Starting in the late morning, every single flower, berry, fruit, acorn, nut, pinecone, etc in the entire resort will be turned into a green rose. Every single one of them. On the trees, in the bushes, in the grass. Long stemmed, short stemmed, thorns, no thorns. Doesn't matter. They're all green roses.
This is Anna's way of getting back at Petersen. Probably only Petersen, Gabe & Zira will know Anna did it. Although Cas, Dean & Jo might suspect because they've seen the roses Petersen gave her. (which she has trashed, btw) edit: and Robin... he will know as well, but just cuz he's Robin and knows her better than she knows herself most of the time :P