Chapter 27 Care of the lawn.
Upon completion of this chapter, you should be able to
* describe the operations needed to repair a lawn in the spring season
* explain the meaning of fertilizer analysis statements
* determine the amount of fertilizer needed to cover a specific area of lawn
* compare revolving, oscillating, and automatic sprinklers
* compare reel, rotary, and flail mowers
* explain the ways lawns can be damaged
Of all aspects of the landscape that require maintenance during the year, lawns consume the most time. A lawn necessitates both seasonal care and weekly care. Like any other feature of the landscape, it is easier to maintain if it is installed properly. Thus, the landscaper who is hired to install and maintain a lawn may have an easier job than the landscaper hired to maintain a lawn that was poorly installed by someone else.
Spring Lawn Care
Spring operations begin the season of maintenance. In areas of the country where winters are long and hard, lawns may be covered with compacted leaves, litter, or semi-decomposed thatch. The receding winter may leave behind grass damaged by salt injury, disease, or freezing and thawing.
Small areas can be cleaned of debris with a strong rake. Larger areas of several acres or more require the use of such equipment as power sweepers and thatch removers to accomplish the same type of cleanup.
Rolling of the Lawn
In many central and northern states, the ground freezes and thaws many times during the winter. Such action can cause heaving of the turfgrass. Heaving pulls the grass roots away from the soil, leaving them exposed to the drying wind. Heaving also creates a lumpy lawn.
Where heaving occurs, it is advisable to give the lawn a light rolling with a lawn roller in the spring. Rolling presses the heaved turf back in contact with the soil. The roller is applied in a single direction across the lawn, followed by a second rolling at an angle perpendicular to the first.
Two precautions should be observed before rolling a lawn. One is that clay soil should never be rolled, since air can be easily driven from a clay soil and the surface quickly compacted. The other precaution is that no soil should be rolled while wet. The roller can be safely used only after the soil has dried and regained its firmness.
The First Cutting
The first cutting of the lawn each spring removes more grass than the cuttings that follow later in the summer. The initial cutting at 1 1/4 to 1 1/2 inches is done to promote horizontal spreading of the grass. This, in turn, hastens the thickening of the lawn. An additional benefit of the short first cutting is that fertilizer, grass seed, and weed killer that are applied to the lawn reach the soil's surface more easily. Cuttings done later in the year are usually not as short.
Patching the Lawn
If patches of turf have been killed by diseases, insects, dogs, or other causes, it may be necessary to reseed them or add new sod, plugs, or sprigs. Widespread thinness of the grass does not indicate a need for patching. It indicates a lack of fertilization, improper mowing, disease, or insects.
Patching is warranted when bare spots are at least 1 foot in diameter. Seed, sod, plugs, or sprigs should be selected to match the grasses of the established lawn. Plugs can be set directly into the soil using a bulb planter or golf green cup cutter to cut the plug, and then to remove the soil where it is to be planted. With seed, sod, and sprigs, it is best to break the soil surface first with a toothed rake. A mixture of a pound of seed in a bushel of topsoil is handy for patching where seed is to be used, Figure 27-1. Mulch and moisture must then be applied, as stated earlier.
The timetable for patching is the same as for planting and is related to the type of grass involved.
Aeration of a lawn is the addition of air to the soil. The presence of air in the soil is essential to good plant growth. If the lawn is installed properly, the incorporation of sand and organic material into the soil promotes proper aeration. However, where traffic is heavy or the clay content is high, the soil may become compacted. The groundskeeper can relieve the compaction by use of a power aerator, Figure 27-2. There are several types of aerators. All cut into the soil to a depth of about 3 inches and remove plugs of soil or slice it into thin strips.
A topdressing of organic material is then applied to the lawn and a rotary power mower run over it. This forces the organic material into the holes or slits left by the aerator. The plugs of soil left on top of the lawn may be removed by raking. If the soil plugs are not too compacted, they can be broken apart and left as topdressing. Equipment is made that can aerate and convert the soil plugs to topdressing in a single operation.
[FIGURE 27-1 OMITTED]
[FIGURE 27-2 OMITTED]
Vertical mowing is a technique that can break up the soil plugs left by an aerator or even remove excessive thatch if necessary. It requires a power rake or a mower whose blades strike the turf vertically. It is done when the lawn is growing most rapidly and conditions for continued growth are favorable. For cool-season grasses, late summer or early autumn is the best time. For warm-season grasses, late spring to early summer is best.
