The novel ends with a weird mix of climactic showdown and hint of romance, with Bayard returning home after facing down Benjamin Redmond, finding that Dru is gone, and smelling the verbena flower she left on his pillow. So it's a flowery ending (excuse the pun), with the scent "filling the room, the dusk, the evening with that odor which she said you could smell alone with the smell of horses" (7.4.36).
We could take it as a metaphor for the whole book; Dru's scent remains even after she's skipped town, just like the Southern spirit remains even after it should have been squashed by defeat in war. Pretty powerful, ain't it?