Three types of mowers are used to maintain turf plantings: the reel mower, the rotary mower, and the flail mower. The flail mower is used for utility and stabilization 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 13-17 and 13-18). 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 13-19). Reel mowers are most often used for grasses that do best with a shorter cut, such as bentgrass. Rotary mowers do not cut as evenly or sharply

figure 13-19. A rotary mower (Delmar/Cengage Learning)

but are satisfactory for lawn grasses that accept a higher cut such as ryegrass, bluegrass, and fescue. The riding mower, so popular in sub­urbia, is a rotary mower. Many campuses, parks, and golf course fair­ways are mown with a large bank of reel mowers (called a gang mower) pulled behind a tractor that has been fitted with tires that will not rut the lawn.

Recently, pull-behind wide area rotary mowers have found accep­tance as a means to cut a swath up to 22 feet in width per pass. A config­uration of three mower decks linked side by side and connected to the power take-off unit of the towing tractor can mow from 50 to 75 acres of open turf in an eight hour day.

While mower basics have seen little change through the years, the technology and the techniques have been updated recently. Lawn care professionals can select mowers based on the mower deck width, machine weights, horsepower, or styles that include walk-behinds, riding, or even sulky styles that permit the operator to stand and ride behind the mower as though water skiing.

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 gray or brown pallor. 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 brought 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 do to a worker’s hand or foot.

Table 13-1 on page 346, illustrates the often wide range of tolerable mowing heights that exists between and within species. Within the range, the mowing height selected often depends on how much care the lawn can be given and what surface quality is expected. The shorter height will necessitate more frequent mowing, more watering during dry peri­ods, and perhaps greater pest control efforts. In turn, the lawn will respond with greater density and a finer texture due to thinner blades. A taller lawn surface will have a slightly coarser texture (even with grasses classified as fine-leaf forms), take longer to thicken, but need cutting less often. It will also withstand heat 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.

The frequency of mowing is another variable in turfgrass mainte­nance. Because the rate of growth of a lawn can vary with the tempera­ture and with the moisture provided, the frequency of mowing cannot always be precisely specified. Where an inflexible mowing schedule is followed, the turf planting will be unsatisfactory. Nevertheless, profes­sional firms must submit bids for lawn maintenance and so must have a reasonably accurate idea of how many times during the growing season a lawn will require mowing. Estate gardeners and golf course superin­tendents have less of a problem. They can mow when the time is right, not when a contract calls for it.

A long-standing and accepted rule of thumb is that mowing should remove about one-third the length of the grass blade. Thus, if the turf is being kept at one and one-half inches, it should be mowed when it reaches a height of two and one-quarter inches. If the grass is permitted to get too long before cutting, the dead clippings can mar the appear­ance of the lawn. Then the only alternative is to collect the clippings either in a grass-catcher or with a lawn sweeper or rake. If cut properly, the clippings will not be excessive, 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 and to encourage the horizontal growth of the shoots. The easiest variation is to mow at a 90° angle to the previous mowing. If a lawn is mowed in both directions on the same day with a reel mower, an attractive checkerboard pattern develops. The pattern is not so apparent with a rotary mower, but the practice is just as healthful for the lawn.