Karen Myers, owner of Apples to Zinnias, has the secrets.
With very little effort, you can have beautiful flowers to enjoy for days and days. Keeping the water in the vase clean is the number one way to keep your flowers healthy and long lasting.
There are many recommendations that have been passed around. A few are adding a copper penny,putting in a small dose of bleach, or adding an aspirin. Those things can change the pH balance a small amount to keep the water fresh.
To clear the vase of all bacteria, hold the vase over the sink, holding the flowers in place, and pour out all the water. Immediately, replace with water that is a medium temperature. Flowers are sucking air and closing off their future ability to drink when they are out of water, so it needs to be done quickly. Doing this once a day is optimal, but even every other day will make a big difference in the life of the flowers.
Giving the stems a fresh cut will enhance their life even more. The larger the stem of the flower the more important it is to give it a fresh cut every few days.