Start with a very clean vase. Fill it with fresh, cool water; add one pack of the included cut-flower food to the vase. Handle calla lilies with care because they can bruise easily. Hold each stem next to your vase to gauge how much you'll need to trim. Using a sharp knife, cut stems at a 45-degree angle so they won't sit flat in the vase. This allows for better water absorption.
Calla lilies are particularly thirsty flowers. Use the extra pack of cut-flower food with your first water change. Check the water level in your vase often, and add more water as necessary. Recondition your callas every two or three days: Recut the stems, change the water, and add nourishment. To nourish the flowers after the flower food is used up, refill your vase with a solution of one teaspoon sugar and two drops liquid bleach per gallon of fresh water. Keep flowers in a cool area away from drafts and out of direct sun.