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Chapter 15: turfgrass.

KEY TERMS

core aeration plugging rotary mower spiking sprigging thatch

We can all appreciate the lush, luxuriant look and feel of a healthy green lawn surrounding the typical residence. This is the idealized image of the American dream home. For many homeowners, the more turf and the greener and healthier it looks, the closer they feel they have come to perfection in a landscaped yard. A healthy, green lawn is so much a part of the quintessential American residential landscape that even in places where turf is difficult and impractical to grow, such as the American Southwest, it is still viewed as the ideal, if not the norm. Many homeowners in these places have at least a spot of turf, if not entire front and back yards covered with it (Fig. 15-1).

Turfgrass is the all-purpose groundcover that is used throughout the United States. In addition to home lawns, many outdoor public spaces such as golf courses, parks, cemeteries, and athletic fields provide a carpeted green landscape over much of our inhabited land (Fig. 15-2). Some estimates place the acreage of turfgrass at 50 million acres in the United States alone. There are several reasons for the success of turf as a groundcover:

* It spreads readily into the desired area.

* It tolerates repeated pruning.

* It offers visual negative space that nicely counterbalances the colors of flower beds.

* It tolerates and recovers from being tread upon, even to the extent of being torn up on athletic fields.

* The fine root system holds soil in place and helps to prevent erosion.

* It can be used to cover slopes, in moist areas, and to some extent in shade.

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Turfgrass provides many other benefits not directly related to its use as a groundcover, such as the following:

* Cools the air through evapo-transpiration (water loss through leaves)

* Absorbs C[O.sub.2] and produces enough oxygen for a family of four (2,500 square feet of lawn)

* Absorbs rainfall and reduces runoff more efficiently and effectively than driveways and other hard surfaces

* Is safer and less injurious than artificial turf

* Contributes 5% to 15% in overall property value if well maintained

Although turf can appear to be relatively carefree, there are many factors that contribute to the success or failure of a healthy green lawn. An understanding of how turf grows, what its requirements for healthy growth are, and what seasonal activities can be implemented to optimize turf growth will result in the lush, beautiful lawn that is so idealized in our minds.

TURFGRASS STRUCTURE

Turfgrass is a monocot and belongs to the grass family, Poaceae. One way that many turfgrasses differ from ornamental grasses is that they form a thick sod rather than a clump. Blades are comparatively thin, measured in a few sixteenths of an inch. Blade width is what imparts the overall texture to a lawn or other turf area. Turfgrasses are generally mowed to a height of less than 1/2 inch to about 3 inches.

Turf can tolerate mowing, in part, because of the location of meristems. Meristems are growing points in the plant where cell division and new growth takes place. There are two main meristematic regions on turf: the crown and the inter-calary meristem (Fig. 15-3). Leaves continue to grow from these positions low on the plant, as long as they are not damaged by mowing or other practices. Scalping on a lawn results in turfgrass death because the meristematic regions are destroyed.

The crown is the white tissue located between the leaf stem and the roots. Growth here results in both new leaves and new roots (see Fig. 15-3). In addition to the crown, a grass plant is made up of leaf blades that are attached to the crown with a sheath and a fibrous root system. New leaves develop inside the sheath within older leaves. Cell division at the base of the leaf results in leaf elongation. Thus, mowing the tip of the leaf removes only the older tissue of the leaf. When one is mowing, it is important not to remove the base of the leaf where new growth occurs; otherwise new leaves will no longer develop. Grasses flower from the center of the plant on a special stalk called a flowering culm (Fig. 15-4). Flowers are usually in a panicle inflorescence.

Turfgrasses may be clumping or spreading. Spreading types may produce stolons or rhizomes; both are types of specialized stems that grow in a horizontal fashion. Stolons grow above ground and are also called runners. Rhizomes grow underground and periodically produce new shoots and roots. Some rapidly growing grasses develop one or both of these modes of growth. Tillers are new upright shoots that are produced by clumping-type turfgrasses (Fig. 15-5). Tiller-forming, clumping-type turfgrasses may spread, but they often do not spread as rapidly into new areas as do spreading-types that have rhizomes or stolons.

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TURF QUALITY

The beauty of turf comes from its four main characteristics: color, texture, density, and uniformity. The ideal color is medium to dark green or the bluish green exhibited by Kentucky bluegrass. Perennial ryegrass, bermudagrass, and tall fescue tend to be lighter green than bluegrass. Fine fescue tends to be darker green in general.

Whereas the texture of turfgrasses varies greatly, finer textures are generally considered more aesthetically pleasing than coarse textures. Fine-textured turf also feels soft to the touch. Tall fescue is quite coarse, but breeding efforts to select finer textured cultivars are ongoing. Fine fescues and bermudagrass are fine-textured grasses, whereas bluegrass and ryegrass are medium-textured. Zoysia cultivars can be fine, medium, or coarse textured.

