Mowing the Lawn

Lawns across Iowa have turned a beautiful, dark green in the last few weeks.  Proper mowing practices over the next several months will help keep the lawn attractive and healthy. 

Mowing height and frequency are the most important aspects of mowing.  Mowing height depends upon environmental conditions.  Mow Kentucky bluegrass lawns at a height of 2½ to 3 inches during the cool weather of spring and fall.  Mow Kentucky bluegrass lawns at a height of 3 to 3½ inches in summer (June, July, and August).  A higher mowing height in summer helps to cool the crowns of the turfgrass plants and provides more leaf area for photosynthesis during the stressful warm summer months. 

Mowing frequency is based on the growth rate of the turfgrass.  As a general rule, never remove more than ⅓ of the total leaf surface at any one mowing.  For example, to maintain a lawn at 3 inches, the grass should be mowed when it reaches a height of 4½ inches.  In spring it may be necessary to mow every 4 to 5 days, once every 7 to 10 days may be sufficient in summer, with more frequent mowing again in the fall.  The growth rate of grass (and hence mowing frequency) depends upon cultural practices (such as fertilization and irrigation practices), weather conditions, and other environmental factors. 

Mowing grass that has gotten excessively tall is hard on the mower and, more importantly, is harmful to the grass.  Removing more than one-third of the leaf area weakens the turfgrass, reducing its ability to withstand environmental stresses.  Another problem is the large amount of clippings.  Excessive clippings are unsightly, tend to smother the turfgrass, and create an environment that favors disease development.  Excess clippings may need to be bagged or raked and removed. 

Grass that has grown excessively tall should be mowed as soon as possible.  Raise the mower blade as high as possible, mow, and (if necessary) remove the grass clippings.  Gradually reduce the height of the grass in later mowings until the lawn is being mowed at the proper height. 

When the lawn is properly mowed, grass clippings do not need to be removed or bagged.  Small clippings filter down into the turf and quickly decompose, returning essential plant nutrients to the soil.  Short clippings do not significantly contribute to thatch development.  Mow the lawn with a sharp blade.  Sharpen the mower blade each spring.  Thereafter, periodically inspect the blade and sharpen as needed.  A dull blade tears the ends of the grass blades.  The damaged tissue dries out giving the turf surface a whitish appearance.  Also, the torn leaf tissue losses greater amounts of water and increases the possibility of disease problems. 

Alternate your mowing pattern or direction each time the lawn is mowed.  Repeatedly mowing the lawn in the same direction pushes the grass over rather than cutting it cleanly.  Also, different mowing patterns reduce soil compaction and wear from the mower wheels. 

Whenever possible, mow the lawn when the grass is dry.  Wet grass is more difficult to cut and occasionally clogs rotary mowers.  Also, it's safer to mow the lawn when the grass is dry as there is less risk of slipping and being injured by the mower.

Authors: 

Richard Jauron Extension Program Specialist II

Provide horticultural information to home gardeners and extension staff via the telephone, written communication (Horticulture and Home Pest News, Yard and Garden,  and extension publications), radio, computer (Internet and e-mail), and live presentations.   Also assist with the Master ...

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