady areas of a landscape. In mature turfs, it is usually very difficult to distinguish between varieties that are similar in leaf texture, stand density, and color.
A seed mixture contains two or more species of turfgrass. Seeds of two or more species are usually mixed in an effort to ensure total groundcover when the climate (wind, air temperature, relative humidity, and other factors) and soils (level of compaction, fertility, internal drainage, topsoil depth, and so on) vary across a landscape. Although mixing seeds of several species may improve insect and disease resistance, shade tolerance, and wear resistance, mature turfs established from a seed mixture may eventually appear patchy because they consist of isolated areas of individual, contrasting species.
Mixing annual or perennial ryegrasses, two short-lived species, with fescues and bluegrasses is usually discouraged partly because of the potential for ryegrasses to quickly dominate the stand. Ryegrass seeds germinate fast and seedlings grow rapidly compared to those of Kentucky bluegrass and tall fescue. However, mixing compatible varieties of chewing’s fescue with hard and strong creeping red fescues can be helpful when establishing a shaded turf from seed.
The seed count of each individual species per pound should be considered when selecting components of a seed mixture. Turfgrasses in a mixture are listed by weight. For example, a one-pound mixture of 80 percent Kentucky bluegrass, 10 percent strong creeping red fescue, and 10 percent perennial ryegrass by weight contains about 95.4 percent Kentucky bluegrass seeds (about 1,760,000 seeds), 3.3 percent strong creeping red fescue seeds (about 61,500 seeds) and 1.3 percent perennial ryegrass seeds (about 23,000 seeds) by count. Seeds may be coated with lime, fertilizer, fungicide, or a water-absorbing polymer. Coatings can improve the germination of seeds and speed the growth of seedlings while protecting them from fungal pathogens. However, coating seeds increases the weight of each seed “unit” and decreases the total seed count per pound.

The Seed Label

The label on a container of seed provides valuable information about the quality of the seed inside. The label of every container of turfgrass seed sold, distributed, transported, and offered for sale in Tennessee must contain the following information:

• Name of each turfgrass species and variety found in excess of 5 percent of the whole and the percentage by weight of each in the order of its predominance
• Lot number or other lot identification
• Net weight
• Origin
• Percentage by weight of inert matter
• Other crop seeds (the percentage by weight of varieties other than those listed on the label)
• Percentage by weight of all weed seeds
• Germination percentage (exclusive of the germination of hard seeds), percentage of hard seeds, and the calendar month and year of the test for seeds of each named turfgrass
• Name and number per pound of each kind of restricted, noxious weed seed
• Name and address of the company or person labeling, selling, or offering the seed lot for sale.

The seed germination test is valid for nine months.
Seed may also be guaranteed true to type, or certified, from a genetic standpoint. Blue-tag certified seed has been tested according to procedures established by the Association of Official Seed Certifying Agencies (AOSCA) and must meet stringent certification standards for genetic purity and identity.

Comparing Seed Costs

The retail price per pound of turfgrass seed is influenced by turfgrass species and variety and by seed germination rate and purity. A calculation to determine the percentage of pure live seed (PLS), where PLS (%) = [seed purity (%) × germination (%)] ÷ 100, makes it possible to compare the price of two or more seed lots and identify the best value.
As an example, let’s assume that a turf-type tall fescue variety ‘Speedway’ has a germination rate of 90% and a purity of 99.58% (100% – 0.09% other crop − 0.27% inert matter – 0.06% weed seed = 99.58% purity).
The percentage of pure live seed of this seed lot is calculated as follows:
PLS (%) = [99.58 (% purity) × 90 (% germination)] ÷ 100 = 8872.2 ÷ 100 = 88.72%
If the retail price per pound is $1.40, the retail price per pound of pure live seed = $1.40 ÷ 0.8872 = $1.58
Similar calculations can be run on other products to determine which is the best value.

Sodding

Turfgrass sod can be transplanted almost any time of year as long as the soil is not frozen and water can be provided by irrigating as needed. Although bermudagrass and zoysiagrass sod can be installed during winter dormancy, it may take several months for plants to root into the soil below. Many producers will not harvest and ship Kentucky bluegrass, tall fescue, or tall fescue + Kentucky bluegrass sod in the summer during extremely hot, dry weather.
Sod is harvested in large rolls 24, 30, or 48 inches wide and up to 100 feet long or in smaller pads — for example, 16 inches wide by 24 inches or more long that are stacked or rolled on a pallet, as shown on page 10-20. Several equipment manufacturers sell sod harvesting machines that simultaneously cut two large rolls, each 21 or 24 inches wide.
One pallet of sod usually contains about 50 square yards of sod pads and weighs about 2,000 pounds, or 1 ton. From 3/8 to 5/8 inch of soil is usually shipped along with turfgrass plants. Sod pads may be reinforced with biodegradable netting installed at the sod production site immediately after seeding, as shown on page 10-21.
Large rolls of sod are usually installed using tractors with flotation tires or vehicles with rubber tracks and a load capacity of 2,500 pounds or more. Sod pads should be installed in rows in a checkerboard pattern as shown on page 10-21 to limit the formation of long lines of exposed soil between pads. Each side of an individual sod pad should touch the side of another sod pad. Pads should not be stretched or overlapped as sod is transplanted. Biodegradable stakes can be used to secure sod to sloping soils.
Sod is inspected by Tennessee Department of Agriculture professionals and certified free of noxious pests before being shipped to the consumer. Inspectors employed by the Tennessee Crop Improvement Association certify that sod is genetically “true to type.”
Plugging
Turfgrasses capable of producing stolons and rhizomes can be plugged, as shown on page 10-21. Several factors, including turfgrass species, planting date, plug diameter and spacing, soil fertility and moisture levels, and the amount of weed competition affect how much time it takes for plants to fill in the voids among plugs. When bermudagrass plugs 4 inches in diameter are planted from mid-May through mid-June at 9 inches on center and provided with routine fertilization, weed control, and irrigation, the bermudagrass ground coverage often reaches 90 percent or more by the first fall frost.
Although the lateral rate of growth of some varieties of zoysiagrass (for example, the Zoysia japonica varieties El Toro and Palisades) is faster than others (for example, the Zoysia matrella varieties Cavalier, Royal, Zeon, and Zorro), two full growing seasons may be needed for complete ground coverage when 4-inch plugs are planted on 9-inch centers. The limited rate of growth of zoysiagrass stolons and rhizomes increases the amount of time from planting to harvest of sod compared to that of bermudagrass, resulting in a higher retail value for zoysiagrass than bermudagrass sod.
Plugs may be available for purchase at retail garden centers or via the Internet. Plugs can also be cut from sod using a machete or hand-held plugger, as shown on page 10-22. About 80 plugs 4 inches in diameter or width can be cut from 1 square yard of sod. Sixteen plugs are needed per square yard of planting bed surface when using 4-inch plugs on 9-inch centers.
For plugs, the planting bed should be moist but not saturated. Plugs should be installed so that the soil surface of each plug is level with that of the planting bed. Each plug should be pressed from above or rolled after planting to ensure that the soil at the base of the plug is in direct content with the soil below.

