Flowers: If you receive roses for Valentine’s Day, re-cut the stems under cool water an inch or more from the original ends (preferably before the heads start to droop for best results). A fresh cut helps eliminate air bubbles in the vascular tissue (the tissue that allows for water uptake) that can block water from being absorbed, which causes the wilting. Air bubbles enter the system when the flower is first cut from the stem (if not cut underwater — and keep in mind the flowers are often shipped great distances). It can also occur during the transfer to the vase. Some people have success with submerging the whole bouquet and letting it soak for about 20 minutes after re-cutting the stems underwater. Or, you may be fine with just re-cutting the ends.
Do use floral preservatives if any came with the flowers. You can use a home-made floral preservative if the bouquet didn’t come with one. To make it, use two tablespoons of lemon juice, one tablespoon of sugar, and a quarter-teaspoon of bleach per quart of water. Add another quarter-teaspoon of bleach to the vase every 4 days (or just a drop or two if it is a small vase). Change the water after 3-4 days to maximize the vase-life of the flowers. It is best to use distilled water. Definitely, don’t use softened water, as the salts will decrease the life of your flowers.
Finally, display your flowers in a cool area away from direct sunlight and away from drying heat sources like woodstoves or heat registers.