To prolong the life of fresh-cut flowers, cut off an inch of the stem at the bottom, place in a clean vase filled with a mixture of water, sugary soda such as 7-Up or Sprite, and a few drops of bleach and place the vase in a bright, cool spot. Alternatively, mix diluted vodka into the water to help inhibit wilting.
Before placing fresh-cut flowers in a vase, trim half-an-inch to an inch of the stem off the bottom of the bouquet to prevent blockage in the plant's intake system and remove bacteria. In a clean vase, mix equal parts water and 7-Up or Sprite with a few drops of bleach to inhibit further bacterial growth. The soda provides the necessary sugar to keep the flowers fresh, with the added benefit of citric acid increasing the acidity of the water, so it travel up the stems faster than neutral or basic water.
Another option is to use vodka to help inhibit ethylene production, which helps stall the wilting process. To avoid harming the plant with a high concentration of alcohol, dilute the vodka before adding it to the water. A more effective preservative, silver thiosulfate, also inhibits ethylene and is more commonly used by growers.
To keep flowers looking fresh after these initial steps, keep the vase in a cool, bright spot and trim another inch from the bottom of the stems every three days.