The significance assigned to specific flowers in Western culture varied
— nearly every flower had multiple associations, listed in the hundreds
of floral dictionaries — but a consensus of meaning for common blooms
has emerged.
Often, definitions derive from the appearance or behavior of the plant
itself. For example, the mimosa, or
sensitive plant, represents chastity. This is because the leaves of the
mimosa close at night, or when touched. Likewise, the
deep red rose and its thorns have been
used to symbolize the intensity of romantic love.
Pink roses imply a lesser affection,
white roses suggest virtue and chastity,
and yellow roses stand for friendship
or devotion. The black rose (actually a
very dark shade of red, purple, or maroon) has a long association with
death and dark magic.
"A woman also had to be pretty precise about where she wore flowers. Say, for instance, a suitor had sent her a tussie-mussie (a.k.a. nosegay). If she pinned it to the 'cleavage of bosom', that would be bad news for him, since that signified friendship. Ah, but if she pinned it over her heart, 'That was an unambiguous declaration of love ❤️'."
Later authors have been inspired by this tradition to create lists that associate a birthday flower with each day of the year.