What Causes a Brown Patch on Grass?

• Brown patches of grass can be caused by a number of conditions. Nick M Do/Photodisc/Getty Images

  Brown patches on an otherwise green and healthy lawn can cause some concern. After investing time and money into your lawn, you don't want to see it all turn brown. Although there are several causes of brown patches, there are also measures that can be taken to prevent or reverse brown patches.

Root Rot

• A poorly drained area of the lawn can quickly turn brown. Poor drainage means that the water remains in one spot for 24 hours or more. The prolonged exposure to moisture causes the grass roots to rot, and as a result, the grass will die and cause a brown patch. Ensure that your lawn is well drained to prevent this from occurring. Avoid overwatering the grass or watering it when a good rainfall has just passed or is forecast for the near future.

Soil Compaction

• Densely compacted soil can contribute to brown patches of grass. Compacted soil is very hard, almost like stone or concrete, and is difficult for grass roots to penetrate. Sod layers and grass seeds need soft, pliable soil to root properly. If the soil is not soft enough, grass seeds will never root and sod layers will die within about a year. To ensure adequate rooting of grass and prevent brown patches on your lawn, plow the soil thoroughly before installing sod or sowing seeds. If the grass has already begun to die and form a brown patch, it may be necessary to replace the sod or reseed the area.

Fungus

• Some brown patches of grass are caused by a fungus that is always present. These brown patches are typically doughnut shaped, with an area of green grass in the middle of the brown patch. At times, a white fungal web may be seen at the edges of the brown patch. To help combat fungal-caused brown patches, it is important to keep grass healthy. Water your grass in the morning after the dew has dried or after dark, because the fungus requires 14 to 16 hours of wet leaf surface to reproduce. Avoid fertilizing the grass during June, July and August to decrease the severity of the brown patches. Maintain grass heights at 2 or 3 inches, as grass that is shorter or taller is more vulnerable to the fungus. As a last resort, opt for a fungicide to help control the brown patches. Although extremely effective, fungicides can be costly, particularly if you have a large lawn.