Stolonizing, Sprigging, and Hydrosprigging

Sprigs are harvested at the sod farm and sold by the bushel. One industry-standard bushel is equivalent to a volume of 0.4 cubic foot. Generally, 1 square yard of sod yields about one industry-standard bushel of sprigs. Small areas can be planted by broadcasting (stolonizing) sprigs over the soil surface by hand, as shown on page 10-23, or planting them 4 inches or more apart in furrows 1 to 2 inches deep (by sprigging or row planting). Tractor-drawn stolonizers or row planters are often used to plant larger areas. Depending on engineering design, tractor-drawn planters uniformly broadcast sprigs over the planting bed and “punch” them into the soil surface or plant them in rows 4 inches or more wide. The spacing among individual sprigs depends on planting rate (for example, from 2 to 10 or more bushels per thousand square feet) and row width. The amount of time from planting to total ground coverage most often decreases as the spacing of sprigs between and within rows narrows.
A hydraulic planter can also be used to broadcast sprigs via a process called hydrosprigging. Hydrosprigging is especially effective when the goal is to plant sprigs with very little disruption of the soil surface.

Care After Planting

Mulching a newly seeded planting bed with straw at the rate of 50 pounds of straw per thousand square feet, as shown on page 10-24, or installing an excelsior (for example, aspen fiber) or straw blanket (see page 10-24) can help preserve soil moisture, control erosion, and suppress weeds. Poor quality straw can also introduce weeds.
Seeds require water to germinate, and turfgrass plants require water to survive. New plantings may require light irrigation for several weeks — for example 1/8 to ¼ inch daily, equivalent to about 150 gallons per thousand square feet per day. As plants grow and roots reach a greater soil depth, more water can be applied less often — for example, ½ inch or about 300 gallons per thousand square feet every three days.
Begin mowing upright, bunch-type species such as tall, chewing’s, and hard fescues at a 2-inch cutting height when plants reach an average height of 3 inches. (see page 10-24). Begin mowing sod-forming species, including hybrid bermudagrass and zoysiagrass, at a cutting height of 1½ inches when plants reach an average height of 2¼ inches.
The application of ½ pound of N per thousand square feet three to five weeks after planting sod, plugs, or sprigs, or after seedlings emerge from the soil, will support continued plant growth. Nitrogen should not be applied if plants are stressed by high or low temperatures.
It is seldom necessary to remove straw mulch or excelsior blankets after seeding. If high winds or heavy rainfall cause windrows or heavy accumulations of mulch, spread the mulch as evenly as possible. Too many tree leaves lying on the turf surface can also block light and weaken plants. Routine mowing, raking, or vacuuming may be needed.
The turf should be routinely scouted for wilting, discoloration, and defoliation. Seedlings with poorly developed roots often suffer more severe injury from fungal pathogens than mature turfgrass plants. For example, tall fescue seedlings are far more prone to large brown patch (Rhizoctonia solani), Pythium blight (Pythium aphanidermatum and Pythium ultimum), and gray leaf spot (Pyricularia grisea) than heavily tillered, well-rooted plants. The activity of white grubs, the larvae of scarab beetles such as the green June beetle (Cotinis nitida), and Japanese beetle (Popillia japonica) can be monitored by looking below the soil surface both within and just beneath the roots. When fall armyworm (Spodoptera frugiperda) larvae occur in large numbers, they defoliate turfgrasses and cause extensive damage very quickly.
Annual and perennial broadleaf and grassy weeds can compete with developing turfgrasses for essential nutrients, light, and water. Some herbicides can be applied immediately before or after certain turfgrasses are planted. At the time this chapter was written, the following information was presented on the Drive XLR8 and the Gordon’s Trimec Lawn Weed Killer labels. The use of the herbicide Drive XLR8 (with active ingredient quinclorac) before or after seeding or overseeding will not interfere with the seed germination or seedling growth of Common bermudagrass, Kentucky bluegrass, perennial ryegrass, tall fescue, or zoysiagrass. The herbicide can also be applied before, during, or after sprigging Common or hybrid bermudagrasses and zoysiagrass. Drive XLR8 is not labelled for use on centipedegrass. The herbicide Gordon’s Trimec Lawn Weed Killer (with active ingredients 2,4-D, mecoprop, and dicamba) should not be applied to new lawns until the bermudagrass, centipedegrass, fescue, Kentucky bluegrass, perennial ryegrass, or zoysiagrass plants have reached an average height of 2 inches.
Common turfgrass diseases, insects, and weeds will be discussed in more detail in the Turfgrass Pests Section of this chapter.

Managing Turf

In addition to being mowed, turf in a home landscape can be fertilized, irrigated, dethatched, aerated, topdressed, and rolled. The turf should also be routinely monitored for turfgrass diseases, insect activity, and weeds.

