Roses are the darling of the flower world. These plants were considered so majestic by the Ancient Greeks, that they named it the queen of all flowers. But while roses grab a lot of attention, they are also known as a notoriously fickle plant. By contrast, carnations are a hearty plant with blooms that last much longer than roses.
Even as cut flowers, carnations can last up to two weeks, which is much longer than roses. The reason that carnations last longer is simply genetic. Cut flowers are still living flowers, and still contain the same traits as their rooted counterparts. In nature, carnation blooms stay vibrant longer than rose blooms do.
Part of the reason that rose blooms fade faster than carnations is that they use more energy. If you were to take cut roses and carnations and place them in separate vases, the roses would require a solution of floral preservative while the carnations would do well without the preservative. In nature, rose bushes are heavy feeding plants that require lots of nutrients from fertilizer. Carnations may last longer simply because they require fewer nutrients.
Because carnations have been bred for a stouter stem, the blooms are less prone to suffering from 'bent neck' than roses are. The stem of a flower is like a straw, drawing nutrients and water up to the flower. When the stem becomes blocked with air bubbles, the stem becomes soft and the flowers bend over. Unless the stem is cut shorter to remove the air bubble, the flower quickly wilts. Some florists use floral tape and wire to prop up flowers and prevent bent neck.
In addition to nutrients, roses also need more tightly-controlled temperature ranges to survive. Once roses are cut, they are kept in refrigerators to keep them fresh, much like produce. Much like Iceberg lettuce that has been left on a hot kitchen counter, once cut roses are taken out of these refrigerators they quickly wilt. By contrast, carnations are hearty enough that they can bring winter-color to gardens in the extreme southern growing zones of the United States.
Another reason that roses may wilt faster than carnations is that they travel farther before being purchased. Most commercially grown roses are raised in equatorial climates at high altitudes and then shipped to florists outside these tropical locations. Although these roses are shipped by air to their destination, there is still a little plant degradation during the shipping process. More expensive roses wilt more slowly because they have been cut most recently. Meanwhile, there are many carnation nurseries in the United States. Foreign nurseries often send carnations to the United States via ship.