The blades of the vertical mower are adjusted to different heights depending upon the objectives of the operator. A high setting is used to break up soil plugs. A lower setting gives deeper penetration into the thatch layer. This makes it easier to remove and relieves compaction of the soil. Deep vertical mowing is only practiced on deep-rooted turfs. Shallow-rooted turfs often grow mainly in the thatch layer. They can be harmed more than helped by vertical mowing.
Following a mowing, the cut clippings can be either collected or left on the lawn. While it may seem to be a matter of personal preference, in fact there is a reason to do it a certain way at certain times. It all has to do with the length of the clippings. The clippings contain nutrients that can be used by the grass plants once the clippings decompose and return those nutrients to the soil. Short clippings of healthy turf that result from regular, frequent mowing during the summer decompose rapidly and should not be collected. However, when the clippings are long, they can be problematic. Clumps of dead clippings on the lawn's surface are unattractive. Further, they will not decompose as quickly and may impair the growth of the grass beneath them by reducing the amount of light, retaining excessive moisture that may promote disease, or just smothering the grass. In such situations, the clippings should be collected as the lawn is mowed.
Much like grass seed, lawn fertilizer is sold in an assortment of sizes and formulations and priced accordingly. Stores selling fertilizers range from garden centers to supermarkets. The professional groundskeeper needs to have a basic knowledge of fertilizer products prior to their purchase. Otherwise, it is difficult to choose among the many brands available.
Nutrient Analysis and Ratio
The fertilizer bag identifies its contents. It displays three numbers that indicate its analysis, that is, the proportion in which each of three standard ingredients is present. These numbers, such as 10-6-4 or 5-10-10, indicate the percentage of total nitrogen, available phosphoric acid, and water-soluble potash present in the fertilizer, Figure 27-3. The numbers are always given in the same order and always represent the same nutrients.
With simple arithmetic, fertilizers can be compared on the basis of their nutrient ratios. For example, a 5-10-10 analysis has a ratio of 1-2-2. (Each of the numbers has been reduced by dividing by a common factor, in this case 5.) A fertilizer analysis of 10-20-20 also has a ratio of 1-2-2. As the example in the following column illustrates, a 5-10-10 fertilizer supplies the three major nutrients in the same proportion as a 10-20-20 fertilizer, but twice as much of the actual product must be applied to obtain the same amount of nutrients as is contained in the 10-20-20 fertilizer.
50 pounds of 5-10-10 50 pounds of 10-20-20 fertilizer contain: fertilizer contain: 2 1/2 pounds of N 5 pounds of N (nitrogen) 5 pounds of [P.sub.2][O.sub.5] 10 pounds of [P.sub.2][O.sub.5] (phosphoric acid) 5 pounds of [K.sub.2]O 10 pounds of [K.sub.2]O (potash)
The ratio of the fertilizers is the same, but the amount of nutrients available in a bag of each differs. The 5-10-10 mixtures should be less expensive than the higher analysis material.
Thus, one measure of the quality of a fertilizer is its analysis. The higher the analysis, the greater is the cost. Whether or not a high analysis fertilizer is needed depends upon the individual plant. Generally, residential lawns do not need a high analysis fertilizer.
In addition to the three major nutrients, fertilizers may contain additional trace elements. These nutrients are essential for plant growth but needed in very small amounts. Most soils are not deficient in trace elements, so their presence in a fertilizer product may be more coincidental than intentional. In those regions of the country where a particular trace element is either deficient or unavailable to the plant because it is bound too tightly within the soil, then its inclusion in the fertilizer is important.
[FIGURE 27-3 OMITTED]
Forms of Nitrogen Content
Another factor influencing the quality and cost of fertilizers is the form of nitrogen they contain. Some fertilizers contain nitrogen in an organic form. Examples include peat moss, peanut hulls, dried blood, tobacco stems, sewage sludge, and cottonseed meal. The nitrogen content of these materials ranges from 1 1/2 to 12 percent, depending upon the particular material. While sewage sludge is used to some extent on golf course turf, organic fertilizers are not widely used for fertilization of grasses because they are too low in nitrogen. Often, the nitrogen present is not in a form that can be used by plants. The best use of organic fertilizers is as soil conditioners that greatly improve the water retention and aeration of the soil.
