My guess is something in the Lamiaceae (Mint) family. Lots of possibilities...hard to identify (for me) even with a detailed verbal description.

I found it (online search)- Asiatic dayflower. Can be a pest (of course!).

Buy, was I off. It is on KY's invasive exotic plant list (http://www.se-eppc.org/ky/list.htm).

Great, invasive. Fits right in with the Japanese honeysuckle and knotweed and bindweed. Only thing I haven't found yet is garlic mustard, but no doubt it is there somewhere. And I'm the one who wouldn't let the builder bulldoze that area - I wanted my "woods"!!!

It too bad you have some weeds in you woods.Something you will have to contend with.But a lawn is 100% weeds with zero asthetic and ecological value,Better something than nothing.

nywoodsman - my comment was referring to invasive(s). Only because of the work for me in trying to keep, the Japanese honeysuckle in particular, under control so native plants and trees aren't choked out of sight and existence.