The rosehip is the answer. I'm sure we could extrapolate many meanings for its every use. In the end, it's simply and old children's song.

[A folk song sung to children, not a warning, not a threat. Perhaps a lesson in not mistaking something for what it is not, perhaps just a song. They are the kindest words he ever sang to her, in some way, unburdened by his expectations for her.

But that, too, is a kind of lie.

He runs his thumb over the back of one hand.]

I'm afraid that is all there is to tell.