Chemical forms are the most commonly used fertilizers. They contain a higher percentage of nitrogen. The nitrogen may be quickly available or slowly available; this determines the timing of the nitrogen's release into the soil and uptake by the grass or other plants. It also influences the cost of the fertilizer.
Quickly available fertilizers usually contain water-soluble forms of nitrogen. This means that the nitrogen can be leached (washed) through the soil before the plants take it in through their root systems. Slowly available fertilizers (also called slow-release) make their nitrogen available to the plant more gradually and over a longer period of time. The slow-release effect is possible because the nitrogen used is in a form that is insoluble in water. This gives the plants more time to absorb the nitrogen and prevents fertilizer burn of the plant. Slow-release fertilizers are therefore more expensive than the quickly available forms. Slow-release fertilizers are usually labeled as such. This helps the landscaper to know what is being purchased and what to expect as a response from the plants.
A final factor affecting the price and quality of a fertilizer is the amount of filler material it contains. This is directly related to the analysis of the product. Filler material is used to dilute and mix the fertilizer. Certain fillers also improve the physical condition of mixtures. However, filler material adds weight and bulk to the fertilizer, thereby requiring more storage space.
The following listing compares high analysis fertilizers (those with a high percentage of major nutrients) and low analysis fertilizers (those with a low percentage of major nutrients) on various plants.
In summary, fertilizer cost is determined by three major factors: analysis, form of nitrogen, and amount of bulk filler material. The higher the analysis and the greater the percentage of slow-release nitrogen, the more expensive is the fertilizer.
High Analysis Low Analysis Fertilizer Fertilizer Contains more nutrients Contains fewer nutrients and less filler and more filler Cost per pound of Cost per pound of actual nutrients is actual nutrients is less greater Weighs less; less labor Is bulky and heavy; more is required in labor is required in handling handling Requires less storage Requires more storage space space Requires less material Requires more material to provide a given to provide a given amount of nutrients amount of nutrients per square foot per square foot Requires less time to Requires more time to apply a given amount apply a given amount of nutrients of nutrients
When to Fertilize Lawns
Lawns should be fertilized before they need the nutrients for their best growth. Cool-season grasses derive little benefit from fertilizer applied at the beginning of the hot summer months; only the weeds benefit from nutrients applied during the late spring. Cool-season grasses should be fertilized in the early spring and early fall. This supplies proper nutrition prior to the seasons of greatest growth. Landscapers should never practice late fall fertilization--it encourages soft, lush growth, which is damaged severely during the winter.
Warm-season grasses should receive their heaviest fertilization in late spring. Their season of greatest growth is the summer.
Amount of Fertilizer
The amount of fertilizer to use is usually stated in terms of the number of pounds of nitrogen to apply per 1,000 square feet. The number of pounds of nitrogen in a fertilizer is determined by multiplying the weight of the fertilizer by the percentage of nitrogen it contains.
How many pounds of actual nitrogen are contained in a 100-pound bag of 20-10-5 fertilizer?
100 pounds x 20% N = pounds of N
100 x 0.20 = 20 pounds of N
How many pounds of 20-10-5 fertilizer should be purchased to apply 4 pounds of actual nitrogen to 1,000 square feet of lawn?
Divide the percentage of N into the pounds of N desired. The result is the number of pounds of fertilizer required.
4 pounds of N desired
/ 20% = pounds of fertilizer required
4 / 0.20 = 20 pounds of 20-10-5 fertilizer required
"A Comparison Chart for Turfgrasses" in Chapter 21 lists general fertilizer recommendations for various grasses.
When applying fertilizer to lawns, the recommended poundage should be divided into two or three applications. For example, the 4 pounds of nitrogen per 1,000 square feet for bluegrasses and fescues might be applied at the rate of 2 pounds in the early spring and 2 pounds in the early fall. Another possibility is to apply 1 pound in early spring, 1 pound in midsummer, and 2 pounds in early fall. A spreader must be used to assure even distribution of the fertilizer. It is applied in two directions with the rows slightly overlapped, Figure 27-4.
Watering the Lawn
Turfgrasses are among the first plants to show the effects of lack of water, since they are naturally shallow rooted compared to trees or shrubs. The groundskeeper should encourage deep root growth by watering so that moisture penetrates to a depth of 8 to 12 inches into the soil. Failure to apply enough water so that it filters deeply into the soil promotes shallow root growth, Figure 27-5. Such shallow root systems can be severely injured during hot, dry summer weather.
