It is easy for fresh-cut flowers to die more quickly when you do not have the packet of plant food that comes with them. This is because tap water is not acidic enough by itself to prevent the growth of bacteria since its pH is too high. In addition, fresh-cut flowers need nourishment in the form of sugar. Fortunately, plant foods are not difficult to make at home. Always remember to trim an inch or two from the bottoms of flower stems as you place them into new water to ensure that the uptake tissues are healthy.
Citrus Soda and Water
Mix a half-and-half solution of citrus soda and water in the vase you plan to put your flowers in. Be sure to choose regular citrus sodas, not the diet forms, such as regular 7-Up or Sprite, for example. The citrus juice in them will provide enough acid to help prevent bacterial growth and the sugar in them will nourish your fresh-cut flowers. You will need to change the mixture in your vase every other day because there is not enough acid in the citrus soda to keep bacterial growth away indefinitely.
Lemon Juice, Sugar and Bleach
Pour two tablespoons of fresh lemon juice, a tablespoon of sugar and a half-teaspoon of household chlorine bleach into a quart of water. The lemon juice will lower the pH, the sugar will give your cut flowers nourishment, and the bleach will help to prevent bacteria from growing. As with the first homemade flower food, you'll want to change the water, only in this case every three days instead of every other day, because bleach is better at keeping the growth of bacteria down than citric acid by itself.
Sugar and Vinegar
Mix two tablespoons of white vinegar and two tablespoons of sugar into a quart of water. White vinegar is acidic and will curb the bacteria that may grow because of the sugar. Sugar encourages bacteria growth while at the same time it feeds your flowers. Without something acidic in the solution, your flowers would quickly die because the bacteria would infect the water and your flowers as well.