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.