The Ghost Downstairs
Lots of mentions; the Seattle mansion has a lovely garden, and tending it is among Ren's duties. This may be my favorite flower moment:
"She walked to a clump of daffodils growing at the base of a tree, picked one, and brought it back to the grave. She kissed its petals before dropping it."
Hey, it's summer. Lots of stuff's in bloom:
"But he did say we'd go out into Woodbine Park and eat in the rose garden. That sounds kind of romantic, doesn't it?"
"It sounds suspiciously romantic."
What Scotland Taught Me
Eva is interested in botany and horticulture, and notices violets sprouting in Edinburgh at one point. She also notes regarding one of her crushes:
"...he smelled like that alluring bed of carnations, with a dose of boy pheromones sprinkled on top."
Of Ghosts and Geeks
Paul is Gwen's gardener, so naturally flowers and other green growing things abound. Their first scene together is a skirmish over the little daisies in the lawn:
"They're in the grass. You wanted the grass cut, right?"
"Yes, but not the daisies. They make this gorgeous spangled carpet of--" She stopped before she started comparing her lawn flora to some scene from a fantasy movie. "Don't cut those!" she repeated.
This one probably has the fewest number of flower mentions, because my narrator is an 18-year-old urban male who doesn't think about stuff like that. Still, Daniel does think briefly of making out with his girl-crush "under lilac trees" come April. And when sidling up close to her, he notes:
"Her hair smelled delicious, like apples and the star-shaped white flowers that grew all round a French hotel I had once been to."
(Daniel has no idea that was jasmine, but it was, of course.)
In my novel in progress, a Hades/Persephone story, flowers and other plants play a huge role. After all, in the original myth, what was Persephone doing when Hades kidnapped her? Yep: picking flowers.