A dense turf area feels soft and luxurious to walk on. Density is a function of turf grass health and vigor. A vigorously growing dense turf can out-compete weeds and is most desirable. Uniformity is a function of species, color, texture, and density. A mix of turf species could result in a variety of texture and color, and a random mixing of different turf species does not necessarily provide the desired result. Commercially available mixes are usually designed to provide uniform texture and color. Finer textured bluegrass cultivars are combined with fine fescue to provide greater overall uniformity in sun-shade mixes.

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TURF GROWING REGIONS

Much like ornamental grasses that flower in summer and go dormant in winter, when the leaf blades turn tan or brown, turfgrasses have active and dormant periods, too. These periods just are not as noticeable because many turfgrasses do not turn brown when they are dormant. They tend to maintain their usual color and may even have root growth when leaves have stopped growing. A few turf grass species that turn brown during their dormant season are zoysia and buffalograss.

The United States can be divided into distinct regions on the basis of temperature and moisture, and these factors determine which species of turf will perform best there. Figure 15-6 shows a map of the United States that delineates five climatic regions. The eastern portion (regions 1, 2, and 3) and the northern West Coast (region 6) of the United States are fairly moist areas, whereas the western portion (regions 4 and 5 and the western portion of 2) tend to be arid. The northern regions (1, 6, and parts of 4 and 5) are cool-season areas for turf, whereas the southern regions are warm-season areas.

SPECIES: WARM-SEASON AND COOL-SEASON

The dormancy period for a turfgrass varies by species. Major turf species grown in the United States are classed into roughly two types: warm-season and cool-season grasses. Cool-season and warm-season grasses have different life cycles, and, thus, differ in the timing of cultivation practices that are applied to them. See Fig. 15-7 for a general depiction of warm- and cool-season turf life cycles. Table 15-1 shows the major turf grass species that are commonly grown in the United States.

Warm-Season Grasses

Residents of the south and west will use warm-season turfgrasses. These include bermudagrass (Cynodon spp.), and zoysia (Zoysia spp.). Buffalograss (Buchloe dactyloides) is appreciated for its drought and heat tolerance in arid areas of the western United States. St. Augustinegrass (Stenotaphrum secundatum) is grown in some hot, subtropical areas of the deep south. Improved bermudagrass hybrids are widely used for golf course tees and greens (Table 15-2). Bermudagrass is considered a low-maintenance grass (Fig. 15-8, see page 359).

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Cool-Season Grasses

Northerners, easterners, and many midwesteners use mainly Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), and fine, or red, fescues (Chewing's, sheep, and creeping red fescue) (Festuca spp.). Tall fescue (Festuca arundinacea) is used to some extent in the north and in the transitional zone. Of these, the fine fescues tolerate some degree of shade and are often included in shady mixes available at lawn and garden centers. Tall fescue is a deep-rooted species that tolerates periods of drought well. Bluegrass is a fine-textured turf species that is available in a multitude of cultivars. (Table 15-3, see page 362). Creeping Bentgrass (Agrostis palustris) is widely used on putting greens in the cool-season zone. Occasionally it is used as a lawn grass, but it requires very high maintenance.

SELECTING SEED

When selecting seed, check the label to see what species are included and at what percentages. The seed label lists the origin of the seed, germination percentage, presence of weed seeds, and other material. Most of the turf grass seeds sold in the United States are grown in the northwestern United States.

A blend is a combination of cultivars of the same species, whereas a mix is a combination of different species. Many improved cultivars have been developed in the major turfgrass species. There are more disease- and pest-resistant cultivars, as well as improvements in textures for the coarser-leafed tall fescue. The advantage of a blend is the ability to obtain tolerance to a variety of disease and pest problems within a single species. The cultivars complement one another in their improved qualities. The advantage of a mix is similar, with the additional, and often greater, differences in germination, recuperative ability, and ability to withstand wear. Some species mix better than others. To mix well, species should have similar texture and color. Kentucky bluegrass and perennial ryegrass are often combined in mixes. Sometimes red or fine fescues are added, particularly if some degree of shade tolerance is desired. Tall fescue, zoysia, and bermudagrass do not mix well with other species. Table 15-4 (see page 362) shows a list of mixes and blends of turf.

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ESTABLISHING A NEW LAWN

The new lawn may come from a variety of methods, with seeding and sodding being predominant. Of the two, sowing seed is cheaper, and it can be applied to irregularly shaped areas. Sowing seed is fairly easy to do. Sod laying can be painstaking work but provides instant green coverage. Even though sod costs more initially, it does eliminate the many problems one may encounter with seed establishment, such as damping-off of seeds, birds eating the seeds, poor establishment due to irrigation problems, and weed problems. With sod, a more limited selection of species and cultivars is available than with seed. Either method will require some special care, preparation of the planting area, and a period of establishment.

