Wow, thanks for the answer! That was fast!

Yes, Arundo donax, and it grows everywhere around Austin. Makes great cane poles for fishing. It will grow to over 20 feet and is very cold hardy. It is drought tolerant and can grow in very wet conditions. I have a variegated form growing in my yard. The Highway Department and County workers, plant it along roadsides to prevent erosion. It spreads relatively slow, only a few inches to a foot each year depending on type of soil, moisture, and fertility. Kt

This is a North American native plant. In the right place, like at the back of a border, it is absolutely stunning. It is a good wildlife plant -- birds were how this it was probably planted to begin with. From the Lady Bird Johnson organization there in Texas: http://www.wildflower.org/plants/result.php?id_plant=PHAM4 http://www.wildflower.org/expert/show.php?id=9424 FataMorgana

Yes, I recognize this is an old post, but for the benefit of others landing on this page... I'm 99% sure this is Creeping Beggarweed or Spanish Clover (D. incanum/D. laxiflorum). Mine produce a deep pink, almost purple flower. I spent an exhaustive afternoon in my back yard digging a ~6' x 6' patch of it out of my St. Augustine about 2 yrs. ago. I would compare the underground root system to that of Torpedo grass... invasive and virtually impossible to eradicate. My temporary joy of digging out the mother lode tap root (at least 10" deep!) was quashed when sprigs of it started popping up again. As the natural/organic method failed, I got some Roundup. The grass has almost fully recovered now; I get an occasional sprig though. Then I noticed it was invading a stretch of front yard near the street. Mother Nature sent Irma to help me with that area. Put the debris pile on top of it and by the time it was picked up, mostly everything was dead underneath. It made it easy to pull most of the roots out then. So for the sprigs that have survived both there and in back, I take a can with both ends cut off, slip the weed inside of it (Beggarweed and/or Torpedo), and try to protect the surrounding St. Augustine as I spray the Roundup. My condolences to anyone battling this... good luck!