Yard and Garden: Lawn Mowing Tips

AMES, Iowa — Proper mowing practices play a vital role in helping to maintain a healthy, sustainable home lawn. Horticulturists with Iowa State University Extension and Outreach answer questions about lawns and lawn mowing. Homeowners and gardeners with lawn questions should contact horticulturists at Hortline by emailing hortline@iastate.edu or calling 515-294-3108.

What is the proper mowing height for a lawn? 

Kentucky bluegrass lawns should be mowed at a height of 2.5 to 3 inches in the spring and fall months. Mow bluegrass lawns at a height of 3 to 3.5 inches in June, July and August. A higher mowing height in summer helps to cool the crowns of the turfgrass plants, encourages deeper rooting and provides more leaf area for photosynthesis during the stressful summer months.  

Mowing below the recommended range may scalp the turf and cause the turfgrass to deteriorate. Low mowing heights make the turfgrass more susceptible to drought, high temperature and wear injury. In addition, low mowing heights increase the likelihood of weed problems.  

Mowing too high reduces tillering and causes matting of the grass. Reduced tillering results in fewer and coarser plants. Matted grass creates a micro-environment that encourages disease development.  

How often should I mow my lawn? 

Kentucky bluegrass lawns should be mowed at the height of 2.5 to 3 inches in spring and fall.  Set the mower blade to a height of 3 to 3.5 inches during summer.  

As a general rule, never remove more than one-third 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 4.5 inches.  

Mowing frequency is based on the growth rate of the turfgrass. Weather conditions, cultural practices (such as fertilization and irrigation practices) and other factors determine the growth rate of turfgrass.  

Kentucky bluegrass and other cool-season grasses grow quickly in spring when weather conditions are favorable. The growth of cool-season grasses slows in summer and then picks up again in fall. Fertilizing and irrigating the lawn on a regular basis promote turfgrass growth. In spring it may be necessary to mow every four to five days, possibly only once every one to two weeks in summer, with more frequent mowing again in the fall. 

Should I remove the grass clippings when mowing the lawn? 

When the lawn is mowed properly, 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. Lawn clippings do not significantly contribute to thatch development.  

Grass clippings may need to be bagged or raked and removed when mowing extremely tall grass. You also may want to bag the grass clippings and use them as a mulch in vegetable and flower gardens. 

What are some good mowing practices? 

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.  

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 loses 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. Establish several mowing patterns that result in as few turns as possible. Less turning reduces mowing time and damage to the turf from the turning mower wheels.