Q: After I mow my bermudagrass, brown swirled areas are left in the yard. I use a self propelled push mower with mulching blades. Would the mulching blades cause this?
A: The swirls are normal at this time of year, particularly if you have any low spots in the lawn. Bermudagrass grows markedly slower after mid September. Whereas in summer swirls caused by low spots were quickly covered by new green leaves, now they are evident for several days, if not weeks.
Put your mower away for the winter. The swirls will disappear as the grass turns brown. Next year try to level your lawn and be cautious how often you mow after early September.