We use flowers to say so many things, from "I love you" to "I'm sorry" and everything in between. Humans have been using flowers to express and punctuate feelings since the dawn of time and so over the eons certain flowers have come to symbolize certain things. The meanings of flowers can vary based on culture, context, and occasion but here are some popular blooms and their most commonly associated messages.
The Romans and Greeks both associated roses with goddesses of love (Aphrodite and Venus) and although roses today are most often used to express romance and passion they can have other meanings as well.
Red -- Love, Passion
Yellow -- Friendship, Jealousy
White -- Humility, Innocence, Purity
Pink -- Gratitude, Admiration, Happiness
Dark Crimson -- Mourning