I am hearing lots of comments about “it being so wet, I can’t get my yard mown”.  This cool, wet spring has been perfect growing weather for our cool season lawns.  When it seems to rain every day, it can become a challenge to keep up with the growth.  So what do you do when the lawn can't be cut because of constant rain?  

The first step is to wait until the grass is dry before you mow.  Trying to cut wet grass will result in the clippings clumping together instead of being evenly distributed across the lawn.  These clumps can cause the grass underneath to die as well as providing a place for diseases, mold and fungi to grow.  It also will collect under the mower deck reducing the quality of the cut as the underside of the mower fills up – and it is a pain to clean!  If the tires of the mower are wet as you mow, the lawn is too wet to cut.

The second step is to set your mower as high as possible and bring the length of the grass down in steps over several mowings.  It is always best never to take more than one third of the grass blade off at one time.  If more is taken, the plant reacts by using stored energy reserves to quickly send up new growth.  This reduces the amount of energy available for the plant to deal with stress or damage done by insects or disease.  However, sometimes it is just not possible to keep the "one-third rule." In such cases, cut as high as possible even though it may mean you are cutting off more than one third of the blade.  Bring the height down gradually by cutting more often and at progressively lower heights until you reach the target height.  It may take 2-3 cuttings before you reach your normal mowing height.

A lawn mown to the correct height will be thicker and healthier resulting in fewer weeds.  What is a good height to keep your grass?  Here is a list of the recommended mowing height ranges (in inches) for home lawns in Missouri:

Tall fescue 3 - 4

Kentucky bluegrass 2-3

Fescue/bluegrass lawns - 3.0 to 3.5 inches.

Bluegrass/ryegrass lawns - 2.5 to 3.5 inches.

Creeping red fescues -3.0 to 3.5 inches   

Buffalograss 2-3

Bermudagrass 2-2.5

Zoysiagrass 2-2.5

There may be some benefits gained by adjusting mowing heights WITHIN the recommended range at times. For example, it is a good practice to mow warm-season grasses at the higher end of recommended heights during late summer and early fall because this practice should help them store more carbohydrate reserves for the winter, and it may reduce the incidence of certain cool-weather diseases. Mowing warm season grasses at the lower end of the range in the spring removes the dead material and speeds the green up of the lawn in the late spring.  But the rule to remember is to stay within the recommended height range for your species.     

Many homeowners believe grass clippings need to be removed to have a healthy, vigorous lawn. By following the steps in the “Don’t Bag It” lawn care program, you can have a beautiful lawn without collecting your grass clippings. See MU Guide 6959 – Don’t Bag It Lawn Care.

Regardless of how high you are mowing, it is important to keep mower blades sharp to cut grass cleanly and evenly.  Dull cutting blades can tear and shred blades of grass and may fail to cut tougher stems and weeds.  These jagged, ripped edges will turn brown as they will not heal as quickly as a cleanly cut blade of grass.  This slower healing and jagged edge can also make it easier for diseases to creep into your lawn.  A sharp blade is critical for a healthy lawn.

Jim Crawford, Natural Resource Engineering Specialist, University of Missouri Extension