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 Lawn mowing is more time consuming than any of the other cultural practices involved in caring for a lawn. Regular mowing with a sharp mower blade at the proper height will help keep grass growing vigorously and maintain adequate density to completely cover the soil surface. In addition, mowing with sharp blades will cut the grass blades cleanly rather than tearing and shredding them as would be the case with dull blades. This will cut down on the amount of water lost from the grass plant thereby conserving moisture and reducing the need for additional watering. Shredded ends of the grass blade are more susceptible to disease invasion and can increase the need for fungicides.
The general rules of thumb for mowing lawn grasses are to mow high, mow frequently, and allow the clippings to return to the lawn. Mowing frequency is based entirely on the growth rate of the grass. In spring and fall when grass is growing more vigorously, mowing should be more frequent than during midsummer when growth rates slow. Mow often enough so that no more than 1/3 of the leaf surface of the grass plants is removed at one time. For example, if the finished height is two inches, mow whenever grass reaches three inches in height.
Height of cut plays a very important role in determining the maintenance needs of a lawn. Generally, the higher the height of cut the less the maintenance required. This is primarily due to the fact that higher heights of cut promote deeper root growth into the soil. Shorter heights of cut promote shallower root systems. Deep root systems have naturally greater access to soil water and nutrient reserves thereby increasing their ability to tolerate environmental stresses. Shallower root systems require greater attention to supplementing soil water and nutrient needs to keep the plants healthy and minimize exposure to adverse environmental stress. For most lawn areas, mowing at a height of two to three inches will provide a good quality turf.
In addition to larger and deeper root systems, higher heights of cut restrict the amount of light reaching the soil surface. Since many lawn weed seeds require light for germination, the increased shading from a higher height of cut will actually suppress weed germination and growth thereby cutting down the need for herbicide use or other weed control measures. This can be particularly helpful in controlling our warm season annual grasses such as crabgrass. In turn, this can reduce the dependence on preemergent herbicides for their control. 
Mowing frequency is also increased with shorter heights of cut. For example, if the lawn is maintained at one inch, then only 1/2 inch of growth is needed before mowing is required assuming that no more than 1/3 of the top growth is removed at each mowing. On the other hand, if the height is maintained at 2.5 inches, then about 1 inch of growth could occur before mowing would be required. In general, the more growth needed before mowing is required, the longer the time interval between mowings.
Mowing too infrequently damages the lawn by removing too much of the plant at once. A substantial amount of leaf tissue is removed with infrequent mowing, while proper mowing removes a much smaller portion of leaf tissue. When mowed regularly, clippings filter down into the lawn, decompose rapidly, and recycle nutrients back into the lawn. Continually scalping the turf thinking that the frequency of mowing will be reduced is not only a myth but, can seriously weaken the grass plants inviting unwanted weed invasion and competition.
 Increasing the mowing heights by an inch during midsummer will improve the lawn's ability to tolerate stress caused by heat and drying winds. It is also important to continue mowing throughout the fall until growth stops. The weather is usually warm enough for continued grass growth until early November. Lawns that are too tall at that time frequently mat down during winter, making them more susceptible to winter disease problems such as snow mold and invasion by mice or voles.
Change the direction of mowing each time to promote upright shoot growth. When the lawn is mowed in the same direction every time, the grass may lay down in the direction of mowing. By mowing at right angles every other time, this horizontal growth orientation will be minimized. In addition, the alternate mowing pattern will help prevent continuous scalping of high spots and help prevent soil compaction that may result from repeatedly following the same path.
 Grass clippings will always be a part of lawn care. Because lawns grow at different rates depending on environmental conditions and management practices, it is important to tailor mowing, fertilizing, and watering to meet plant needs, yet avoid excessive growth. Grass clippings an inch or less in length filter down to the soil surface and decompose relatively quickly. Longer clippings have a tendency to remain above the lawn where they appear unsightly and can shade or smother grass beneath. Long clippings need to be removed to avoid both unsightliness and lawn damage.
Bagging clippings did not become commonplace until the 1950s when bagging attachments were designed for rotary motors. In nearly every instance, proper lawn care can greatly reduce or eliminate the need to collect clippings. In fact, clippings are a valuable source of nutrients. University of Minnesota soil test recommendations call for less nitrogen fertilizer if clippings are returned to the lawn. Also, the addition of organic matter in the form of clippings may help to improve the status of your soil if it is sandy or low in organic matter.
Contrary to popular belief, returning clippings to the lawn does not normally contribute to increased thatch formation. Thatch is a layer of undecomposed organic matter that builds up between the soil surface and the actively growing green vegetation. A thatch layer will develop if organic matter is produced faster than it is decomposed by microorganisms. The major factors contributing to thatch development are vigorous grass varieties, excessive nitrogen fertilization, infrequent mowing, and low soil oxygen levels. Small clippings are composed primarily of easily degradable compounds which break down rapidly and do not accumulate. Long clippings may contain wiry stem material that is slow to decompose.