Mowing

Because of their ability to produce new cells, buds, leaves, tillers, and stolons at or just above the soil surface, turfgrasses tolerate repeated defoliation by mowing. The recommended cutting height is influenced by the species being managed and the weather, as shown in Table 3. For example, turfgrasses with stolons and rhizomes such as bermudagrass, centipedegrass, creeping red fescue, Kentucky bluegrass, and zoysiagrass can be mowed lower than bunch-type turfgrasses such as chewing’s fescue, hard and tall fescues, and perennial ryegrass.
A turf should be mowed when the average plant height is 1½ times that of the cutting height. This timing ensures that no more than one-third of the aerial shoots will be removed. Short clippings generally decompose rapidly and do not contribute significantly to the thatch layer. Because of the N they contain in relation to carbon (C), clippings collected rather than returned to the turf could also serve as greens when added to a compost pile.
Regardless of the type of mower being used, the edges of blades and bedknives should be kept sharp. Turfgrass leaves torn by a dull blade, as shown on page 10-26, provide fungal pathogens an opportunity to move directly inside the plant. Mower blades and reel mower bedknives usually require sharpening at least once each year. Changing the direction of mowing from one mowing to the next encourages turfgrass plants to grow upright, limiting the formation of grain and more uniformly distributing compaction of the soil resulting from the passage of the mower wheels.

Essential Nutrients

As discussed in Chapter 5, “Soil Science and Plant Nutrition,” 18 nutrients have been identified as essential for turfgrass growth and reproduction. Three of these — C, hydrogen (H), and oxygen (O) — are nonminerals making up more than 90 percent of dry turfgrass tissue, as shown in Table 4. Thanks to chlorophyll within chloroplasts in the cells of leaves and aerial stems (shoots), the light striking exposed plant surfaces is converted to compounds that provide energy for growth or can be stored for use at a later date. Atmospheric carbon dioxide provides turfgrasses with C and O. Turfgrasses receive both H and O from water as it enters root hairs and moves throughout the plant.

The remaining 15 essential nutrients are minerals. In order for a nutrient to be considered an essential nutrient

1. a plant must be unable to complete its life cycle when the nutrient is not available,
2. the function of the nutrient cannot be replaceable by another nutrient, and
3. the nutrient must be part of an essential plant constituent or directly involved in photosynthesis, respiration, or the production and breakdown of organic compounds within the plant (metabolism).

Although they are equally important, essential mineral nutrients are further classified as primary macronutrients, secondary macronutrients, and micronutrients according to the amount of each found in turfgrass tissue. As their name implies, macronutrients are required in relatively large amounts (1,000 parts per million or more in plant tissue) and micronutrients in very small amounts (often less than 100 parts per million in plant tissue).

Primary Macronutrients

Nitrogen

Turfgrasses require N to produce chlorophyll, which is critical for photosynthesis. As a result, older leaves of turfgrasses deficient in N usually turn light green to pale yellow as the nutrient is mobilized and moves to growing points and other “high demand” areas of the plant. This condition is referred to as foliar chlorosis. Because actively growing turfgrasses perform best with consistent supplies of N, fertilizers containing extended-release nitrogen are a popular choice for turf applications.

Phosphorus

Often referred to as the energy nutrient, phosphorus (P) helps turfgrasses produce and maintain healthy roots. Compared to N and potassium (K), P is used in relatively small amounts. However, a turf “starter” fertilizer often contains more P2O5 (phosphate) than N.

Potassium

Although K is not a component of amino acids, carbohydrates, proteins, or sugars, turfgrasses with adequate K are often better able to overcome extended periods of drought and cold temperature stresses than those low or deficient in this element. High concentrations of ammoniacal nitrogen (NH4+) or low concentrations of nitrate (NO3-) in soil can severely limit the uptake of K by turfgrasses.
The amount of each primary essential macronutrient found in turfgrass tissue in descending order is N > K > P.

Secondary Macronutrients

Calcium

Calcium (Ca) deficiencies in turfgrasses are uncommon when the soil is slightly acidic — for example, at a pH from 6.0 to 6.5. In the rare event that the addition of Ca is recommended for turfgrasses growing in a soil with an optimum pH, granular gypsum (CaSO4) can be applied rather than lime, which would raise the soil pH. An application of this “neutral” salt will neither lower nor raise the soil pH. The level of Ca in turfgrass tissue is usually much higher than that of magnesium (Mg) or sulfur (S).

Magnesium

Because Mg is a component of chlorophyll and, like N, is required for photosynthesis, turfgrasses low or deficient in the nutrient also have yellow leaves. Unlike the oldest leaves of turfgrasses deficient in N that are totally chlorotic, the veins of leaves of turfgrasses low or deficient in Mg often remain green. This condition is referred to as interveinal chlorosis.

Sulfur

Sulfur is required by turfgrasses to produce several amino acids and, as a result, several proteins. Sulfur applications to turf may also reduce the severity of certain fungal diseases including dollar spot, Fusarium patch, and Ophiobolus patch. Granular S can be broadcast over turf to lower the pH of highly alkaline soils.

Micronutrients

Because turfgrasses require only minute amounts of the nine essential micronutrients, when turf is maintained in slightly acidic, mineral soils throughout Tennessee it rarely benefits from an application of micronutrients. However, one or more micronutrient applications may be necessary when turfgrasses are growing in strongly acidic or alkaline soils and micronutrients are no longer in a plant-available form. Turf growing in sandy soils prone to nutrient leaching, or in soils containing high levels of organic matter, may respond favorably to micronutrient application. However, to reduce the potential for creating micronutrient toxicity, applications should be based on soil test results or plant analysis.

Boron

Turfgrasses are unable to move sugars produced by way of photosynthesis from one area to another without adequate boron (B). Boron also enables plant cells to differentiate into leaves and stems. Growing points of turfgrasses deficient in boron may develop yellow streaks, and leaves are often stunted. Boron is absorbed from soil as borate (BO33-), a negatively charged ion.

Chlorine

In addition to supporting photosynthesis, chlorine (Cl) is believed to be involved in the balance of nutrients inside plant cells. Leaves of turfgrasses deficient in Cl first wilt and become chlorotic before dying.

Cobalt

A micronutrient recently determined to be essential, cobalt (Co) is important for the fixation of nitrogen in plants.

Copper

Several enzymes in turfgrasses contain copper (Cu). Since Cu can bind with organic compounds, deficiencies of the micronutrient have been observed in turfgrasses growing in soils high in organic matter. Turfgrasses growing in sandy or alkaline soils and in soils with high N, P, iron (Fe), manganese, zinc, or pH levels may also be low or deficient in Cu. An application of too much Cu can cause an Fe deficiency in turfgrasses.

