Mowing has a measurable effect on the way a grass plant grows. The ability of a grass to sustain itself through frequent close clipping is one factor that distinguishes a grass species as a turfgrass. Grasses such as wheat, corn and oats cannot tolerate the harsh treatment of frequent mowing. How often should a turf be mowed? The rate of growth and the height of cut determine the frequency of mowing. The rate of growth depends on the type of grass, soil fertility (especially nitrogen content) and the weather. Lawns in Louisiana are warm-season grasses. These grasses grow faster and need to be mowed more frequently in the hot summer if moisture is adequate. A general rule is to mow before the grass becomes one and a half times as tall as the cutting height of your mower. Or another way to say this is: Do not remove more than one-third of the grass top at any one clipping. For example, if the height of cut is 1 inch, mow when growth reaches 1½ inches in height. If you continually allow your grass to grow too tall between mowings, a thin, weedy turf may develop. You can decrease the frequency of mowing by:(1) choosing a slower growing turf grass, (2) reducing the rate of nitrogen fertilization and (3) raising the cutting height of your mower. The rate of nitrogen fertilization and the frequency and height of cut are major factors that determine the quality of turf. Mowing height depends on the type of grass, your objectives and your willingness to work. Table 1 shows the recommended range of cutting heights for different grasses. You can achieve a better quality turf at the lower heights, but you will need to mow more frequently, have a more level terrain and need to apply a higher rate of nitrogen fertilization. Most people now mow with rotary mowers. These mowers have horizontal blades that flail the grass and fray the leaf blades. A rotary mower becomes noticeably duller after a few cuts and should be sharpened as needed. Some tough grasses like the zoysia will dull a blade quickly. Reel mowers have clean, scissorlike cuts and produce a better quality turf than do rotary mowers. A reel mower is more difficult to sharpen, but it should require less frequent sharpening. A reel mower may be more expensive, but it is normally more rugged and uses less fuel. Most reel mowers are particularly recommended for bermuda and zoysia grasses. A smooth turf, free of sticks, stone and other debris, is necessary when using a reel mower. Removal of turfgrass clippings is not necessary if you mow as recommended. Research has shown that moderate amounts of small clippings decompose rapidly in warm weather with good moisture. Nutrients in the clippings are recycled with out contributing greatly to the thatch layer. Nitrogen fertilization can be reduced if clippings are not removed. Clippings should be removed if they form clumps on the surface. Clumping normally occurs only if the grass is allowed to grow too high before mowing or if mowed when wet. Zoysia and centipede leaves do not decay as readily as leaves of other grasses, so clippings need to be collected and discarded when growth is rapid – especially with zoysia.

Watering

To maintain a healthy green lawn, the grass must have a continuous supply of water. When drought comes, grass stops growing and may enter a dormant state. Such advanced dormancy is characterized by death of the leaves and a resting state of the growing points. These growing points are found in the crowns, stolons and rhizomes of the turfgrass. When soil moisture levels are increased to favorable levels by rain or by irrigation, the growing points start the growth of new leaves and stems. Of course, brown turf caused by drought is not desirable, but it is some consolation to know that grass can usually survive without irrigation. You can avoid dormancy and discoloration by irrigating as needed. If done improperly, however, irrigation can create problems. In general, 1 or 2 inches of water are needed per week in times of drought to keep turfgrasses actively growing. Use sprinklers that provide uniform coverage.

Reel Mower

During dry periods, water established lawns only once or twice a week with at least 1 inch of water each time. Light, frequent waterings wet only the surface of the soil and may result in shallow roots and a weak turf. The best time to water is in the morning. It is safest, from a disease standpoint, not to keep a grass wet all night long. Contrary to popular belief, watering during the day will not ‘scald’ turfgrass. The shallow-rooted centipedegrass is very responsive to irrigation when conditions are dry.

Thatch Control

Thatch is a layer of living and dead grass plant parts and clippings located between the soil surface and the green vegetation. Thatch is normally a problem only on zoysia, but St. Augustine, centipede and Bermuda do develop serious problems if not on some thatch control program. A thin layer of thatch is desirable because it insulates the soil, cushions the crowns of the grass from damage caused by foot traffic and reduces water loss from the soil; however, thatch may accumulate faster than it decomposes when lawns are overfertilized, overwatered, mowed too infrequently or mowed too high. Excessive thatch (over 3/4 of an inch) creates many problems. Turf plants begin growing in the thatch instead of the soil. Insects and diseases thrive in the thatch environment. Water and fertilizer cannot move well through the thatch. The puffiness of the thatch can cause the mower to sink into the thatch layer and scalp off the grass. Excessive thatch may increase winter damage and drought susceptibility, too. The rate of thatch accumulation can be decreased and controlled by lowering the fertility rate, watering properly and by following correct mowing practices. By applying an annual light topdressing of soil or sand 1/4 inch thick, you can reduce thatch problems. At this rate, you will need 3/4 cu. yd of soil to topdress 1,000 sq. ft. When the thatch layer exceeds 3/4 of an inch, dethatching is in order. You can remove thatch by using a specially designed hand rake, power rakes, vertical mowers and core aerifiers. This equipment, with exception of core aerifiers, may be rented from most rental stores.The core aerifier punches small holes through the thatch and into the soil. It deposits these soil cores on the turf surface. This soil can be incorporated back into the turf by raking and is desirable since soil helps in thatch degradation. The holes created by aerification allow immediate penetration of fertilizer, water and air — all of which also contribute to thatch decay. In heavy and compacted soils, sand may be spread and washed into these holes to reduce future compaction. Core aerification can be contracted through some lawn care services.