My lawn is showing a lot of weeds in some areas (picture 1). The two previous years it only had mainly dandelion and some clover but this year new stuff has appeared. While pulling the weeds by hand I notice that many of them were growing right next to the remnant of the cores left during last fall's core aeration (my soil is clayey and cores don't disappear completely - picture 2). I believe that during aeration, seeds that were dormant could have been taken to the surface and germinate, but I never read anything like that. Any ideas?