Keeping Cut Flowers Fresh as long as possible !
The flower preservative packets supplied by florist shops can be added to the water to keep the flowers looking their best.  If those aren�t available, you can mix up your own recipe. Begin by preparing a solution of lukewarm water to the same amount of lemon lime soda and a teaspoon or two of bleach. Even after a flower's been cut, it still needs to be fed. The sugar in the lemon lime soda provides nutrients to the flower and the citric acid in the solution allows the nutrients to be taken up more efficiently. The bleach keeps the water clean.  Whether you use a preservative or nor, you should replace the vase water every 3 to 4 days.

Before you slip the flowers into the solution, recut the stems under water at a slight angle; this is particularly helpful for roses. Also strip away any leaves that fall below the water line.

Follow these steps for any flowers you may receive as Valentine�s gifts as well as those you prepare to give as presents.  And remember to keep the flowers out of direct sunlight and away from sources of heat.

With these techniques you can expect your cut flowers to last an extra four to five days. Keeping Cut Flowers Fresh P Allen Smith Garden Home
What's the best way to cut flowers?
Flowers keep best when cut with a sharp knife (un-serrated) and plunged immediately into water. Always make a cut on a slant, as it exposes more stem surface area. Also, remove leaves that will be under water in the arrangement, but do not remove thorns from roses as it tends to shorten their life.
If you don't like to use chemicals to prolong the life of your cut flowers, there are "natural" alternatives. Some methods work better than others. Here's one for you: does a penny and an aspirin tablet placed in the vase water really do any good? Some say the combination does keep flowers fresh longer. The theory is that the copper acts a fungicide and the aspirin makes the water more acidic. Here are more food + acid combinations:
  • Add one part lemon-lime soda (not diet) to 3 parts water. Then to each quart of this solution, add 1/4 teaspoon bleach. Thereafter, add 1/4 teaspoon bleach after each 4 days of use.
  • To 1 quart water add 2 tablespoons fresh lemon juice, 1 tablespoon sugar, and 1/2 teaspoon bleach.
  • Add 2 ounces Listerine mouthwash per gallon of water. Listerine contains sucrose (food) and a bactericide. Listerine is acidic and is said help water move up the cut stem.

 
  • Use plain, lukewarm water for most cut flowers, but use cold water for bulb flowers, such as daffodils, hyacinths, and tulips.
  • Change the water every 2 days -- don't just top it off. This is the single most effective thing you can do to keep your flowers looking fresh.
  • Keep flowers out of direct sunlight, and move them to a cool place at night.
  • Give daffodils their own vase -- daffodil stems give off a compound that is toxic to other flowers.
  • Keep cut flowers away from fruit, which releases a gas that causes flowers to age faster.

 

What do do with faded blooms

First of all, don't throw them away. At the very least, cut them up and add them to the compost pile. Semi-fresh or partially faded flowers, depending on how you look at them, also have a second life in crafts and as edible flowers. Just remember, if you're planning to use them in food, make sure they are truly edible and free of chemicals. You can learn more about edible flowers in my How to Landscape with Edible Plants article.
  • Dry flowers and petals for use in sachets, wreaths, and aromatherapy projects.
  • Bake edible flowers such as roses and calendula in cakes, breads and cookies. For a 9 x 13-inch cake, fold 2 cups loosely packed petals into the batter.
  • Press flowers for making personalized note cards.
  • Add flowers to herbal vinegars.
  • Preserve edible flowers (viola, pansies) in sugar and use them to decorate cakes.
  • Use edible flowers as garnishes in salads, casseroles, and soups.

Thank you Marion: http://www.plantea.com/cutflowers.htm