While leaving clippings on the lawn is recommended, certain instances make the practice inadvisable. Following are some exceptions to the rule: · If the lawn is heavily infested with certain leaf diseases, removing clippings may help reduce disease severity. · If the lawn must be mowed when wet, clippings can mat together and smother the grass. · If the grass has become too tall, clippings can mat together and smother the grass. · If your mower is unsafe to operate without a bagging attachment the bag should be left in place.
 When clippings must be collected, using them as mulch in the garden or composting them are two good alternative disposal methods. Grass clippings can provide an effective mulch around garden plants. Mulching helps reduce weeds, conserve moisture, and modify soil temperatures. However, do not apply more than one or two inches of grass clippings as a mulch at one time. Wet grass clippings can mat down and prevent oxygen and moisture from getting down into the soil. When oxygen is limited, anaerobic decomposition of the clippings may take place, leading to the production of offensive odors. Do not use grass clippings as mulch if the lawn was recently treated with an herbicide for dandelions or other broadleaf types of weeds. If clippings are to be used as a mulch, then wait until its been mowed at least twice. Composting involves mixing grass clippings and other plant materials with a small amount of soil containing microorganisms which decompose organic matter. Grass clippings are excellent additions to a compost pile because of their high nitrogen content. However, they should not be the only compost component. As with mulches, a thick layer of grass clippings in a compost pile will lead to bad odors from anaerobic decomposition. Mix them with dry materials such as leaves or straw. Clippings can be composted in the backyard or hauled to municipal composting sites.
 The two principal types of mowers available for use on home lawns include "reel" and "rotary" mowers. Regardless which type is chosen, it is very important to keep the mower blades as sharp as possible. Dull mowers tear grass blades rather than cutting them. This results in injured plants. Reel mowers have a series of revolving blades that cut against a stationary bedknife, much like a scissors. While reel mowers provide the finest quality of cut available, they are expensive, not easily adjusted, and require specialized equipment for sharpening. Also, they can't be used where stones, twigs, or other debris are a problem because of potential damage to the cutting units.
Rotary mowers have a whirling horizontal blade. Rotating blades have the potential for throwing stones or other  small objects in the path of the mower. Therefore, rotary mowers are more dangerous than the reel mowers. They cut the grass by impact, similar to the way a machete works. This causes a rougher, more uneven cut than reel mowers. However, rotary mowers do an acceptable job on virtually any lawn. In addition, they are easier to maintain then reel mowers and can cut taller grass.
Mulching or recycling mowers are now available. A mulching mower recuts grass clippings into smaller pieces and redistributes them uniformly back into the lawn for rapid decay. When the turf is wet, clumping is common with mulching mowers because of the excess water present.
 Modern mowers are equipped with certain safety devices which should not be removed or tampered with. One safety feature is a blade that stops turning when the operator's hands are removed from the controls. Another is a rear-mounted rope pull for starting the mower. This reduces the chance of getting one's foot caught in the blades during starting. Many rotary motors have bagging attachments which affect mower safety. The manufacturer may have a special attachment which is required for safe mowing without a bag. Similarly, discharge chute shields on non-bagging mowers should not be removed.
All mowing equipment should be kept in good working condition. Mowers should be sharpened and adjusted frequently to assure a clean cut. A dull rotary mower frays the ends of grass blades and results in brown tips, which are unsightly and increase the plants' susceptibility to certain plant diseases. Slopes greater than about four to one are both difficult and dangerous to mow. These slopes are good candidates for alternative groundcovers that will stabilize the bank and eliminate the need for routine maintenance such as mowing. Pick up rocks, wires, and sticks before mowing to prevent them from becoming dangerous projectiles. Keep all spectators away from the mower while it is in operation. Young children should not be allowed to operate mowers until they can handle them easily. Use earplugs when operating noisy power mowers. Wear sturdy shoes that protect the feet. Always push the mower forward. Never pull it backward in a motion where a slip will allow your foot under the mower deck. Mow across a slope, not up and down for the same reason. Another safety tip is to delay mowing grass when it is wet. Dry grass is less apt to plug mowers. Footing is better on dry grass, and good footing is important in steep slopes. Finally, there is a growing movement among people with small, easily managed yards, back to "old-fashioned" push-type reel mowers. Newer versions are smaller, lighter-weight, and easier to push than the old clunkers you may have used as a youngster. They have the advantage of quiet, fuel-free operation, and can provide good exercise at the same time. If your property isn't too large, consider these mowers when shopping for a new one.
"Used with permission of University of Minnesota Extension Service"
http://www.extension.umn.edu/topics.html?topic=5
1Hull, R. J., Alm, S. R., and Jackson, N., Toward Sustainable Lawn Turf, in Handbook of Integrated Pest Management for Turf and Ornamentals, Leslie, A.R., Ed., Lewis Publishers, Boca Raton, FL, 1994, chap. 1.
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Mowing Practices
