Flowers have long symbolized love.
Nature Bulletin reports that only three flowers are mentioned in the Bible: camphire, lily and rose.
Solomon 1:14 in the King James Version says, "My beloved is unto me as a cluster of camphire in the vineyards of Engedi." Most modern Bible translations refer to camphire as henna blossoms.
Solomon 2:1-2 KJV says, "I am the rose of Sharon, and the lily of the valleys. As the lily among thorns, so is my love among the daughters."
The following infographic from Frugal Dad describes what various flowers symbolize. It shows that lilies are recommended for funerals and symbolize the restoration of peace. For Christians, the lily of the valley could have a deeper meaning: it could symbolize Jesus Christ.