We grew pompas grass one year,it was a devil to get rid if, very invasive,you really will not need to save the seed,as it will spread by rizones,way faster than you will want, (maybe ) :0)
It is nice if you have a HUGE spot you want to fill in, but look out after that.
This is just our experance with it, i am sure others will have more to say on the subject.
Good luck to you.
Carol