Roses are a popular Valentine’s Day gift, but they often die so quickly there is not much time to enjoy them.Usually when people put roses in tap water, bacteria in the water are pulled up through the stem, blocking the little tubes in the stem, said Michael Knee, professor of horticulture and crop science.The bacteria grow and feed on the food reserves inside the stem, he said.”Four or five days is probably as far as (roses) will go if put in regular tap water,” he said.Placing a preservative in the water can double the life of the roses, he said.Preservative packets that come with store-bought roses contain sugar, a source of food, and a bactericide, which kills the bacteria in the stem, Knee said.Cutting about an inch off the bottom of the stem at an angle will also help to eliminate some of the bacteria clogging it, he said.”Cutting the stems when you get them is an important thing to do,” he said.Recutting the stems and changing the water daily will also help extend the life of roses, said Victoria Straw, owner of Victoria’s Flowers on High Street.”As (the roses) break down, there is bacteria building up and that is going to stop the water from flowing freely to the bloom,” Straw said.Roses should live for 12 to 14 days if they are recut while submerged in water every day, she said.”If they start to look a little droopy after a few days, cut them underwater and leave them totally submerged for about an hour,” she said.Fully submerging the flowers in cool water allows them to soak up the water through the pores in the bloom as well as through the stem, said Paula Fracasso, manager of University Flower Shop on 11th Avenue.”As long as your roses have a direct water source in the vase, there shouldn’t be a problem,” said Jill Kiely, owner of University Flower Shop.Keeping roses away from a direct heat source such as televisions will keep them from opening up quickly, Straw said.”It takes moisture out of the flowers and dries them out,” Kiely said.Household remedies such as putting pennies or aspirin in the vase are not helpful, Knee said.