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?
my guess is that the tool used to do the aeration was not clean and brought the seeds with them from a previous job.
Equally, many seeds can persist in the soil for decades, and germinate when suddenly exposed to light. There's been a case in Britain where a native plant (Fen Ragwort Senecio paludosus) that had become extinct over a hundred years ago, reappeared after someone dug a drainage ditch and brought up some ancient seeds.
I would expect that more than aeration is needed to improve the lawn. I'm not a lawn expert but topdressing and raking in sand and sifted compost would help with the quality of the soil and ultimately the health of the lawn - so it is healthy enough to outcompete weeds.