Iron

Iron is necessary for chlorophyll formation and photosynthesis. Deficiencies of this micronutrient cause chlorosis of young leaves. The tissue between veins of these leaves usually becomes yellow as Fe becomes more limited. Turf areas may be sprayed with a solution containing Fe to enhance green color without causing excessively rapid leaf growth.

Manganese

Manganese, like Fe, is necessary for the formation of chlorophyll. The micronutrient is also involved in the function of several plant enzyme systems. Leaves of turfgrasses lacking Mn often have gray or tan spots. Too much Fe in turfgrass tissue may result in low or deficient levels of Mn. Long periods of dry, warm weather can reduce Mn availability in soil.

Molybdenum

Molybdenum (Mo) is involved in the formation of proteins and the use of N and S by turfgrasses. This micronutrient also affects the production of pollen. The concentration of Mo in turfgrasses is highest in the leaf blade, and the micronutrient tends to accumulate as plants mature. Leaves of turfgrasses deficient in Mo are often twisted, and their edges may appear scorched.

Nickel

Most recently classified as an essential micronutrient, nickel (Ni) is a component of an enzyme and is involved in the development of seeds.

Zinc

Several enzymes involved in the production of proteins and carbohydrates contain Zn. Zinc deficiencies have occurred more often in turfgrasses in shade, in alkaline or acidic soils, and during cool, wet weather.

Soil Testing

The major goal of a soil testing lab for each sample being tested is to accurately predict the soil pH and the amount of each nutrient that will be available to turfgrasses. After drying, grinding, and weighing the sample, a solution is used to saturate and extract nutrients from the soil sample. The soil extract is then analyzed by a laboratory instrument (for example, an automated plasma atomic emission spectrometer) to determine the amount of each nutrient present. An automated pH analyzer is often used to determine the pH of the water in the soil (WpH).

Soil pH

The pH of a soil directly affects the solubility of the essential mineral nutrients it contains and their availability to plants. Slightly acidic soils (with a pH range between 6.0 and 6.5) are preferred when managing turfgrasses in native soils.
Soil pH decreases with increasing soil acidity. In strongly acidic soils, several nutrients, including P, become less available to plants because they react with Fe and aluminum (Al) to form precipitates and are thus not in a form that plants can use. The amount of lime needed to neutralize acids in a soil and raise the pH depends on the ability of the soil to resist or buffer against a change in pH. Clay soils have a greater buffering capacity than sandy soils. If lime is recommended, the buffer pH (BpH) will appear on the soil test report along with the WpH. The BpH is a value generated in the laboratory in order to develop specific lime recommendations.
As the pH of a soil increases above 7.0, a lack of Mn may limit the rate of turfgrass growth. Similarly, less Fe, Cu, and Zn are available for plant uptake as soil becomes more alkaline. However, as the soil pH rises above 6.5, P and Mo may become more available to plants. The application of S may be recommended to lower soil pH if needed.

Lime and Liming

Lime is available for turf applications in both pulverized and granular forms, and it can be purchased in bulk quantities or in bags. Granular or pelletized lime with uniform particles is usually preferred when applying lime using a walk-behind or three-point-hitch rotary spreader. Calcitic lime is manufactured by grinding rock containing large amounts of calcium carbonate, while rock with a combination of both calcium and magnesium carbonates is used to produce dolomitic limestone. Dolomitic limestone often consists of about 50 percent calcium carbonate and about 40 percent magnesium carbonate. Dolomitic limestone is preferred when both the soil pH and the available magnesium level in the soil are low. Generally, no more than 50 pounds of lime per thousand square feet is recommended per application to established turf.

Plant-available Nutrients

Each nutrient tested at the University of Tennessee Soil, Plant, and Pest Center is reported in pounds per acre (lb/A) and assigned a soil test rating. Some soil testing labs report nutrients tested in parts per million (ppm) rather than pounds per acre. For a 6-inch soil sample, parts per million can be converted to pounds per acre by multiplying by two.
Soil test ratings for P and K are reported as low (L), medium (M), high (H), or very high (V), where low (L) indicates that, in most cases, turfgrasses will respond to an application of that nutrient and that if the nutrient is not applied, deficiency symptoms may occur. Medium (M) indicates that turfgrasses may or may not respond to an application of the nutrient and that deficiency symptoms are not likely. High (H) indicates that any amount of the nutrient recommended is intended to maintain the existing soil test level; and very high (V) indicates that an application of the nutrient is not recommended because further additions may create nutrient imbalances. Ratings for secondary macronutrients and micronutrients are reported as either sufficient (S) or deficient (D).

The Soil Test Report

An example of a University of Tennessee Soil Test Report is shown on the adjacent page. The pH of the soil tested is 5.8, and a total of 100 pounds of lime per thousand square feet is recommended to raise the soil pH to 6.5. However, since no more than 50 pounds of lime should be broadcast over turf at one time, an initial lime application of 50 pounds per thousand square feet should be followed by a second lime application of 50 pounds per thousand square feet several months later.
A Mehlich 1 extractant solution was used to estimate the amounts of P, K, Ca, Mg, Zn, Fe, Mn, sodium (Na), and B that are reported in pounds per acre (lb/A). Procedures were not performed to determine the amounts of sulfate (SO4), nitrate (NO3), C, and organic matter nor the level of soluble salts in the soil. This report notes that the soil is high in P at 44 pounds per acre, and low in K at 38 pounds per acre. It has sufficient amounts of Ca at 1,179 pounds per acre, Mg at 90 pounds per acre, Zn at 13.3 pounds per acre, Fe at 19 pounds per acre, and Mn at 14 pounds per acre. The soil also contains 0.6 pound of B per acre and 7 pounds of Na per acre. An explanation of a similar University of Tennessee Soil Test Report is presented in the supplemental materials online.

