Horseweed. It used to be called Conyza canadensis, but the nomenclature folks decided relatively recently that it is instead Erigeron canadensis. This does seem to be particularly bad this year. Don't let it go to seed since that will make it worse and in more places next year. It is easy to pull if you grab it low enough, so I would try to pull 50 or 100 a day and keep the rest mown as low as possible, though they may still seed around some.

Thinere may be some type of broadleafed weedkiller that would work on it, but I prefer not to use them. For next year, a pre-emergent herbicide would help decrease seedlings, but again I know little to nothing about them.

The best time to do grass seed is midSeptmber in our area since the soil is warm but the seed is less likely to dry out or be stressed by heat. So if you overseed grass in the fall, you can use the preemergent in the spring since it only works to prevent seeds sprouting. There is regular chemical Preen, but they also sell an organic form made from corn gluten.

The really good thing is that it is an annual. That means if you follow NHBabs advice to not let it go to seed you've done a major part of controlling it for next year. It does pull easily. The roots are shallow, but they can hold on fairly well. Good tug and they are up. They invade my shady areas every year, but I'm winning the war as there are less and less each year.

You've got quite a collection of them. I know it's so very frustrating. Keep us updated!

Good to know what this is & how to deal with it! I have this annoying weed too.

The invasion started a couple of years ago with just a few in a shady corner that never seems to grow much grass (despite annual autumn overseedings). But now I see more popping up all over my small lawn.

Time for some serious stooping & pulling!

THANK YOU!!!!! I have been trying to identify this thing for 3 years! I'm usually great at finding mystery plants but this one and one other had me stumped. They multiplied like crazy this year thanks to us deciding to not now our hillside last year. This year we are mowing.