Two other methods of turf establishment are sprigging and plugging. Sprigging and plugging are vegetative propagation techniques that take advantage of turf species that reproduce by stolons, such as bermudagrass, or grow vigorously from tillers, such as zoysiagrass. Sprigs are pieces of stolons, perhaps with roots and shoots attached. They are spread over a prepared area and firmed into the soil (Fig. 15-9, see page 363). Plugging involves removing a plug of turf from one area and planting it into a prepared area (Fig. 15-10, see page 363). Eventually, the sprig or plug will grow into the surrounding area. The advantage of these two methods is that they require much less plant material to establish an area than sod. Also, these methods work well in irregular areas in or small areas that do not require much sod.

Soil Preparation

Whether sodding or seeding, the ground preparation is similar. Remove unwanted plants, large objects, rocks, and debris. Ensure that the area is level, with a gentle slope away from the house or building. Perform a soil test to determine whether the pH requires amending or fertilizer is needed. If so, then incorporate these when cultivating before planting. This is also a good time to install any drainage away from the house that might be required. For example, install drain tiling from the gutter downspouts to move excess water out of the lawn area.

Cultivate the soil to a depth of 8 to 10 inches. This cultivation is best accomplished with a small tractor or a rototiller. Be sure to break up any clods or large pieces and remove larger rocks, as these will interfere with the seed-soil contact required for germination. Rake gently to fill in any depressions and smooth out bumps.

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Seeding

The first step is selecting the best seed for your site. In addition to choosing the appropriate species and cultivar(s) for the quality, maintenance level, and purpose you desire, use care in purchasing the actual seed. Read the label to ensure the seed does not contain undesirable weed seeds or other material. Check also for the date of the germination test to ensure that the seed is fresh. The seed package will provide the seeding rate. If you purchase bulk seeds that do not provide this information, refer to Table 15-5 for approximate seeding rates for your species.

Seeding should be done at the time of year that allows for maximum growth before complete dormancy to give the turf a chance to become well established and better able to out-compete with weeds in the area. For cool-season grasses, the best time to establish turf is in September. For warm-season grasses, the best time is June.

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Planting. Seed may be applied by broadcasting in an area or using a gravity- or drop-type spreader (Fig. 15-11).

When spreading seed, more uniform placement can be achieved by dividing the seed in half and applying half of it in a north-south direction and the other half in an east-west direction (Fig. 15-12). Very small seeds may be mixed with sand or soil for ease of distribution.

After spreading, the seed should be lightly raked in. The main purpose of this raking is to ensure good seed-to-soil contact. Even if the seed is not actually touching the soil, it requires the moisture that is available there for germination.

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Mulching. Adequate moisture is maintained by covering the area with straw, shredded newspaper product, or other products designed for this purpose. Although straw is relatively inexpensive, it has the disadvantage of blowing around and may look quite messy. Netting of various materials is available, as are other products. Do not cover the seeds with an excessively thick layer of straw. The purpose of the mulch is to maintain a constant level of moisture during seed germination, but the seedlings also will require light when they emerge. Too much straw may reduce the stand that emerges.

Irrigation of Seedlings. The critical time for irrigating a newly seeded lawn is during the seed germination process. Seeds must not be allowed to dry out during the germination process, or all will be lost. Once the radicle has emerged and new roots are growing through the soil where they can pick up available moisture, then watering can be reduced as needed. If perennial ryegrass and Kentucky bluegrass are used together in a mix, use caution when deciding when to turn off the water. Perennial ryegrass should be up within 1 week, whereas the bluegrass may take 2 weeks or longer to germinate.

Post-Planting Care. Mulch is valuable for moisture retention during the germination process. Once the grass is established, the straw or other mulch may be removed. Of course, it may be left in place to decompose, as well, if a layer that was not too thick was placed there. The grass should have no trouble emerging from the straw layer.

Traffic on the new lawn area should be kept to a minimum. Mowing should be done when the grass is about one-third longer than its desired height. New grass seedlings are very sensitive to herbicides, so they should not be used in the first year.

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Sodding

Sod is purchased from local companies and laid the day it arrives. It is harvested very shortly before installation. Sod is expensive and is usually laid by landscape or lawn services companies. To lay your own sod, prepare the ground in the same manner as described for seed establishment. The time of year for sodding is the same as for seed establishment.

Selection. Species selection for sodding is more limited than it is for seeding. Fewer species and cultivars can be grown as sod, and sod growers must by necessity limit their selections. Find a reputable sod grower in your area, and research the species and cultivars they have available. You may need to order sod through your local nursery. The most commonly grown sod species are Kentucky bluegrass in cooler climates and bermudagrass in warmer climates. Roadside mixes may contain tall fescue.

You should use the sod within 1 or 2 days of receiving it. Sod is a living carpet of grass that is respiring. It is usually rolled or folded into mats and stacked on pallets. Respiration increases the heat in the sod stack. Thus, if you cannot use the sod immediately, it should be placed in a cool, shady location until it is used. It is permissible to sprinkle the sod with water if the weather is very hot but do not allow the sod to become soggy or overly wet.

Thick sod has more soil and roots and is more drought tolerant, but thin sod roots more quickly and is lighter to handle. Washed sod has had all the soil washed away from the roots.

