If they're fresh and in bloom, it's a sign for health and success - particularly in a loving relationship.
If they're withered, it's a sign for disappointment.
Trampling on flowers may indicate you're trampling on someone's feelings.
Different colors and different species also have different meanings, e.g. a rose is a perfect symbol for the uniqueness of a person: beauty, thorns, and lifespan. Red usually signifies physical aspects, joy, and love. Light red stands for emotional warmth and authenticity, dark red speaks more to someone's desires and drives.