Infrequent, deep watering is much preferable to daily, shallow watering. The quantity of water applied during an irrigation will depend upon the time of day and the type of soil. Clay soils allow slower water infiltration than coarser textured sandy soils, but clay soils retain water longer. Therefore, less water may need to be applied to clay soils, or the rate of application may need to be slower, or both. The amount of water given off by a portable sprinkler can be calibrated once and a notation made for future reference. To calibrate a portable sprinkler, set several wide-topped, flat-bottomed cans with straight sides (such as coffee cans) in a straight line out from the sprinkler. When most of them contain 1 to 1 1/2 inches of water, shut off the sprinkler. The amount of time required should be noted for future use. Figures 27-6 and 27-7 illustrate two types of portable sprinklers. In addition, permanently installed irrigation systems are available (at considerable cost) for large turf plantings, Figure 27-8.
[FIGURE 27-4 OMITTED]
[FIGURE 27-5 OMITTED]
The best time of day to water lawns is between early morning and late afternoon. Watering in the early evening or later should be avoided because of the danger of disease; turf diseases thrive in lawns that remain wet into the evening. Watering prior to evening gives the lawn time to dry before the sun sets.
If watering is done at the proper time and to the proper depth, it is necessary only once or twice each week.
[FIGURE 27-6 OMITTED]
Mowing the Lawn
Three types of mowers are available for the maintenance of lawns: the reel mower, the rotary mower, and the flail mower. The flail mower is used for turfgrasses that are only cut a few times each year. Reel and rotary mowers are used to maintain home, recreational, and commercial lawns. On a reel mower, the blades rotate in the same direction as the wheels and cut the grass by pushing it against a nonrotating bedknife at the rear base of the mower, Figures 27-9 and 27-10. The blades of a rotary mower move like a ceiling fan, parallel to the surface of the lawn, cutting the grass off as they revolve, Figure 27-11. Reel mowers are most often used for grasses that do best with a shorter cut, such as bent-grass. Rotary mowers do not cut as evenly or sharply as reel mowers. However, they are satisfactory for lawn grasses that accept a higher cut, such as ryegrass, bluegrass, and fescue. The riding mower, so popular with homeowners, is a rotary mower. Many campuses, parks, and golf course fairways are mown with a large bank of reel mowers, called a gang mower. It is pulled behind a tractor that has been fitted with tires that will not rut the lawn.
In every situation, the blades must be sharp to give a satisfactory cut. Dull or chipped mower blades can result in torn, ragged grass blades that will die and give the lawn an unhealthy color of grey or brown. The sharp blades of any lawn mower should be respected. When powered, they can cut through nearly any shoe. Workers should never mow unless wearing steel-toed work shoes. Hands should never be near the blades while the mower is running. No inconvenience caused by shutting off a mower can equal the instant injury that a power mower can cause to a worker's hand or foot.
[FIGURE 27-7 OMITTED]
[FIGURE 27-8 OMITTED]
[FIGURE 27-9 OMITTED]
[FIGURE 27-10 OMITTED]
"A Comparison Chart for Turfgrasses" in Chapter 21 illustrates the wide range of tolerable mowing heights that exists between and within species. Within the range, the mowing height selected often depends upon how much care the lawn can be given and what surface quality is expected. Shorter heights require more frequent mowing and watering, and, often, greater pest control efforts. In turn, shorter heights give greater density and finer texture to a lawn. A taller lawn surface will have a slightly coarser texture and take longer to thicken. However, it will not require cutting as often. Longer cutting heights will also withstand hot and dry periods better, since the extra blade length will cast cooling shadows over the soil's surface. Often, fewer weeds are an added benefit of a taller lawn surface. Since not all species are mowed to the same height, mixed-species lawns should be made up of grasses that have similar cutting requirements.
[FIGURE 27-11 OMITTED]
The frequency of mowing is variable. Because the rate of growth of a lawn can vary with the temperature and with the moisture provided, the frequency of the mowing cannot always be precisely specified. Ideally, a lawn should be mown when it is needed, not because a contract specifies cutting on a certain day.
