A.k.a. Capeweed or match-head - it's a larval plant for some butterflies, I believe.

Torenia.

WOW!! That is it! I have searched all summer to find out what that plant is. I love flowers but I am not plant savvy with all plants. That is it!! Thank you!!!!!!!!!!! But what I am reading is that this is native to Missouri and grows in waste land. I live in OHIO and in a nice neighborhood and no waste land around not even a new home being built. Where did this come from? And where it was growing I have put flowers in every year for the past 11 years and have never seen this before. I can't tell you enough times thanks. It is really a beautiful flower and I had planned on tossing some of the seeds in the back of our property at work. There is a very large wooded area and I have been tossing some of my flower seeds this year to see if any of them will grow next year. So far 1 single pink malva has sprouted up and over and around a large patch of jewel weed and bloomed a few buds to end this season. I have tossed Cosmos, Zinnias, and pink Malva, plus some Echinacea. We feed the birds and the squirrels. There are butterflies and hummingbirds too. And I thought that this yellow flower might like to grow along some of the trees since it seemed to tolerate shaded areas. Thanks again for your help.

Looks like a catmint to me :0) I've not had mine spread rambunctiously but the plant itself does tend to sprawl outward - easily remedied by whacking back with the added bonus of whacking being another round of bloom. Of course it increases in size each year, but again very easily remedied by dividing - after which it doesn't miss a beat so go ahead and whack and divide all you want, this plant couldn't care less. I get a whiff of something when I disturb the foliage - not minty to my nose, though. Whatever it is, I don't particularly care for it but it's not off-putting per se.