A Predetermined Lifespan
Like all life on this planet, flowers--no matter how lovely or vigorous--will eventually begin to decay. How fast a flower decays depends on a number of factors. The type of flower, the amount of water the flower receives, how the flower has been pollinated, temperature and other dynamics, can all impact rate of decay.
The process of flower decay, or aging in general, is called senescence. Vital cells and tissues begin to deteriorate, all because genetic encoding passed on to the embryonic plant has predetermined the duration of its life.
Certain actions can prolong the life of a flower, but the decay process is inevitable. A surprising amount of research has been conducted on flower senescence, since a plant's flowers die at a relatively fast pace.
Stages of Decay
The life of a flower begins during the bud stage. The bud gradually expands until it is partially open. It continues to expand until the bloom has opened fully. Not long afterward---hours or even minutes---the vibrant color of the flower begins to fade.
During the fading stage, the flower starts to lose turgor, a decrease in moisture and vigor within the petal's cells. Cell respiration slows. The flower wilts and begins a slow collapse. Proteins and nucleic acids are lost. Wilted petals may glisten with fluid that has been released from dying cells. Petals and other parts of the flower drop; eventually, the seeds at the base of the dead flower head are ready to be dispersed.
Slowing the Rate of Decay
Some flowers last only a day; others can live for several, even many, days. External factors for flower decay can be manipulated so that the bloom of a flower can be enjoyed for as long as possible. To promote longer blooms in gladiolas, for instance, snap off the topmost unopened bud, so that the lowest buds on the stalk will have a chance to open.
Place cut roses in cool water, not warm, unless you want to encourage blooms to open. For mums, azaleas and rhododendrons, scrape and split the stems before placing in water. Cut tulips require lots of water. Ensure that vases are clean and bacteria-free. Wounds on flower stems can promote bacteria growth, so select healthy, disease-free flowers for display.
The process of flower decay is a natural and necessary one in order for seeds to be released. Pollination may actually be one of the triggers for a flower to begin its decline, promoting the endless cycle of life and death in a flower.