Roses are a better symbol of lasting love when you change their water long enough to keep them healthy. How often to do that is a source of some conflict -- advice ranges from daily to every four days. Err on the side of frequency to keep those carefully manicured stems in clear, clean water; a daily water change is ideal. But don't neglect the other things you can do to keep cut rose blooms from wilting.
Leafless With Flower Food
Get your cut roses into a sterilized vase ASAP, in warm -- not hot or cold -- water doctored with floral preservative. Fill the vase halfway, and dissolve a packet of the flower food in the water. You can make your own flower food with a mix of 2 tablespoons of white vinegar, 1 tablespoon of sugar and 1/4 teaspoon of bleach in a gallon of water, or 1 part non-diet lemon-lime soft drink to 3 parts water, plus 1/4 teaspoon of bleach. Prepare the roses by removing the leaves that will sit below the water line and cutting 1/2 to 3/4 inch from the base of the stem at a 45-degree angle. The angle is important because the roses will rest on the points, leaving the rest of the stem's base open to the water. Use a clean, very sharp blade to cut the stems so you don't crush them; crushed stems prevent the flowers from absorbing water. Ideally, you want to cut flower stems when they're submerged -- in the vase or in a stoppered sink -- so they begin to "drink" immediately. Each time you replace the water, replace the flower food as well. The sugar in the food promotes long-lasting blooms and the bleach inhibits bacteria.
Recut the stems each time you change the water to keep their water-absorbing channels open. Display your roses in a cool, shaded area once they have bloomed. Flowers last longer out of direct sunlight or proximity to hot lamps or appliances. Keep the roses away from bowls of fruit and other plants. Fruit, in particular, off-gases ethylene, which wilts flowers. Don't use softened water for the vase. It contains salts that will kill the roses. In summer, or in very warm conditions, top off the vase water with an ice cube or two to cool the water down. If you can store the vase of roses in the fridge overnight, the blooms will stay fresh longer.