Developing a Fertilization Program Based on Soil Test Results

Based on the soil test results, one of three levels of turf maintenance must be chosen before an appropriate fertilization plan can be implemented. A turf maintained at the lowest intensity level most often requires less frequent mowing than at medium or high intensity levels. However, at times, the turf may contain more weeds and may not provide the desired level of overall turfgrass quality. Generally, the highest turf maintenance intensity level is most successful if an irrigation system is available and the automatic controller is properly set.
The total amount of N and the number of fertilizer applications recommended annually for cool-season turfgrasses (see Figure 4 on page 10-32) and warm-season turfgrasses (see Figure 5 on page 10-33) varies among the high-, medium-, and low-intensity maintenance plans. The amount of P and K recommended to be applied annually depends on the soil test level of these nutrients (Figure 6 on page 10-34), and whether the objective is to increase or maintain current levels.

Highly Water-soluble Nitrogen Sources

As their name implies, highly water-soluble nitrogen (WSN) sources release nitrogen to turf very quickly once in contact with water. These sources are less expensive per pound of nitrogen than controlled-release N sources, and they stimulate rapid aerial shoot growth. They are also more likely to cause foliar “burn” and leaching from the turfgrass root zone. To limit the potential for fertilizer injury, no more than 1 pound of WSN should be applied per thousand square feet per application.
Urea (46-0-0), ammonium sulfate (21-0-0 w/ 24% S), diammonium phosphate (18-46-0), monammonium phosphate (11-48-0), and potassium nitrate (13-0-44) are examples of WSN sources. Ammonium sulfate, monammonium phosphate, diammonium phosphate, and potassium nitrate are available in granular and, in some cases, sprayable forms.
Urea is formulated as a solid granule or hollow prill and may also be applied as a low-nitrogen-concentration foliar spray. Once turfgrasses are fertilized with granular or prilled urea, and if the soil is moist, this WSN source reacts quickly (usually within 7 to 10 days) with water to form ammonium-N (NH4+). The naturally occurring enzyme urease speeds this reaction. Ammonia (NH3) may volatize from urea, as well as ammonium-containing nitrogen sources. Nitrogen losses by ammonia volatilization as high as 30 percent have been reported from turfgrasses growing in highly alkaline soils. This is one reason that a faint ammonia odor is at times noticeable immediately after fertilizing turf.

Controlled-Release Nitrogen Sources

Although controlled-release N sources have a range of release rates, these “slow-release” fertilizers commonly contain a minimum of 50 percent of the total nitrogen in water-insoluble (WIN) form.
Urea formaldehyde and polymer-coated urea are examples of controlled-release N sources. Compared to fertilizers containing 100 percent WSN, controlled-release N sources are usually more expensive per pound of N, and the color responses and rate of turfgrass growth are more gradual following application. Advantages of using fertilizers with controlled-release N include less potential for N leaching and foliar burn plus fewer annual fertilizer applications. Application rates are often 1.5 to 2 times those of fertilizers with 100 percent WSN. Milorganite (6-4-0) is a natural organic (biosolid) source of controlled-release N and one of the oldest branded fertilizers in the US. Milorganite has been produced and marketed by the Milwaukee Metropolitan Sewerage District since 1926.

Irrigation

An actively growing turfgrass plant usually contains more than 70 percent water. Most of this water enters the plant through root hairs. As water moves throughout the plant, it carries with it essential mineral nutrients needed for growth and survival. It has been estimated that no more than 3 percent of the total amount of water that a turfgrass obtains from the soil is used to support photosynthesis.
Critically important biochemical reactions take place in water inside plant cells. Nutrients move upward in water through a vascular network of connected, nonliving plant cells, or xylem. The upward movement within the xylem is referred to as acropetal. Sugars and other energy-rich compounds move in solution from leaves to other plant parts including roots through a second vascular network composed of living cells, the phloem. The downward movement of nutrients and other compounds in solution via the phloem is referred to as basipital.
The total amount of water that evaporates from plant and soil surfaces and that the turfgrasses transpire is collectively referred to as the evapotranspiration (ET) rate. Evapotranspiration varies among actively growing turfgrass varieties or species and is influenced by the weather, usually ranging from 1/10 inch to as much as 3/10 inch of water daily. The evapotranspiration rate of a turf during cool, humid, cloudy conditions is usually much lower than the same turf exposed to high temperatures, drying winds, and direct sun. Wilting of plants and footprinting signal the need to irrigate. Drought-stressed turf often appears bluish-gray as it wilts, and plants are unable to quickly spring back when compressed by foot traffic.
Effective irrigation promotes turfgrass root growth when weather is favorable, and during periods of stress it preserves the roots. Enough water should be applied during each irrigation event to thoroughly moisten the entire turfgrass root zone while avoiding surface water runoff. To limit the amount of runoff from turf maintained on slopes or in soils high in clay having a low water infiltration rate (see Table 5), it may be necessary to set the irrigation system controller to start and stop watering a particular zone more than once as the turf is being irrigated.
In addition to environmental conditions, the amount of sand, silt, clay, and organic matter in a soil influence irrigation scheduling. Fine-textured, clayey soils usually hold more water for a longer period of time than coarse-textured, sandy soils. (see Chapter 5.)
Since excessively wet turf is prone to disease, watering at night and while dew is present should be avoided whenever possible. Although aerial shoots of turfgrasses irrigated in the afternoon usually dry quickly, much of the applied water may evaporate rather than moving through thatch and into the soil. The compromise is to irrigate in the morning. Irrigating during morning hours limits both evaporative water loss and the amount of time the turf canopy is wet.
When setting an irrigation controller to apply an appropriate amount of water to a particular turf area or zone, it is very important to determine how long it takes the irrigation system to deliver ½ inch of water. The time can be measured by placing several small containers (such as cups or tuna cans) about the same height as the turf at random locations throughout each zone. After the sprinklers have been activated for a known amount of time, the depth of water in each container is measured. For example, if an average of 1/3 inch of water is collected in a zone for a period of 10 minutes, the system output in the zone is 0.033 per minute (0.33 divided by 10). If the goal is to apply ½ inch of water per irrigation event, the sprinklers should be set to run for 15 minutes (0.5 divided by 0.033).

