The good news is the pictures I asked for and you gave me is not Poa. The bad news is the very first two pictures you provided is Poa. Dchall was saying it was ryegrass. I was correcting him in that it is Poa, and then I asked for closer ones of the the last two pics so I could see them better to be able to determine what they are. So sorry if I confused you. How've you been, by the way? I know how hard you worked on the lawn and really regret the Poa problem. I know it isn't your fault if that is any consolation at all. Wondering if you purchased, literally asked for sod quality seeds? And did they say "sod quality" on the bag(s) when they arrived? It is very disheartening for so many people to have a Poa problem after seeding when they asked for sod quality. But then, I have to remember and need you to know that Poa seeds are very often in the soil. Irrigating to get grass seeds to germinate will also prompt the Poa seeds. That's one explanation anyway since Poa seeds can remain in the soil for decades. After you know you've done everything right, Poa is very sneaky. On top of that, it cannot be pinpointed to a time of year because it exhibits both annual and perennial as well as multi-seasonal characteristics. Confusing I know, but it's a pretty smart weed. What it means is you can apply pre-m at the appropriate time and still end up with Poa the following year. The reason is that while the pre-m might prevent the new seeds from germinating and you won't get a new crop of Poa (the annual aspect), you surely will be revisited by the old crop the following year (the perennial aspect). And the awful cycle repeats itself. Additionally, your spring application of pre-m (the corn gluten) won't do much good because it's not germinating in spring, not much anyway. It makes itself known in spring, but that is from the fall germination period. Then, it waits through winter to become a menace in spring. All those little seedheads you see in the first two pics are the ones that will germinate in the fall. So you want to apply your pre-m in the fall to help prevent Poa annua and keep applying every fall for a few years. I honestly have no idea if corn gluten is effective at preventing Poa seeds from germinating. Hopefully, someone who has done it will chime in with their experience. While I do imagine it does work, I only know about the chemicals for certain. Also want to point out that pre-m, whether corn gluten or chemical herbicide, cannot prevent all weeds. It only affects those that grow from seeds. I'm afraid it has no affect on weeds that grow from stems and stolons. And if you're not yet miserable enough, there are those that grow by both seeds as well as stems and stolons. See if you can find the weed here. I want to guess purslane or chickweed, but the purple flowers are throwing me off.

What your neighbor has is Poa Annua or Annual Bluegrass. It is an annual that germinates in the fall and dies around May, that is why it has gone to seed. There are no selective controls for this as it is a type of grass. You can put out pre-emergent in Sept to stop the germination but be careful if you are also planning to aerate and seed as the pre-emergent will stop all grass seed from germinating.

Rodney, can you tell us where this is growing geographically? Looks possibly like something in the Apiaceae for starters. Can you show it again when those flower buds open?

Yep