Laying sod. Moisten the soil before laying sod (Fig. 15-13). Use care when handling sod so that it does not become stretched in one direction or another. If sod becomes stretched the edges will dry and leave gaps between seams. Seams within a row of laid sod should be offset from seams in adjoining rows, using a running bond pattern (Fig. 15-14). Pegs should be used when sod is placed on slopes or hillsides.

Irrigation of Sod. Irrigation is the final step in sod laying. A good soaking each day for 7 days is optimal. Turf generally requires 1 inch of water or rainfall per week. Sod will root into the new site in 1 to 2 weeks. Once rooting has occurred, irrigation can be reduced.

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REGULAR MAINTENANCE

Mowing

The most common lawn mower is the rotary mower. The blade rotates parallel to the ground. These may be walk-behind mowers or riding lawnmowers. Walk-behind mowers may complement riding mowers because they are easier to use to trim up small areas. Lawns are typically mowed once every 1 to 2 weeks, depending on rainfall and the level of maintenance desired. If a higher maintenance lawn is preferred, then more irrigation and fertilizing are used, resulting in the need for more frequent mowing.

Turfgrass species can contribute to the need to mow more or less frequently. For example, bermudagrass and bluegrass grow more vigorously than fine fescue or perennial rye. The former species spread by rhizomes and/or stolons, whereas the latter tend to be tillering types. The ideal mowing height for each species is provided in Table 15-6. As mowing height increases, root mass also increases. Thus, a taller lawn results in a more drought-tolerant grass. Shorter turfgrass has shallower roots. For the most energy-efficient lawn, grow turf at the higher levels and mow as infrequently as possible. Avoid mowing turf short and then allowing it to get quite tall before mowing it short again. This is stressful to the plants and may lead to insect and disease problems.

Irrigation

Cool-season grasses go dormant during hot, dry weather. During this time they will continue growing if they are irrigated. If not irrigated, they will come out of dormancy when regular rains return. To keep cool-season grasses growing during the dry dormant season, provide at least 1 inch of water per week. Deep, prolonged watering is recommended over shorter, shallower watering, as it is a more efficient use of water and also allows deeper root growth. The ideal time to water turf is early morning. This minimizes water loss due to evaporation. It also avoids prolonged moist conditions that benefit pathogen survival, growth, and spread as would occur if watering were done in the evening or during the night. Warm-season grasses also require approximately 1 inch of water per week during the growing season. Some of this may be provided by rainfall, so the actual amount applied may vary accordingly.

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Fertilizing

Because vegetative organs (i.e., leaves) are the primary tissue desired in turfgrass, nitrogen is the primary fertilizer required for optimal green growth. Provide approximately 1/2 to 1 pound of nitrogen per 1,000 square feet during or just before the growing season to encourage vegetative growth. In addition to supporting growth, this fertilization will provide a competitive edge to the turf over weeds and protect it from invasion by weeds. Do not overapply nitrogen, as this will result in rapidly growing and weak plants that will then become more susceptible to diseases and pests. Potassium provides a balance to nitrogen and counteracts its effects.

Phosphorus is applied during seeding to aid root establishment. Potassium is applied at higher rates in fall for cool-season grasses and in early summer for warm-season grasses. Potassium is valuable for root growth, which continues to occur as long as the ground is not frozen in cool-season climates. It is applied at a 1:2 nitrogen/potassium ratio. The stronger root system that results increases disease and pest tolerance and permits carbohydrate storage that will be drawn upon during the greening-up period in the spring. This so-called winterizing fertilizer is a valuable component of a fertilizing scheme for cool-season turf. It is equally valuable for warm-season grasses; however, their ideal growing time is July to August.

Fertilizer is normally applied as a granular form using a drop-type spreader (see Fig. 15-11) or a rotary spreader (Fig. 15-15). Water-soluble fertilizer may be applied using a hose-end sprayer.

Aeration

Aeration is a technique used on compacted turf areas. This benefits underlying roots by allowing air to penetrate and also increasing water percolation. Core aeration and spiking are two methods of aeration. Core aeration involves the use of equipment with hollow tines that removes small cores of turf, thatch, and soil. The cores may then be raked back over the area or removed. Spiking involves the use of solid tines that simply poke holes into the turf surface. There are no cores of soil brought up with this method. In either case, a topdressing of fertilizer may be applied at this time.

RENOVATING THE NEGLECTED LAWN

Renovation is the practice of reseeding a lawn while leaving the current lawn intact. This practice may be required because of serious weed or pest infestation or overall decline of the turf area. Existing plant cover may be killed with a nonselective herbicide and then overseeded with desirable turf seeds. If pests are present in the soil or declining turf area, they must be eradicated before renovation.

PROBLEMS

Turfgrass areas suffer from a wide variety of problems that include growth of the wrong species in a location, poor soil, poor management practices, poor fertility, and disease and pest infestations (Fig. 15-16). Some of these problems are interconnected. For example, poor fertility that is not managed adequately can result in weed infestation in poorly growing turf. Turf species that require full sun will perform poorly in shady areas.