A long-standing rule of thumb is that mowing should remove about one-third of the length of the grass blade. Thus, if the turf is being kept at 1 1/2 inches, it should be mowed when it reaches a height of 2 1/4 inches. If the grass gets too long before cutting, the dead clippings can mar the appearance of the lawn. Then as described earlier, the only alternative is to collect the clippings either in a grass-catcher or with a lawn sweeper or rake. If the grass is cut properly, the clippings will not be excessive. They will decompose rapidly and will not require collection.
The pattern of mowing should be varied regularly to prevent wheel lines from developing in the lawn. Varying the pattern also encourages horizontal growth of the shoots. An easy variation is to mow at a 90-degree angle to the last mowing. If done on the same day with a reel mower, an attractive checkerboard pattern develops. The pattern is not so apparent if done with a rotary mower, but the practice is just as healthy for the lawn.
Damage to Lawns
Like all plants, turfgrasses are susceptible to assorted injuries. Damage can be visual or physical and frequently is both. Causes of lawn injury include:
* Thatch build-up
Weeds and Pests
Weeds and pests were described and discussed in detail in Chapter 26. The injuries that they bring to lawns are varied. Weeds usually impact the aesthetic appearance of a lawn. A broad-leaved weed, such as a dandelion, growing within a lawn of fine textured turf grass will not be welcomed. Even coarse textured grasses, such as crabgrass, growing in a lawn of fine textured turf will be unsightly. Since a well-maintained, healthy lawn can discourage the establishment of many weeds, a lawn with a large weed population often indicates additional problems, such as poor soil conditions.
Good landscaping practices are the best defenses against weeds. However, the need for an herbicide is probable in most lawns where appearance of the turf is given a high level of importance. Turf herbicides are available in both liquid and powdered formulations. Some products mix herbicides with fertilizers creating a "weed and feed" product that saves time and labor in its application.
If an herbicide is applied in liquid form, the sprayer should be cleaned afterward and set aside to be used exclusively for that purpose in the future. Small amounts of herbicide remaining in a sprayer can kill valuable ornamental plants if the sprayer is later used to apply another liquid material.
Insect and disease injuries to turf increase in frequency and severity proportionate to the declining health of the lawn. Healthy lawns have fewer insect and disease problems than weak lawns. Because of their comparatively shallow root systems, turf grasses are affected more immediately by environmental conditions and are more immediately responsive to cultural modifications than other landscape plants. Insect damage and diseases can seem to develop overnight if there is a sudden change in the lawn's growing regimen, such as excessive rainfall or a late spring snowfall. The following table, "Common Turf Problems," contains a partial list of the pests and problems that can injure an ordinary lawn.
The best defense against most pest injury is the selection of resistant varieties and the creation of a growth environment that favors the grass more than the pest. For example, watering at night promotes the growth of many fungi that cause turf diseases. Irrigation of lawns should be done earlier in the day, allowing the grass to dry before nightfall. Another example: allowing a thick thatch layer to develop provides a good habitat for certain harmful insects. (Thatch is discussed in the next section.) Large populations of insects in the soil can attract rodents, such as moles, that burrow through the soil to feed on them. So in addition to the injuries caused by the insects, there is additional damage done by the animals that dig after them. Solving the insect problem can indirectly solve the other.
When grass clippings and other plant tissue on the surface of the lawn do not decompose as rapidly as the growth of new tissue occurs, a matted build-up, termed thatch, begins to accumulate. If the layer of thatch is thin, 1/2 inch or less, it can be of benefit to the lawn, serving as a mulch for the grass. As such, it keeps the soil cooler and aids in the retention of moisture. When the thatch becomes too thick, problems begin to occur. Then it begins to harbor insects and pathogenic inoculum. It can also create a cushion over the soil's surface that will permit the wheels of a mower to sink enough to change the mowing height of the lawn.
The best approach to controlling thatch buildup is to prevent it at the outset. The turf should not be allowed to get too high between mowings. If it does occur, the clippings should be collected rather than allowed to remain on the lawn. Dethatching is the term used to describe the intentional removal of the thatch layer. It can be done in different ways depending upon the size of the lawn and the type of landscape site. Small lawns can be dethatched using a steel rake to pull the matted layer away from the soil where it can be collected. That technique is impractical on larger lawns. As mentioned earlier, a vertical mower can be used to slice through the thatch and thereby promote better aeration, which in turn can accelerate the decomposition of the thatch. As the segments of thatch are lifted to the lawn's surface, they should be raked or vacuumed away to prevent their settling back to the soil surface.
