Romance cannot be expressed without flowers. And if flowers are the language of love, do you know the meaning of flowers? Communicating with flowers between people started since Biblical times. During the Middle Ages flowers were believed to be a source of magic. But they took on a whole new set of meaning in Victorian times.
People in love cannot express themselves so each plant had their own meaning, and even scents of flowers on a handkerchief can be interpreted as a message. Flowers didn't always convey love and romance though. Flowers also have a negative message. So make sure you're sending a positive message to your lady love or your beau or else they might take it the wrong way!
Romance ecards have prepared a quick "romance of the flowers" cheat sheet

Rose

When it comes to love, passion and romance, a rose can say a lot of things. The word originates from the Latin word rosa meaning 'red'. Rose is a symbol of love even with the Ancient Romans. It's also the official flower for the 15th wedding anniversary and is the flower for June. Different colored roses mean different things.
Here's a list of meanings depending on the color of the rose:

Burgundy: Beauty within.
Coral: Desire.
Dark Crimson: Mourning.
Hibiscus: Delicate beauty.
Lavender: Love at first sight, enchantment.
Moss: Confessions of love.
Orange: Fascination, display feeling of enthusiasm.
Peach: Desire, gratitude, appreciation, admiration, sympathy, modesty.
Pink: Happiness, appreciation, admiration, friendship, sympathy.
Dark Pink: Thankfulness.
Light Pink: Grace, gladness, joy, perfect happiness, please believe me, gratitude, admiration, gentility.
Red: Love, passion, respect, courage, I love you, beauty, pure and lovely, prosperity.
Deep Red: Beauty without self-conscious.
White: Innocence, purity, secrecy, I am worthy of you, silence, friendship, truth, virtue, girlhood, humility spiritual love, but of the soul, reverence, charm, happy love.
Yellow: Joy, friendship, true love, decrease of love, jealousy, try to care, freedom, slighted love, shows "I care", joy, gladness.
There are other meanings to roses too depending on how you present them. Here's a list that might become handy in the future --
Rose leaf: You may hope.
A single but full  bloom rose: I love you, I still love you, new love.
A small rose bud: Pure and lovely, beauty and youth, a heart innocent of love.
Thorn less rose: Love at first sight.
White, Dried rose: Death is preferable to loss of virtue.
Bouquet of mature roses: Gratitude.
Red and white roses together: Unity, flower emblem of England.
Yellow and red roses together: Happiness, congratulations.

Yellow and orange roses together: Passionate thoughts.

Carnation

Roses are not the only flower of love and romance. Carnations too can be interpreted with meaning. Although not as extensive as the rose, carnation can mean "yes", "fascination", "distinction", "divine love". Carnations are the flower of January.
Here's a list of floral meanings depending on the color of the carnation:

Pink: A woman's love, "I'll never forget you", mother's love.
Purple: Capriciousness.
Red: Admiration, my heart aches for you, fascination, "Alas! For my poor heart."
Striped: Refusal -- "No, sorry I can't be with you."
White: Ardent love, pure love, innocence, faithfulness, sweet and lovely,  good luck.
Yellow: Disdain, rejection, you have disappointed me.

Iris

Iris, the fleur-de-lis -- literally means "flowers of the lily" --  are the emblem of France. It represents wisdom, faith, hope, valor. It can also mean "your friendship means so much to me", and "my compliments."
Here's what different colored Iris mean depending on the color:

Blue: Faith, hope.
Purple: Wisdom, compliments.
Yellow: Passion.
White: Purity.

Tulip

If you want to compliment your lover you can send them tulips. They mean "perfect lover." They're also the emblem of Holland.
Here's a list of what different colored tulips mean:

Red: Declaration of love, "believe me", fame.
Variegated: Beautiful eyes.
Yellow: Hopeless love, "there's sunshine in your smile"

Violet

Violet flowers were worn by the ancient Greeks to clam tempers and induce sleep. It's also the flower for the 50th wedding anniversary. It's the flower of Feburary. Violets mean faithfulness, modesty, innocence, and understated beauty.
Here's what different violets mean depending on their color:

Blue: Watchfulness, faithfulness, I'll always be true.
Purple: Thoughts of you, blue love.
White: Let's take a chance, youthful innocence.
Yellow: Love of country.