Pests

Some common turf pests include grubs (Japanese Beetles and others), mole crickets, sod webworms, and chinch bugs. It is important to understand the life cycle of each pest to provide optimal control. For example, grubs are C-shaped larvae that overwinter in the soil where they feed on turf roots (Fig. 15-17). As the ground freezes, they move below the frost line in the soil. In spring they migrate back upward before emerging as adults. Adults are above ground for several weeks while laying their eggs. The best time to control grubs is when they are actively feeding on roots close to the surface of the soil and when they are at the youngest stage of larval growth. This usually occurs during late summer, in August to mid-September. The optimal time to apply grub control varies by location and climate, so check with local extension offices or lawn and garden centers to learn the most appropriate time to control grubs in your area.

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Sod webworms create tunnels in thatch or the soil directly under turf. The tunnels are lined with silk that joins together particles of soil and turf leaf blades. Larvae emerge from their tunnels, usually at night, and feed at the base of the grass blade, cutting it off and creating brown patches in the lawn. Adults do not cause any damage so the larval stage is the one to control.

Mole crickets are a major pest in the South (Fig. 15-18). They overwinter in the soil and mate in early spring. While they feed on plant roots, they cause even more damage by tunneling through the soil. Chinch bugs are piercing-sucking pests that insert their mouthparts into turf leaves to feed. As they feed, they release a toxin into the plant that causes the leaves to turn yellow and later brown.

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To test for turf pests, one method that often works is the coffee can method. Cut both ends out of a medium-sized can to create a tube. Insert one end of the can into the soil about a half inch or so, then fill it with water. Pests that are present in the soil or grass will float to the surface. Other techniques are to tug on the grass leaves and see if they separate easily from the roots. This is usually a sign of sod webworms. Another technique is to cut a square foot of turf and dig about 2 to 4 inches deep to remove the square. Pests living in and below the root surface may be detected this way.

Diseases

In turfgrasses, most of the common diseases are caused by fungal pathogens. Moist, humid conditions often favor their growth and spread. Tools and equipment or even shoes can spread fungal spores. Thus, care must be taken when dealing with these pathogens. Some common fungal pathogens of turf include leaf spot, brown patch, dollar spot, red thread, snow mold, summer patch, and take-all patch.

To reduce the incidence of fungal infestation, water early in the morning. This allows the grass to dry before nighttime and minimizes the period of time the grass remains wet. Humidity is not a controllable factor, and times of high humidity favor fungal growth. This is particularly true when dew remains on grass for extended periods, during periods of high humidity and high dew point temperatures. High nitrogen fertilization can also create plants that are more susceptible to disease infestation. Potassium fertilizer can counteract this weakening effect of nitrogen.

Weeds

Weeds are a problem when turf is not growing adequately to achieve optimal density. This inadequate growth occurs in moist areas or shady areas or when fertility is low, when soil is compacted, or where turf is diseased or damaged (Fig. 15-19). Table 15-7 provides information about some problem spots that occur in turf areas and the weeds that invade there. If lawn weeds are a common problem, the fertility program should be evaluated, and soil should be checked for compaction and wet areas (Figs. 15-20 to 15-22). As trees grow, the shady areas they produce become more extensive, and the turfgrass under them fails to thrive. In such cases, shade-tolerant turf or other groundcovers may need to be introduced.

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Weeds in turf are controlled with different chemicals, depending on whether they are monocots, like the turf itself, or dicots, otherwise referred to as broadleaved weeds (Fig. 15-23). Monocot weeds in turf include crabgrass, nutsedge, tall fescue, wild garlic, and annual bluegrass. Broadleaved weeds in turf include dandelions, creeping Charlie, ground ivy, henbit, plantain, and clover. Table 15-8 shows different types of weeds found in turf areas.

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Herbicides. Use selective herbicides for broadleaf control such as dandelions and creeping Charlie. Nutsedge and wild garlic are monocots, so broadleaf controls will not work on them. Instead, use pre-emergent herbicides to control annual grassy weeds in turf. Some herbicides, such as dimethyl tetrachloroterephthalate (DCPA) and dithiopyr, are labeled for monocot weeds in turf. Both annual and perennial monocot weeds may require post-emergent applications of a nonselective herbicide. A systemic herbicide will provide the best control. Use a spot-treatment approach, and avoid spraying in windy conditions so as not to damage the turf during application.

Newly planted turf should not be subjected to herbicide of any kind, as it is very sensitive for the first year. Pre-emergent herbicides may be used before sodding. Broadleaved weeds may also be partially controlled using pre-emergent herbicides but will probably also require application of a product containing 2, 4-D, methylchlorophenoxy acetic acid (MCPA), triclopyr, or dicamba. In addition to chemical controls, the underlying cause of a weed problem should be examined and addressed for optimal long-range control. If compaction, low fertility, or use of the wrong species are not corrected, then the weed problem will recur.