Periods of severe water shortage can harm a lawn. The grass will turn brown and enter a stage of dormancy (nongrowth). If the drought continues, the entire lawn can be killed. Irrigation is the major defense against drought. In areas of predictable drought (arid regions), tolerant varieties of grasses should be selected at the time of installation. A greater lawn height is also helpful in withstanding periods of drought.
Vandalism is impossible to control if the vandals are determined. Lawns rutted by vehicles are unattractive and are common abuses of residential and recreational landscapes. Locked gates and the strategic placement of trees can sometimes help by making vehicular access difficult for the would-be vandal. Education to increase public awareness of the value of the landscape and the responsibilities of good citizens is the only real solution of vandalism.
A. Define the following terms.
3. fertilizer analysis
4. low analysis fertilizer
5. slow-release fertilizer
B. What does 10-6-4 on a bag of fertilizer mean?
C. Would 10-6-4 fertilizer be considered a high analysis or low analysis product? Why?
D. Of the three fertilizers listed below, which two have the same ratio of nutrients?
E. Why might the prices of two 50-pound bags of fertilizer differ greatly?
F. At what time of the year are warm-season grasses fertilized? Cool-season grasses?
G. How many pounds of actual nitrogen are contained in a 50-pound bag of 12-4-8 fertilizer?
H. How many pounds of 10-10-10 fertilizer should be purchased to fertilize a 2,000 square-foot lawn of bluegrass and fescue if it is applied at the recommended rate?
I. How much water is needed to deeply soak an average lawn?
J. What is the best time of day to water lawns?
K. Describe how to repair a lawn by seeding, sodding, sprigging, and plugging.
L. Match the type of sprinkler with its characteristic:
a. revolving 1. casts water in an arched pattern b. oscillating 2. permanently installed system for large landscapes c. automatic 3. casts water in a circular pattern M. Match the type of mower with its characteristic: a. flail 1. blades move like a ceiling fan, parallel to the lawn's surface b. reel 2. used for grasses that are only cut a few times each year c. rotary 3. the blades rotate in the same direction as the wheels
N. List five different ways that lawns can be damaged.
O. What should be done with the clippings of a lawn that is mowed weekly and why?
1. Study "A Comparison Chart for Turfgrasses" in Chapter 21 and match grasses growing in your local area that could be blended and grown together successfully. Compare grasses on the basis of texture, frequency of fertilization, mowing height, and preferred soil type.
2. Calibrate one or more types of portable sprinklers following the directions given in this chapter. Determine the length of time each requires to apply 1 inch of water and measure the area of coverage.
3. Visit a lawn equipment dealership. Ask the owner to show the various models of mowers, spreaders, sprayers, rollers, and rakes that are stocked for lawn maintenance.
4. Have an equipment field day, perhaps in association with other nearby schools. Invite equipment dealers to bring selected pieces of power equipment to the school for demonstration and/or student use.
5. Measure thatch layers from different types of turf area, such as a well-maintained residential lawn, a public park, a cemetery, an athletic field, a golf green. With a sharp knife, cut down into each turf area and remove a small plug of sufficient size to permit the thatch to be seen and its depth measured. Compare the depth of the thatch with the frequency of mowing and the type of grass.
Jack E. Ingels
State University of New York
College of Agriculture and Technology
Cobleskill, New York
Common Turf Problems Turf Insects Turf Diseases Other Problems * Ants * Anthracnose * Dogs * Army worms * Brown patch * Gophers * Bill bugs * Copper spot * Ground squirrels * Chinch bugs * Dollar spot * Mice * Cut worms * Fairy ring * Moles * Grubs * Fusarium blight * Human vandalism * Leaf hoppers * Leaf spots * Vehicles and * Mites * Net blotch equipment * Mole crickets * Nematodes * Periodical cicadas * Powdery mildew * Scale * Pythium blight * Sod webworm * Red thread * Weevils * Rots * Wireworms * Rusts * Slime molds * Smuts * Snow molds
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|Title Annotation:||SECTION 3 Landscape Maintenance|
|Publication:||Landscaping Principles and Practices, 6th ed.|
|Date:||Jan 1, 2004|
|Previous Article:||Chapter 26 Plant injuries: identification and care.|
|Next Article:||Chapter 28 Winterization of the landscape.|