This LOOKS like Solidago (don't know which one), but it's much taller (~6 ft) than I'm used to seeing, and the form of the plant looks more shrubby. Stems are woody. Any help much appreciated!
It looks like a Solidago. I suggest looking at the USDA site to see which species occur in your area. http://plants.usda.gov/ Enter the scientific name, and that will give you maps of each species. Click on the state and you will see what counties it has been reported in, which will give you a general location, since it probably occurs in other counties. Then use a guide such as the latest one, Shinners & Mahler's Illustrated Flora of North Central Texas, which if you don't have a copy is also on the Internet http://artemis.austincollege.edu/acad/bio/gdiggs/NCTXpdf.htm Even if you are in South Texas, a lot of the same species occur in both areas.
You might have trouble finding the maps to all of the species on the USDA site. After entering the scientific name and clicking on that, you must scroll down and find just the genus listed and click on that. This is what you should end up with for Solidago http://plants.usda.gov/java/profile?symbol=SOLID
The photo was taken in October (we're in Coastal Texas, just south of Houston, so it's pretty much like late summer). I looked at every Solidago I could find that had the linear (or nearly linear leaves) and height that's listed for Brazoria County, still can't find it. Maybe it's one which isn't listed as occurring here. I pretty much ruled out S. altissima based on the entire margins on my plant and the length of the corolla tubes--looks longer than S. altissima. But I'm such a novice, I could well be wrong.
It may not be a Solidago. There are a lot of composites and to identify some of them you just have to have one, a good scope to look for minute details, and use a key. Another guess would be a Senecio.
Hmm. I think I'll look for it in the same field (it's on my property, near the woods) this fall and dissect a flower, take closeups of the leaves etc., and try again. Thanks for your help, all.