The keys to extending the vase life of any cut flower are to provide ample fresh, cool water and to ensure that the flower stem can easily take up the water provided. Controlling the buildup of bacteria that forms in the vase water will help to keep water fresh and extend the life of cut blooms for as long as possible.
Re-cut your flower stems when you get them home by holding under running water or in a sink filled with water and cutting while submerged. This will ensure that an air pocket does not block the stem and prevent the uptake of water.
Remove all foliage that touches or falls below the water line on the vase. Leaves will rapidly decay in the water, fouling it and creating bacteria detrimental to the flowers.
Treat the water with a a packet of commercial floral preservative to feed the blooms and keep bacteria down. Alternatively, make your own preservative by mixing 1 teaspoon of white granulated sugar and two drops of household chlorine bleach into the vase water, swirling to dissolve.
Place the flowers in the treated water and locate the vase somewhere cool, out of direct sunlight and away from heating vents.
Change the vase water daily or every other day. Rinse the vase well at each refilling and add fresh preservative. Re-cut the stems removing just a 1/4 inch and remove any new foliage the falls below the water line as the stems are cut down.