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Richard Jauron, Extension Horticulture, (515) 294-1871,
Elaine Edwards, Extension Communication Systems, (515) 294-5168,

Yard and Garden Column for the Week Beginning April 7

Ladies and Gentlemen, Start Your Engines!

By Richard Jauron
Extension horticulturist
Iowa State University Extension

Many gardeners spend considerable time and money to produce a well-groomed, attractive lawn. Fertilizers promote root and shoot growth and produce a dark green color. When necessary, herbicides are used to control crabgrass and broadleaf weeds. While fertilization and weed control are important aspects of lawn maintenance, proper mowing is another vital key. In fact, many turfgrass problems can be traced back to poor mowing practices. 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 is primarily determined by the species of grass and the season. Maintain Kentucky bluegrass lawns at 2 1/2 to 3 inches in the spring and fall months. Set the mower blade to a height of 3 to 3 1/2 inches during summer. The additional leaf area during the summer months shades and cools the crowns of the bluegrass plants. The higher mowing height also provides more food-producing foliage and promotes deeper root growth. The recommended mowing height for tall fescue is 2 1/2 to 3 1/2 inches, while zoysiagrass should be mowed at a height of 1 to 2 inches.

Mowing frequency is based on the growth rate of the turfgrass. The growth rate is largely determined by weather conditions and irrigation and fertilization practices. 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 1/2 inches. In the spring it may be necessary to mow every 4 to 5 days, possibly only once every 1 to 2 weeks in summer, with more frequent mowing again in the fall. Another factor that affects mowing frequency is mowing height. The shorter the grass is mowed, the more often it must be mowed to meet the one-third requirement.

Mowing grass that is much too tall is hard on the mower and, more importantly, injures the grass. The injured turf is less tolerant of environmental stresses, such as heat and drought, and more susceptible to weed infestations. It may take several weeks for the grass to recover from a severe mowing. Another problem is the large amount of clippings. Excessive amounts of clippings are unsightly, tend to smother the turfgrass and create an environment that favors disease development. Grass clippings should be bagged or raked and removed when mowing tall grass.

Mow grass that is extremely tall as soon as possible. Raise the mower blade as high as possible, mow, and 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 mowed properly, the grass clippings do not have to be removed. The small clippings will simply filter down into the turf and decompose quickly, returning essential plant nutrients to the soil. Lawn clippings do not significantly contribute to thatch development.

Mow the lawn with a sharp blade. Sharpen the mower blade each spring. Inspect the blade after each mowing 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.

Because mowers can cause serious injuries to the operator and others, follow safety precautions when mowing the lawn. Dress appropriately, wear sturdy shoes with slip resistant soles and full length pants. Remove all debris including branches, stones and toys from the lawn before mowing. Keep children and pets at a safe distance to protect them from flying debris. Keep hands and feet away from the blade when the mower is running. Never leave the mower running unattended (new models automatically shut off). When using a walk-behind mower, mow across a slope rather than up and down. You are less likely to slip under the mower when mowing across a slope. Always push rather than pull the mower. Proper, careful mowing will help protect the health of the turf and the operator.


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