Keep the vase filled (or floral foam soaked) with water containing a flower food. Flower foods make flowers last longer but it is important to follow the mixing directions on the flower food packet. Flower foods should not be diluted with more water than is specified on the packet. If the flower food solution becomes cloudy, replace it entirely with properly mixed flower food solution. If possible, re-cut stems by removing one to two inches with a sharp knife. Be sure to use a sharp knife or clippers that will not crush the stems. Immediately place the stems into solution. Keep flowers in a cool spot (65 to 72 degrees Fahrenheit), away from direct sunlight, heating or cooling vents, directly under ceiling fans, or on top of televisions or radiators. Most flowers will last longer under cool conditions.