Actually now I am thinking Chasmanthium latifolium , northern sea oats. I merely dabble in grasses, so I would wait for a better ID from someone more knowledgeable than I. The Siberian frost grass does has blooms as you can see in the link.
Definitely Sea Oats ... dead head those things before the end of the season, though. They reseed rather aggressively and are not terribly easy to get rid of once established (in other words, pluck up any volunteer seedlings the first weeks of spring). Otherwise it's a wonderfully handsome little grass that seems to withstand a great deal of abuse and neglect (not a pretty thing for a koi fancier to admit)