Dethatching

Turf management should focus not only on shoots and roots. The thatch layer also deserves attention. As turfgrasses grow, they produce new roots, leaves, and stems. When older roots and shoots die and are sloughed off, they serve as an important energy source for many beneficial soil microorganisms.
The rate at which this fresh organic matter decomposes varies depending on the turfgrass species and the temperature, moisture level, pH, and biological activity of the soil. Leaves usually decompose quickly compared to stems and roots. Nodes on stems and crowns are high in lignin and especially resistant to decay. Thatch accumulates on the surface of the soil when the rate of accumulation of dead organic material is greater than the rate of decay.
Healthy turf has some thatch. A managed thatch layer, unlike hard soil, is resilient and helps soften a fall by improving the impact absorption capacity of the turf. However, excessive thatch limits turfgrass rooting and restricts the movement of water into soil. Crowns, rhizomes, and roots located in a thatch layer rather than in the soil are no longer buffered against high and low temperature extremes. As a result, turf with too much thatch is prone to heat, cold, and drought stresses.
Generally, dethatching is recommended when turf develops ½ inch or more of thatch. Cool-season turfgrasses should be dethatched in fall or spring when turfgrass plants are actively growing. Bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass usually recover quickly when dethatched in early summer.
Small areas of turf can be dethatched using a hand rake specifically designed to slice into the turf canopy, dislodging and lifting a portion of the thatch and depositing organic matter on the turf surface. Powered walk-behind vertical mowers engineered to remove thatch work well when dethatching larger areas of turf. These machines have vertical blades or tines attached to a revolving shaft horizontal to and above the turf surface. They can be adjusted such that the blades or tines penetrate the thatch layer and lightly contact the soil below. The blades or tines dislodge and lift thatch as the vertical mower or “dethatcher” moves across the turf. Flexible-tine or spring-type machines, also referred to as power rakes, may not be very effective for thatch removal in dense, well-established zoysiagrass. The tines may flex or spring back when they contact the dense turf rather than penetrating the thatch layer.
Vertical mowers and power vacuums are available for lease at many outdoor power equipment or garden centers throughout Tennessee. After a vertical mower has been used, a power vacuum can remove dry, loosened organic matter from the turf surface. A recently dethatched bermudagrass turf is shown below. Note that linear grooves created by the vertical mower blades are visible after this turf was dethatched and after a turf vacuum had removed organic material from the surface.

Aerating

Turfgrasses are anchored in soil as their roots grow in pores among particles of sand, silt, clay, and organic matter. As foot and machine traffic passes over the turf, the soil surface can compress and lose porosity. Compaction can greatly impede water infiltration, nutrient penetration, and the exchange of CO2 and O2 between the soil and the atmosphere. Mechanical aeration is a means of alleviating soil compaction by “selectively” cultivating a portion of the turf surface.
Core aerifiers remove plugs of soil from the turf and create a coring grid or pattern of large channels through which O2, H2O, and nutrients can enter the soil. (see page 10-38.) Carbon dioxide and other gases move quickly from a well-aerated root zone into the atmosphere. In addition to relieving soil compaction, regular core aeration helps control thatch by preventing anaerobic soil conditions and maintaining a favorable environment for beneficial soil microorganisms capable of breaking down organic matter. Because of the aggressiveness of this turf care practice and the significant, yet temporary, disruption of the turf surface it causes, turf should be aerified when the weather is favorable and plants are actively growing.
Aerifying equipment may be leased at many outdoor power equipment or garden centers. Lawn care companies may also offer core aerification as a service.

Topdressing

Topdressing is the uniform broadcasting of a thin layer of sand, topsoil, or finely granulated organic material such as compost over the turf surface. This turf care practice dates back to the earliest days of golf course maintenance in Scotland. Today, many intensively managed golf greens and heavily trafficked sports fields throughout the state are routinely topdressed with sand to both smooth the turf and fill in damaged areas. Sand, due to its larger particle size, usually resists compaction better than silt or clay.
However, sand may not be the best choice of material to apply as topdressing to turf in home landscapes. Well-decomposed compost with uniform particle size can be topdressed immediately after core aerifying to increase the organic matter content of the soil. In addition to diluting heavy clay soils, the addition of organic matter below the thatch layer may improve a soil’s ability to hold moisture and nutrients. It has been estimated that a 1 percent increase in organic matter boosts the water holding capacity of 1 acre-foot of soil by about 6,000 gallons.

Rolling

Rolling a newly planted seedbed with a roller weighing as little as 100 pounds can improve seed contact with the soil. Similarly, light rolling immediately after sodding helps ensure that the sod is in direct contact with the subsoil below. Rolling may also help level turf lifted as a result of frost heaving or mole activity. However, because of the possibility of causing severe soil compaction, especially in turf growing in clayey soils, heavy rolling is generally not recommended when maintaining turf in home landscapes. A heavy roller should definitely not be used to correct surface undulations resulting from improper grading or planting bed preparation.

Turfgrass Pests

Diseases

The majority of microorganisms living in turfs are very beneficial. However, a few fungal pathogens are capable of injuring turfgrasses. Some of them infect leaves while others attack crowns and roots.
Several things must happen before a disease symptom appears in turf. The first is inoculation — the pathogen must come in direct contact with a susceptible turfgrass species or variety. Spores or mycelia often serve as the inoculum. The second is penetration — the pathogen must enter the turfgrass plant. Fungi enter turfgrasses through natural openings such as stomates, wounds caused by mowing, or by directly penetrating plant tissues. The third is infection — the process by which the fungus reproduces inside the plant and moves from cell to cell. Once infected, the turfgrass begins to suffer and visible disease symptoms appear.
Symptoms associated with several common diseases and vulnerable turfgrasses are presented in the supplemental tables on the website.
In addition to recognizing symptoms of common diseases of turfgrasses, it is helpful to know when the fungus causing each disease is most active. For example, dollar spot (Sclerotinia homeocarpa) and Pythium blight (Pythium spp.) often appear when it is hot and humid, while Rhizoctonia solani, the fungus responsible for causing large brown patch (shown on page 10-40) prefers warm, rainy, humid conditions.
Pythium blight is often more problematic in areas of turf that are poorly drained. Dew periods lasting longer than 8 hours favor mycelial growth of the pathogen that causes dollar spot. Although the disease red thread, caused by the fungus Laetisaria fuciformis, can develop throughout the year, it is most common in spring, late summer, and fall. Many varieties of Kentucky bluegrass are especially susceptible to this disease. Fungal pathogens (Ophiosphaerella spp.) that cause spring dead spot attack bermudagrass in the fall, although symptoms appear as dead patches of bermudagrass during spring transition from winter dormancy. Please note the presence of several species of turfgrass weeds in the bermudagrass turf injured by Ophiosphaerella korrae shown on page 10-40.

