The clay under a south-suburban lawn packs down hard by the end of a summer of mowers, kids and August drought. Mike's Lawn Aeration Service opens it back up across Bremen Township — core aeration, overseeding and the lawn work that follows, timed for the cool damp weeks of September. A yard covered in soil plugs looks a little rough for a week, and then it comes in thicker than it has in years. Water and root find their way down where they simply could not go before. It is patient work with a delayed reward, which is the most satisfying kind to stand behind.