Valentines day is traditionally the busiest day of the year for florists so it is recommended you get in early with orders. Prices for valentines day flowers are typically more expensive than other flowers because of this, particularly for red roses.

About Valentines Day
Saint Valentine's Day or Valentine's Day falls on February 14. It is the traditional day on which lovers let each other know about their love by sending Valentine's cards, which are often anonymous. The holiday is named after two men named Valentine, both Christian martyrs. The day became associated with romantic love in the High Middle Ages, when the tradition of courtly love flourished.The day is now most closely associated with the mutual exchange of love notes in the form of "valentines". Modern Valentine symbols include the heart-shaped outline and the figure of the winged Cupid. Since the 19th century, the practice of hand writing notes has largely given way to the exchange of mass-produced greeting cards. The Greeting Card Association estimates that, world-wide, approximately one billion valentines are sent each year, making the day the second largest card-sending holiday of the year behind Christmas. The association also estimates that women purchase approximately 85 percent of all valentines.
Source: Wikipedia