Insects

Turfgrass insects are often grouped according to their life cycle. The growth and development of some insects is described as complete, while the life cycle of others is referred to as simple, or incomplete (see Chapter 13). Insects with a complete life cycle have four stages of development: the egg; the immature form, or larva; the resting stage, or pupa; and the adult. Armyworms, cutworms, imported fire ants, billbugs, sod webworms, and white grubs are examples of turfgrass insects with a complete life cycle.
The life of an insect with an incomplete life cycle begins with an egg. Nymphs, resembling small, wingless adults, emerge from eggs and get larger after each of several molts, eventually becoming adults. Both nymphs and adults may feed on plants. The chinch bug is an example of a turfgrass insect having an incomplete life cycle.
Insects are also categorized according to the structure of their mouth parts. For example, armyworms, billbugs, cutworms, mole crickets, and white grubs damage turfgrass tissue as they chew. Chinch bugs cause damage as they pierce turfgrasses to access and extract cell contents.
Armyworm larvae (Pseudaletia unipuncta) feed almost exclusively on grasses, including turfgrasses. In Tennessee, armyworms produce four to five generations a year. Characteristics helpful when identifying this insect pest include a body that is mottled and varies in color from brown to dark green with alternating and contrasting stripes; a broad, dark band across the top of the body; and a small head with a brown, netlike pattern and dark arcs. Eggs are laid on turfgrass in masses or clusters covered with setae and scales from the underside of the female moth.
Each spring, fall armyworm moths (Spodoptera frugiperda) begin their northward migration from the southernmost US and Central America. This migration usually occurs over several generations before reaching Tennessee. Most years, damage from this pest is sporadic and light. When conditions are favorable for the pest, heavy damage from high populations can occur. For this reason, it is wise to sample for fall armyworms and other above-ground turfgrass pests regularly throughout the growing season. Use a solution of mild liquid dishwashing soap (as used for hand dishwashing in a sink) and water applied to the turfgrass. Two teaspoons of liquid dishwashing soap in 1 gallon of water should be poured over a 2-foot by 2-foot area. Observe the turfgrass for 10 minutes and collect any caterpillars, billbugs, or black turfgrass ataenius adults for identification.
Fall armyworm moths are attracted to light at night. Thus they tend to deposit many of their egg masses or clusters in areas partially illuminated by lights at night. The egg masses are usually laid on the grass and other host plants or on light-colored surfaces such as the side of a building, fence posts, and rails, shrubs, tree trunks and branches, stakes, flags, outdoor furniture, etc. The larvae vary and may be pinkish, yellowish-tan, greenish, or dark gray. There are four dark spots on the top of each abdominal segment. Larvae are about 11/8 inch (30 mm) long and 1/8 inch (4 mm) or more wide, and they have narrow and pale stripes along each side of the body. The head of a fall armyworm larva is dark colored with a contrasting yellowish-white inverted Y-shaped marking. Larvae feed on all above-ground plant parts. Both armyworm and fall armyworm larvae damage turf as they consume leaf tissue. Initially, individual leaf blades are skeletonized, and as larvae mature, all aerial shoots are consumed.
Billbug adults are beetles ranging from ¼ inch to almost ½ inch long. They have long bills or snouts with a pair of strong, nearly black jaws or mandibles at the end. Billbugs vary in color, often appearing reddish-brown or black. Billbug larvae are small, white, and legless. They have distinct hard yellow, tan, or brown heads. Mature larvae are about 5/8 inch long. Billbug adults chew into the base of turfgrass stems and insert their eggs. Larvae of the bluegrass billbug (Sphenophorus parvulus) most often injure Kentucky bluegrass, while those of the hunting billbug (Sphenophorus venatus vestitus) prefer zoysiagrass and bermudagrass. Both species complete their life cycle in one year.
First- and second-instar bluegrass billbug larvae feed inside the stem, eventually tunneling through the stem to reach thatch and soil, where they feed on crowns and roots. Damage usually appears from late June through early August as spotty, straw-colored patches of turf. Unlike bluegrass billbugs, which overwinter only as adults, hunting billbugs can survive winter as larvae and pupae as well. Larvae of hunting billbugs may continue to feed on bermudagrass or zoysiagrasses even after winter dormancy. As a result, symptoms of damage may occur in spring as the grass resumes growth. Patchy damage also may show up in the summer, especially during dry periods. Damaged turf will not green up following irrigation or rainfall.
Black cutworm moths (Agrotis ipsilon) deposit individual eggs on aerial shoots of turfgrasses. Larvae feed on all turfgrass species. Black cutworms overwinter south of Tennessee, and the strong-flying moths move into the state with spring storm fronts. Each year, up to four generations of black cutworms may be produced in Tennessee. Larvae often range in color from light gray to nearly black. Two black stripes are visible on the head. A pale line runs the length of the body, which often reaches a length of 1¾ inches (45 mm) and width of ¼ inch (7 mm). The body also has dark, paired, and uneven spots. Larvae usually develop within 20 to 40 days. They tunnel in thatch and feed at night. Their activity may result in many individual tunnels with each opening at both ends. As their name implies, black cutworm larvae chew leaves and stems at the soil surface.
Common chinch bugs (Blissus leucopterus leucopterus) are a pest of grass crops and turf and ornamental grasses such as bermudagrass, bluegrasses, bluestems, switchgrass, fine fescues, and ryegrass. They most often overwinter in tall bunch grasses in open fields or beneath plant debris. In spring, adult females lay eggs in turfgrass leaf sheaths. Very small bright red nymphs about half the size of a pinhead soon emerge from eggs. As they grow, nymphs shed their skin four times. When fully grown, the nymphs are black and have a white spot on their back between the wing pads. Nymphs are active in turf until late fall. Turf damage generally occurs during hot, dry weather from June into September. As chinch bugs pierce turfgrasses they secrete a substance that clogs xylem and phloem. Eventually, leaves wither and irregular patches of turf begin to turn yellow. The patches usually continue to expand outward and turfgrasses eventually die, even if the turf is being irrigated.
White grubs, the larvae of several species of scarab beetles, injure turf as they feed on roots or lift plants as they move through the soil. When white grub populations are high, damaged turf is easily rolled back because of its lack of roots. Larvae of green June beetle (Cotinis nitida), Japanese beetle (Popillia japonica), May and June beetle (Phyllophaga spp.), northern (Cyclocephala borealis) and southern (Cyclocephala lurida) masked chafers, and the very small, black turfgrass ataenius (Ataenius spretulus) are common in Tennessee. When disturbed, larvae, such as the green June beetle shown on the adjacent page, often assume a curled, C-shaped position. White grub species can be distinguished by the pattern of short hair-like setae on the raster of the grub. For example, note the irregular pattern of bristles on the raster of the masked chafer larva. Japanese beetle larvae have short setae in a V-shaped raster pattern, while May and June beetles have setae forming a pair of straight or curved rows.
May and June beetles in Tennessee complete their life cycle in two or three years. During the first summer, the tiny first instar larvae eventually molt into second instar larvae that overwinter. In a two- year life cycle, most of the root feeding damage is done in the following spring and summer by second and third instar larvae before they pupate and become adults. If a third year is needed to complete development, the third instar larvae overwinter and resume root feeding during the following spring and summer before pupating in late summer and becoming adults by October or November. Annual white grub species, including the green June beetle, Japanese beetle, and northern and southern masked chafers, complete their life cycle in 12 months or less.

