Water should be changed approximately every 3 days, or sooner if you notice the water becoming cloudy. This rule will help you avoid the accumulation of bacteria in the water, which causes mold and accelerates the death of flowers. With each water change, the flower stems should be recut. Why? Because when you change the water, an air block forms in the stems of the flowers at the cut side. To continue water adsorption a fresh cut is needed.