Thatch

Many people have the misconception that thatch is from grass clippings that are left on the lawn during mowing. This is not true! Thatch develops from grass plant tissue that accumulates between the base of the plant and the roots. It is composed of partially dead and decomposed tissue and undecomposed tissue. It forms from rapidly growing turf species or under high fertilization and irrigation schemes. The former include species such as bermudagrass, fine fescue, zoysiagrass, and St. Augustinegrass whereas the latter applies to bentgrass on golf courses. Thatch has tillers, rhizomes, and/or stolons in it.

Thatch is visible as a tan-colored mat beneath the green leafy tissue. It is detectable as a spongy feeling when you walk on the turf. Thatch builds up when growth outpaces decomposition of older tissue. A thin layer, up to a half-inch or less is acceptable, but beyond that, it can lead to several problems.

Problems associated with thatch include difficulty with mowing because the wheels of the lawn mower sink into the thatch. Sometimes this leads to scalping. Thatch prevents water retention and can cause droughty conditions in the root environment. It causes a situation of low fertility and impedes herbicide and pesticide movement into the soil.

Correcting thatch lies in part in correcting the conditions that lead to thatch. If the pH is too acid or alkaline, turf will die faster than it grows, and decomposition is slower. The optimal pH for turf is 6.0 to 7.0. Wet, compacted, and poorly drained soils can lead to thatch buildup. Techniques that can help reduce or remove thatch are vertical mowers, specialized equipment that has blades to cut through the thatch layer. For cool-season grasses, vertical mowing should be performed in late summer to early fall; for warm-season grasses it should be performed in late spring to early summer (Fig. 15-24).

Topdressing is the application of topsoil over the top of the grass. The soil settles into the thatch layer and allows decomposition to proceed at a greater rate. This method helps to break down the thatch and is an effective solution to the problem, although it can be a costly method to use. Another method is to purchase thatch-decomposing microorganisms.

SEASON OF ESTABLISHMENT AND MAINTENANCE

Most turf activities for warm-season species should be performed in the summer, during the period of active growth, or during the spring, immediately before active growth. For cool-season species, most activities should be performed in fall, but some are successfully accomplished in spring. Summer is a time of dormancy for cool-season species and is a less-than-ideal time for fertilizing, establishment, core aeration, and other activities. However, if you are growing a high-maintenance lawn, then you should continue to irrigate throughout the summer months, providing about 1 inch of water each week.

TURFGRASS ALTERNATIVES

Using a turfgrass alternative may be appropriate for areas that are difficult to mow, such as slopes or perpetually wet areas, for shady areas that cannot support turf growth, in garden areas, or for very large areas. For these reasons and perhaps for aesthetic reasons too, alternative groundcovers may be more desirable than traditional turf. Some of the requirements for use of a turf alternative are the ability to grow low enough so as not to require mowing and to remain attractive throughout the year. The latter requirement makes selecting a turf alternative in colder areas more difficult because many nonturf groundcovers are deciduous or will die back in winter. Of those that are used to cover slopes, many are not mowed or tread upon. For example, wintercreeper and vinca, or myrtle, are commonly used in areas where mowing would be difficult. In warmer climates mondo grass is sometimes used as a groundcover that does not require mowing, but also cannot tolerate being tread upon. Table 15-9 shows a list of groundcover species that can replace turf in difficult areas such as under trees or on slopes that are too steep to mow. See Table 17-3 for additional groundcovers.

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SUMMARY

Turf is a great groundcover that tolerates being trodden on and repeated pruning, from which it generally recovers quite well. However, it is not as easy to grow as it may sometimes appear, as is evidenced by the many turf areas that, upon closer inspection, are filled with weeds. Different turf species are used in different regions, as well as sunny versus shady sites. Turf does not tolerate wet conditions, compacted soil, or dense shade very well.

Turf is grown for its foliage and thus requires medium to high levels of nitrogen, especially during the growing season. Potassium helps grow a more extensive root system, providing higher levels of tolerance to pests and diseases. Phosphorus aids in seedling establishment.

Seeding and sodding are the primary methods used to establish turf areas, although sprigging is used in some areas with zoysiagrass. Close attention to fertilizer needs and avoidance of problems such as compaction will help to ensure a strong and healthy turf area.

HANDS-ON ACTIVITIES

* Collect turf specimens from unmown areas, including floral structures, if possible. Identify leaf, floral, and other plant structures using a drawing for reference. Identify the blade, ligule, sheath, crown, root, rhizome, and stolon, if present.

* Germinate seeds from different turf species for identification purposes and to observe the various plant structures closely.

* Grow two turf plots with different densities and observe weed problems

* Collect weeds from problem turf areas and identify groups of weeds that appear under certain conditions (e.g., wet, compacted, dry, or low fertility).

