It is hard to fight poa with an organic program. Overseeding is one technique by providing competition, however if your seed germinates slower than the poa annua seed that is waiting to germinate in the fall, ie. kbg, you are fighting a losing battle--poa seedlings will be up and running before your seed even starts to germinate! If you have dense patches of poa, I would recommend you round those up (yes, chemical) now...less seeds to spring up later. And I don't care what anyone says about CGM, it is completely inferior to chemical preemergents by a wide margin. If you have diffuse poa throughout but not dense, it may not be as much of a problem and a healthy dense turf may outcompete it. I wish you good luck in any case.

I don't know of any reports confirming CGM prevents PA germination, especially since a lot of people don't really seem to understand PA is entirely opposite from usual pre-m practices. Being that I only recently returned to the forums regarding lawn care following a two-year absence, I don't know if anyone has reported success with fall applications of CGM. You have to know controlling PA and overseeding is not possible using organic methods. If you want to consider putting off seeding until the fall of 2008, you can expect some success, but, that's only if CGM is effective. As I said, I really don't know.