Weeds

Ralph Waldo Emerson described a weed as “a plant whose virtues have never been discovered.” Another definition is “any plant growing where it is not wanted.”
Weeds compete with desirable plants for water, nutrients, sunlight, and space. Unlike many taller “agronomic” weeds found in row and cereal crops, turfgrass weeds are tolerant of routine mowing. They are grouped according to their form as grasses, broadleaves, sedges, or rushes. A turfgrass weed may be a summer annual, winter annual, biennial, or perennial.
Summer annual grassy weeds in Tennessee turf include barnyardgrass (Echinochloa crusgalli), large (Digitaria sanguinalis) and smooth (Digitaria ischaemum) crabgrasses, crowfootgrass (Dactyloctenium aegyptium), goosegrass (Eleusine indica) (see page 10-44), and giant (Setaria faberi), green (Setaria viridis), and yellow (Setaria glauca) foxtails.
Summer annual broadleaf weeds commonly found growing in turf throughout the state include black medic (Medicago lupulina), common lespedeza (Kummerowia striata), eclipta (Eclipta prostrata), prostrate knotweed (Polygonum aviculare) (see page 10-44), prostrate spurge (Euphorbia supina), and purslane (Portulaca oleracea).
Winter annual grassy weeds such as annual bluegrass (Poa annua) (see page 10-45) and annual ryegrass (Lolium multiflorum) are very easy to see in dormant warm-season turf. However, they may be much less obvious in cool-season turf until they reach physiological maturity and form seed heads. Annual bluegrass resembles Kentucky bluegrass with one major exception. Unlike Kentucky bluegrass, annual bluegrass does not form rhizomes. A prolific seed producer, the short, open panicle seed heads of annual bluegrass are visible in many turf areas each spring.
Common chickweed (Stellaria media) (shown on page 10-46), corn speedwell (Veronica arvensis), field madder (Sherardia arvensis), and two members of the mint family, henbit (Lamium amplexicaule) and purple deadnettle (Lamium purpureum), are examples of common winter annual broadleaf weeds.
Dallisgrass (Paspalum dilatatum) (see page 10-46), nimblewill (Muhlenbergia schreberi) (see page 10-47), and the forage species orchardgrass (Dactylis glomerata) are (and have historically been) common perennial grassy weeds of residential turf throughout Tennessee.
Common creeping perennial broadleaf weeds of turfs include ground ivy (Glechoma hederacea) (see page 10-47), Indian mock strawberry (Duchesnea indica), thymeleaf speedwell (Veronica serpyllifolia), Virginia buttonweed (Diodia virginiana)(see page 10-48), and white clover (Trifolium repens).
Globe sedge (Cyperus globulosus), purple nutsedge (Cyrerus rotundus), yellow nutsedge (Cyperus esculentus), false-green kyllinga (Kyllinga gracillima), and green kyllinga (Kyllinga brevifolia) are perennial weeds with triangular stems and members of the sedge family that resemble grasses upon casual observation.
Path rush (Juncus tenuis), a weed of turf maintained in soils that remain wet for extended periods of time during the year, is just one of more than 300 Juncus species. A branching inflorescence from about ½ inch to 3 inches across is suspended atop each flowering stem of mature plants.

Pesticidies

Formulation

Fungicides, insecticides, and herbicides labeled for use in home landscape turf are marketed in several forms, including granule (G), liquid (L), water-dispersible granule (WG), suspension concentrate (SC), emulsifiable concentrate (EC), and microemulsion (ME).

Mode of Action

Pesticides are often grouped or categorized based on their chemical structure and mode of action (MoA), the way in which the active ingredient works to inhibit or eliminate a particular fungus, insect, or weed. The mode of action of a pesticide is an important consideration when managing the potential for chemical resistance in fungal, insect, and weed populations. It is recommended that multiple MoAs be used to manage a given pest, either in rotation or mixtures with one another.

Pesticide Resistance

The active ingredient in a pesticide may act in only one way (called single-site activity) or several ways (multisite activity) to control the targeted turfgrass pest. Since a pesticide with multisite activity has a number of effects or impacts on a pest, the risk of the pest developing resistance to the applied pesticide is low compared to a pesticide with single-site activity.

Pollinator Protection

Several preemergence and postemergence herbicides are labeled for use in home lawn turfs to control weeds that attract pollinators. Mowing turf in which weeds such as dandelion and white clover are flowering before applying an insecticide will remove flowers, reduce pollinator foraging and limit the potential of pollinator injury from direct exposure to the insecticide. Maintaining a “no insecticide treatment” buffer strip (for example, a strip of turfgrass 2 to 3 feet wide) between treated turf and the edges of landscape beds minimizes the potential for unintended uptake of a systemic insecticide by roots of flowering ornamentals.