REVIEW QUESTIONS

1. List three reasons turfgrass is successful as a groundcover.

2. List three advantages of a well-maintained lawn.

3. What is the function and effect of the intercalary meristem?

4. Discuss the various ways turfgrasses can spread and grow vegetatively.

5. Name and discuss the turf qualities of color, texture, density, and uniformity.

6. Discuss warm and cool turf growing regions and name the turf species grown in each.

7. What is sprigging? Plugging?

8. What information is provided on a seed label?

9. What benefits are provided to lawns by nitrogen? Phosphorus? Potassium?

10. What is thatch?

SELECTED REFERENCE

Emmons, R. (2000). Turfgrass science and management (3rd ed.). Clifton Park, NY: Thomson Delmar Learning.

Dr. Marietta Loehrlein currently teaches horticulture classes at Western Illinois University in Macomb, Illinois. She earned both her bachelor's degree in Agronomy and her master's degree in Plant Genetics at The University of Arizona. Her master's research project was concerned with germination problems associated with triploid seeds, from which seedless watermelons grow. Following that she worked for 5 years in a breeding and research program for Sunworld, International near Bakersfield, California. She worked with peaches, nectarines, plums, apricots, and cherries. Then she returned to school to earn her Ph.D. in Horticultural Genetics at The Pennsylvania State University. Her Ph.D. research focused on flowering processes in regal pelargonium (also called Martha Washington geraniums). While at The Pennsylvania State University, she bred a new cultivar of regal pelargonium, "Camelot." At Western Illinois University, Dr. Loehrlein teaches nine courses: Greenhouse and Nursery Management, Introductory Horticulture, Landscape Design, Landscape Management, Home Horticulture, Plant Propagation, Turf Management, and two courses in Plant Identification.
TABLE 15-1
Turfgrass Species and Their Qualities

NAME                  SPECIES                 SEASON

Bermudagrass          Cynodon spp.            Warm

Bluegrass             Poa pratensis           Cool, transitional

Buffalograss          Buchloe dactyloides     Warm

Creeping              Agrostis palustris      Cool
  bentgrass

Fine fescue           Festuca rubra spp.      Cool

Perennial             Lolium perenne          Cool
  ryegrass

St. Augustinegrass    Stenotaphrum            Subtropical, warm
                        secundatum

Tall fescue           Festuca arundinacea     Cool, transitional

Zoysia                Zoysia spp.             Warm,
                                                transitional

                      SPREADING               WEAR
NAME                  HABIT                   RESISTANCE

Bermudagrass          Stolons and             Excellent
                        rhizomes

Bluegrass             Rhizomes                Fair

Buffalograss          Stolons                 Poor

Creeping              Stolons                 Poor
  bentgrass

Fine fescue           Tillers, short          Poor to fair
                        rhizomes

Perennial             Tillers                 Fair to good
  ryegrass

St. Augustinegrass    Stolons                 Fair

Tall fescue           Tillers                 Good

Zoysia                Stolons and             Excellent
                        rhizomes

NAME                  RECUPERABILITY

Bermudagrass          Excellent

Bluegrass             Good

Buffalograss          Slow

Creeping              Very good
  bentgrass

Fine fescue           Poor to fair

Perennial             Poor to fair
  ryegrass

St. Augustinegrass    Good

Tall fescue           Poor to fair

Zoysia                Poor

TABLE 15-2
Select Bermudagrass Cultivars

NAME          IMPROVED QUALITIES

Princess      High-quality, fine texture

Savannah      High-quality

Sundance      High-quality

Tifsport      Superior cold tolerance

Tifway        High-density, fine-textured, wear-resistant

Tifway II     Similar to Tifway, but with improved frost and nematode
                tolerance

TABLE 15-2
Select Bermudagrass Cultivars

NAME          IMPROVED QUALITIES

Princess      High-quality, fine texture

Savannah      High-quality

Sundance      High-quality

Tifsport      Superior cold tolerance

Tifway        High-density, fine-textured, wear-resistant

Tifway II     Similar to Tifway, but with improved frost and nematode
                tolerance

TABLE 15-3

Cultivars of Select Bluegrass Species

NAME              IMPROVED QUALITIES

Adelphi           Tolerance to diseases, heat tolerance,
                    rapid establishment

Blue Bonnet       Low maintenance, withstands stress

Blue Star         Stress and disease resistant; low
                    maintenance

Eclipse           Moderate shade tolerance, heat
                    tolerance, tolerance to diseases

Glade             Moderate shade tolerance, rapid
                    establishment

Midnight          Tolerance to diseases, heat tolerance,
                    aggressive growth, rapid
                    establishment

Touchdown         Tolerance to diseases, aggressive
                    growth

TABLE 15-4

Mixes and Blends of Turf

MIX OR BLEND                RECOMMENDED USE

Annual and/or               Bare spot repair, quick-
  perennial ryegrass          establishing turf that
                              overseeds readily

Bluegrass, perennial        All-purpose/sun and shade
  rye, and fine fescues

Bluegrasses                 High-quality turf with
                              complementary disease
                              and stress tolerance

