This is Dollarweed, aka Dollar Grass. I keep looking for some reason to like it, for some neat bug that uses it - something to alleviate the aggravation I feel when I can't eradicate it! Nope, so far it's just a vile weed.

I have noticed that it likes to be wet. Sprinkle a little less, and it goes away.

Then it rains...

Usually Dollarweed in my lawn is small, probably because it gets mowed before it can grow this large. I found this one growing elsewhere, and had to take a photo because I'd never seen one so big. Wow!

There is another plant that grows down here in Florida that you might confuse with Dollarweed. It's Dichondra repens. There's also a very similar wetland plant.

I found this forum where Dollarweed (called Dollargrass there, and Pennywort elsewhere), is bothering other folks too. Julie suggested to Ragley that applying an herbicide with a brush on just the Dollarweed might be another way to combat it. I'll give that a try.

Since we're on the subject of which one we have, I've discovered that there are several kinds of Dollarweed. Does anyone know how to tell the difference between bonariensis, umbellata, and verticillata? According to the Atlas of Florida Vascular Plants, mine could be any of the three. When I get around to it, I'll look it up more carefully; in the meantime, if you know how to tell them apart, please tell me.

Here are the small white Dollarweed flowers:

That dot in the top left corner is a fuzzy fly (it was moving), which so far is the only type of bug I've seen enjoy the Dollarweed.