Keep your face to the sunshine and you cannot see the shadows. It’s what the sunflowers do. – Helen Keller

Sunflowers are believed to represent varied things to various cultures and faiths - loyalty, warmth, admiration, longevity, lasting happiness, bounty, appreciation, gratitude, harvest, friendship, and vitality.  

I've read that Victorian England took assigning meaning to specific flowers to a whole new level due to the social restrictions and stringent expectations of proper etiquette of that era.  Once could say a lot just by choosing a particular flower or opting to mix a distinct blend of blooms into a bouquet sent to a friend, lover, enemy or public figure.  Some folks to this day take to heart what giving a red rose means (love) as opposed to giving, say, a marigold (despair).

While I find flower dictionaries interesting, I can't say that floriography (the language of flowers) guides which flowers I buy, send or enjoy.  As for sunflowers, I have been a fan since my aunt grew them in pots along her driveway when I was a kid.  I even have a small collection of greeting cards with sunflowers on the cover.  Sunflowers, to me, are a lot like daises or a field of buttercups - cheerful and bright, perhaps a little showy.  They make me smile, and I'm always drawn to them.