Fine fescues                Shady areas

Kentucky bluegrass,         Sunny areas with one fast and
  perennial ryegrass          one slower to establish,
                              complementary texture and
                              color, different disease and
                              stress resistance

Perennial ryegrass          Medium- to high-quality turf
                              that establishes quickly

TABLE 15-5

Seeding Rates of Common Turfgrass Species

SPECIES                         SEEDING RATE
                                (lb/1,000 sq ft)

Bermudagrass (Cynodon spp.)     1-2

Zoysia (Zoysia spp.)            1-3

Buffalograss (Buchloe           5-12
dactyloides)

Tall fescue (Festuca            6-9
arundinacea)

Bluegrass (Poa pratensis)       1-2

Perennial ryegrass              6-9
(Lolium perenne)

Fine fescue (Festuca rubra      3-5
subspecies)

Creeping bentgrass              0.5-1.5
(Agrostis palustris)

TABLE 15-6
Mowing Heights of Common Turfgrass Species

SPECIES                              MOWING HEIGHT (in.)

Bentgrass                            0.2-0.5

Bermudagrass                         0.5-1.0

Buffalograss, fine                   1.0-2.0
  fescue, Kentucky bluegrass,
  perennial ryegrass

Tall fescue, St. Augustinegrass      1.5-3.0

TABLE 15-7

Problem Spots and Their Weeds

PROBLEM             WEEDS                      ACTION

Wet                 Annual bluegrass,          Improve drainage;
                      nutsedge, moss,            reduce irrigation
                      ruches

Compacted           Annual bluegrass,          Core cultivation
                      broadleaf plantain,
                      prostrate spurge,
                      knotweed, goosegrass,
                      corn speedwell

Low nitrogen        Clover, common             Increase nitrogen
                      speedwell,                 application
                      birdsfoot trefoil,
                      hawkweed

Shady               Creeping Charlie           Plant shade-tolerant
                                                 turf species or
                                                 groundcovers

Droughty            Yellow woodsorrel,         Increase irrigation
                      black medic,
                      prostrate spurge,
                      birdsfoot trefoil,
                      goosefoot

Mowing too close    Annual bluegrass,          Raise mowing height
                      chickweeds, moss,
                      speedwells

TABLE 15-8
Types of Weeds Found in Turf

WEED                SPECIES                  ANNUAL

Annual bluegrass    Poa annua                  X

Crabgrass           Digitaria spp.             X

Goosegrass          Eleusine indica            X

Nutsedge            Cyperus spp.

Wild garlic         Allium canadense

Common chickweed    Stellaria media            X

Clover              Trifolium repens

Cranesbill          Erodium cicutarium

Creeping Charlie,   Glechoma hederacea
  ground ivy

Dandelion           Taraxicum officinale

Henbit              Lamium amplexicaule        X

Knotweed            Polygonum spp.

Mallow              Malva spp.                 X

Black medic         Medicago lupinula          X

Plantain            Plantago spp.

Speedwells          Veronica spp.              X

Violet              Viola papilionacea

Woodsorrel          Oxalis spp.                X

WEED                     PERENNIAL          MONOCOT      DICOT

Annual bluegrass                               X

Crabgrass                                      X

Goosegrass                                     X

Nutsedge                     X                 X

Wild garlic                  X                 X

Common chickweed                                           X

Clover                       X                             X

Cranesbill                   X                             X

Creeping Charlie,            X                             X
  ground ivy

Dandelion                    X                             X

Henbit                                                     X

Knotweed                     X

Mallow                                                     X

Black medic             X sometimes                        X

Plantain                     X                             X

Speedwells                                                 X

Violet                       X                             X

Woodsorrel                                                 X

TABLE 15-9
Alternatives to Turf for Difficult Areas

COMMON           BOTANICAL
NAME             NAME                      SUN/SHADE

Bugle weed,      Ajuga reptans             Shade to sun
  Ajuga

Chamomile        Anthemis                  Sun to partial
                   nobilis                   shade

Dichondra        Dichondra                 Sun to partial
                   micrantha                 shade

English ivy      Hedera helix              Sun or shade

Vinca,           Vinca major               Sun or shade
  periwinkle

Vinca, lesser    Vinca minor               Shade
  periwinkle,
  creeping
  myrtle

COMMON                                     USDA
NAME             OTHER                     ZONE

Bugle weed,      May spread into           3-9
Ajuga              surrounding turf
                   areas; cultivars in
                   bronze to purple
                   leaves

Chamomile        Finely textured leaves    5-9
                   and small yellow
                   flowers fragrant

Dichondra        Slope                     9-11

English ivy      Slope. May be             4-9
                   invasive.

Vinca,           Grows profusely in        7-9
  periwinkle       summer, may be
                   deciduous in
                   colder zones, but
                   spreads
                   increasingly each
                   year

Vinca, lesser    Slope                     4-8
  periwinkle,
  creeping
  myrtle
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Author:Loehrlein, Marietta M.
Publication:Home Horticulture: Principles and Practices
Date:Jan 1, 2008
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