Any way to use them besides for a quick profit.
The uncommon flowers (roses / tulips / lilies) have emotion bonuses. What I can tell you for sure is that four flowering tulips give +2 to energized, and when I harvest the flowers that drops to +1. Roses have a flirty bonus, and lilies have a focus bonus. I'm still furiously growing and experimenting to see how many plants it takes to get the bonus, or if quality makes a difference. I have 4 perfect roses in a box that only give a +1 flirty, so I'm currently growing a vast forest of them to see if it's possible to get +2, and how many plants it would take.
I'm going out on a limb, but I guess an orchid might have an inspiration bonus. Maybe there's a flower that gives a playful bonus?
MINI UPDATE:
A single flowering rose / tulip / lily plant will give +1. Quality doesn't seem to matter, but being in bloom does. If you harvest the flowers, the effect goes.
Four tulips will give +2 to energized,
Eight roses to get +2 to flirty,
Eight lilies to get +2 to focused.