Is there a difference? I've a couple that came home from the swap last year, and others I've grown from seeds that came from the Winter Blues swap... and even one marked Nodding Priarie onion. Is there any difference?
Yes, one is Allium cernuum and one is Allium stellatum. You can Google images or descriptions on how to tell them apart. I bet it's a subtle difference. I think the nodding onion really is supposed to have more of a drooping rather than upright flower. Wouldn't be surprised if they cross-pollinate, creating mixes even harder to tell apart.
Nodding onion definately does - that's what I have :)
The two that I brought home from the swap last fall are the only ones blooming this season, and they are definitely upright, so they must be prairie onions, or at least a cross that includes some of that variety. The pictures I found online also showed the nodding onions as a kind of pinkish color and mine are pure white. Maybe that can vary as well, but the pink seemed pretty consistant for the nodding onions in all the photos I could find.