Clean the vase or container with a solution of 9 parts water and 1 part household bleach. Rinse the vase thoroughly after sterilizing. This step is unnecessary if the vase has never been used before.
Make a smooth cut to the base of the narcissus stems, using sharp pruning shears or scissors.
Place the narcissus stems into a bucket filled with water; this allows the sap to drain out, but is only necessary if adding the flowers to a mixed arrangement. Allow the stems to remain in the water for approximately 12 hours.
Fill the vase with enough water to submerge the bottom 2 to 3 inches of the stems. Mix cut flower food into the water and add the narcissus flowers.
Place the vase in an area that maintains temperatures of 75 degrees or below.
Trim the bottom ½ to 1 inch of the narcissus stems every two to three days. Refill the vase with fresh water and additional cut flower food.