Could very well be poa trivialis. It likes shade and damp areas. In the summer, without water or with too much heat, it'll go dormant or die. It is a spreading perennial. Certainty is a selective control BUT NOT for TTTF, unfortunately. There may be others out there though. I know some studies have shown ethofumesate to be more effective at controlling poa triv than poa annua but others have shown no control whatsoever. There is probably no good chemical control for you. In the spring, does this grass develop thick stalks?

Haha, I was just about to say, I'd love to take any throw-aways off of your hands, ncangie! It looks like it may prefer to have a little more shade than it's getting, these usually grow on moist slopes and as an understory planting where they get bright early season light before the trees leaf out after which they provide protection from more intense summer heat/sun.

In the lawn, a tough competitor. But not even on the same page for overall destructiveness as garlic mustard or buckthorn-two plants that can prevent tree seedlings from developing on the forest floor. This one can't do anything like that, not even close. Which brings me to the subject of how everyone seems to have their own version of "invasive species". For some, they think that is just any plant-native or not-with aggressive ability to colonize a site. For others, it's a plant that can naturalize in the landscape, whether it is causing any problems or not. In reality, true invasive exotic species are those which can and do replace whole native plant communities, things like common buckthorn and garlic mustard...things where, once they get going, the total nature of the site is completely altered and simplified...usually down to just that one species. I've had Glechoma in my lawn forever. A few times, I've went through the trouble of controlling it, and this can be done as I covered above. Right now, it's back in full force, having crept in from the sides, but since I now suddenly have three grandchildren that do or will be playing on our grass, I've withheld the phenoxy stuff. I'll live with the ground ivy for now, and in fact, there is one thing I've always actually liked about it-the minty fresh smell whenever I cut the lawn. But to lump this one in with the bad invasives is just misguided. +oM

Glechoma hederacea - Creeping Charlie. It is easily removed in open ground. As you know it is more difficult to remove from grass and agree with fata that it is relatively benign.