Why is My Lawn Turning Brown?

by Jane Martin OSU Extension Agent

In most seasons, June begins a 90-day period of stressful weather for many lawns with rising temperatures and reduced rainfall.  Discovering why a lawn is turning brown is not always easy, and there can be numerous possible causes.  It's best not to jump to a conclusion and simply name the thing that is out there at the moment like grubs or brown patch. 

There are many things to think about, including weather, improper culture, insects, and diseases.  Of course, the following list is a simplified guide and only serves to give you ideas of how to think about possibilities as to why lawns turn brown.

Mowing Injury
Scalping on slopes or on uneven terrain, mowing too short, and filling the mower with fuel on the lawn can cause brown areas. Be aware of slopes and depressions in the lawn and mow accordingly.  Change mowing direction about every other mowing to avoid scalping.   Fill mowers with fuel on driveways or other hard surfaces to avoid spills in the lawn.  In spring, a mowing height of about 2 - 2 1/2" is good for a blue grass - perennial rye mixture. In summer, a mowing height of 3-4" will help keep grass roots shaded and to help keep down stress.

Fertilizer mis-application or spill
Misapplying fertilizer, filling the spreader on the lawn, and fertilizer spills can all cause brown areas.  Fill spreaders on the driveway or other hard surfaces and clean up spills. Make sure the spreader is calibrated correctly and is being used properly by making header strips and shutting of the spreader on turns. 

Herbicide Injury
Follow label directions whenever applying herbicides to or near a lawn.   Non-selective herbicides such as Round-Up or Finale can be misused and/or accidentally sprayed on lawns, causing brown areas.  Applicators sometimes make the mistake of stepping in the treated area, then onto the lawn, leaving behind a trail of footprints that later turn brown.

Poor and/or Compacted Soil
If soil is so poor that roots can't penetrate and fail to establish, brown areas may appear while the neighbors' lawns look fine.  Soil in areas frequently trafficked, such as footprints or animal paths, can become compacted and lead to a decline in lawn quality.

Lack of rainfall or irrigation can cause Kentucky bluegrass and perennial ryegrass lawns to go into a dormant state.  South facing lawns and slopes may begin to turn brown before other parts of the lawn from exposure.  These lawns can survive drought periods for a few weeks with intermittent rainfall.  Note: drought-stressed lawns are more susceptible to mechanical and heat damage.  To properly water a lawn, apply the equivalent of 1" of rainfall per week and water in the early morning so the turf has a chance to dry off by night fall.  Avoid frequent shallow waterings.

Buried Construction Debris
Buried block, siding, plywood, etc. can all cause dry areas where grass roots can't absorb sufficient moisture.  Unfortunately, in newer construction, buried debris is common.  If you can't determine a cause for browning, do some digging to investigate what is below the brown area.

Competition with Trees and Shrubs
Woody plants compete with lawns for water, nutrients, and light.  Plants with shallow roots may out-compete the lawn in hot, dry seasons.  Deep, supplemental irrigation in some areas may be needed to avoid lawn browning.

Dog Injury
Dog urine can be high in salt content and cause injury to lawns, especially if the soil is dry and infertile.  A dark green ring of grass can surround the spot, related to nitrogen contained in the urine.  Heavy watering reduces the salts to a less toxic concentration.  An application of Gypsum to the area will help to neutralize the urine salts.

Insects and Disease
The common lawn insects and disease can cause various patterns of dicoloration and browning.  Become aware of the signs to look for and the time of year that they are active in order to diagnose them accurately.  Correct diagnosis is essential for treatment which may include the use of fungicides and/or insecticides as well as cultural methods of control.