My neighbor has that stuff growing on his side of my driveway. I thought it was a weird nutgrass but after looking at the pictures on Wikipedia, it is definitely kyllinga. That area has been dug up several times since we lived there, so who knows where that soil came from. I used to maintain that as St Augustine and the weeds were not evident. I might have to try that again. I don't have problems with nutgrass like others in the area. I believe my success is due to infrequent watering. Nutgrass, also a sedge, likes to live in wetlands. You might not have as much control over the moisture in Houston, but I can go for weeks without watering because I water so deeply.

The other stuff looks serious as a weed that will choke out St Aug as fast as it can spread. Have you tried spraying it with strong vinegar on a hot, sunny day? I would start with that. Call around to garden stores and ask about 20% vinegar. The danger of using such strong vinegar is inhaling it or splashing it into your eyes. Inhaling it is not that much of a problem because it smells so very strong. Splashing it in your eyes will cause blindness for at least a few months. If that fails to kill the weed, get ready to lie around in the grass pulling it out. You'll probably have to get the roots. If you use vinegar, any overspray will kill the St Aug, too, but if you kill all the weed, you can let the grass grow in at your leisure.

Standing water is definitely an issue here. We are living in an area that was used for rice paddies not all that long ago - the gumbo is about as bad as that stuff can get. Then we had the builder's lousy dirt thrown on top of it (too lifeless to call it soil).

The sedges love this area, but hopefully, at least once we start eliminating the soil compaction they can't hold on as tightly when we try to get them out.

However, for the buttonweed, I've already told DH to brace himself for digging cuz I don't see any way around it. I desperately want to hear that I am wrong, but it spreads by underground pieces that break off very easily, as well as by seed & by the plant segments - it's as if it was made expressly to do nothing but multiply. I believe it must have escaped from hell rather than Virginia!

If you dig it up as soon as it shows up, it's not so bad, but once it establishes its roots underground - you have a serious battle on your hands. As we do since it took us over a year to get around to ID'ing it. :-P

Anyway, thanks for the feedback - I have some other unwanted volunteers in our landscaping beds that the vinegar would probably work on so I will have to find some of that stuff!