Each spring at the Iowa State University Plant Disease Clinic, a flush of calls, e-mails, and samples arrive from people concerned about large "dead" patches of grass. The description of the problem usually includes an observation that the patch gets larger every year. Upon closer inspection of the grass, one can see that there are no spots on the blades or darkening of the roots or crowns (the part of the plant at the soil line). However, one also might notice that the "dead" plants aren t Kentucky bluegrass or ryegrass as expected.
Certain grasses, such as zoysiagrass and nimblewill, can be invasive in Iowa lawns. Both are warm-season grasses that don t begin to green up until the middle of May. They perform well during the heat of summer when cool-season grasses, such as Kentucky bluegrass and ryegrass, struggle under stressful conditions. In early fall, when temperatures begin to drop and the health of cool season grasses begins to improve, warm season grasses start their way into dormancy.
This spring, besides the usual warm season grass patches, there were many lawns with large areas that were killed from winter drying. Because the winter was mild, grass plants continued to actively transport water to leaves and into the surrounding air. Besides being mild, the winter was also very dry, so grass plants weren t able to replace the lost water. These killed areas may need to be reseeded. With all the moisture this spring it s important to avoid overfertilizing. Many fungi that thrive in moist environments also love to feed on excess leaf growth. Also, keep lawns cut at approximately 3 inches can help in maintaining a healthy lawn. Remember to keep the mower blades sharp.
For more information on maintaining a healthy lawn, see the following Iowa State University Extension publications:
- Maintenance fertilization of turfgrass, PM 1057
- Turfgrass management calendar: Kentucky bluegrass lawns, PM 1063
- Mowing your lawn, PM 1213
- Thatch control in the home lawn, PM 1756
- Establishing a lawn from seed, PM 1072
- Sodding a new lawn, PM 491
This article originally appeared in the 5/16/2003 issue.
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