I'm having trouble accessing your photo. I briefly saw what looked like Chrysanthemum paludosum but now can't see anything except ads. Can you put your picture directly in to your post? Just upload it straight from your computer using the camera icon below the message box.

photo here

oh yeah it really looks like that Chrysanthemum plant. It looks like seeds probably spread over the last fall because there were multiple baby plants all around the place. I wonder if I just leave it to be to spread on it's own, if it'll outcompete weeds and be an effective groundcover on it's own during the summer.

Thanks. Yes, C paludosum. I've never grown it so I can't comment further. But if it's happy in your garden I'd let it do its thing. But you'll still need to weed.