Thanks for your question. I need three further pieces of information:

1).  How do you know it is a perennial?

2).   How is it coming from your neighbor’s yard?  Is it spreading on the ground from his/her yard?  Are seeds from your neighbor’s yard being blown into you yard?  

3). Is this the first time you’ve noticed it, or have you seen it in past years as well?

Many thanks. Looking forward to your response. 

Thanks for your response. I have a pretty good idea what it is. It’s a type of grass.  Grass does not spread by spores. I suspect  that you might have sodded your yard recently. If so, when. If not sodded have you recently overseeded your turf. If true, what was the composition of the seed you used. Your situation is purely cosmetic but I do understand that you want to improve its appearance. 

One final question. Just because your neighbor’s yard has this “weed” in it, can you be sure that it has spread to you? Might it be possible that it independently arose in your yard?  What about your other neighbors?  Do you think that your neighbor’s “weed” spread to them as well?  Give some thought to my question as your answer will be central to my suggestions to you.

Improving the appearance of your turf  will be my goal .

Thanks for consulting with us.