A flower's fragrance is all about reproduction. The fragrance attracts insects and animals, and it tempts them to enter the bloom. When the insect or animal ventures into the bloom, some of that flower's pollen rubs off. When the insect or animal goes into another bloom of the same species, it leaves behind the pollen of the previous flower. The pollen fertilizes the new flower's eggs.
Why Flowers Smell
Once the flower is fertilized or pollinated, that flower's fragrance decreases. This allows flowers that have yet to be pollinated to be more attractive to pollinators. The fertilized flower's petals fade and are replaced by the ripening seed pod.
For the pollinators, the flower's fragrance signals food or mimics the pheromones of female insects. By attracting pollinators, the flower's fragrance can increase the pollinators' breeding and foraging efficiency. Some flowers only have scent during the day, but others release their fragrances exclusively at night. Flowers that attract bees, birds and butterflies have a sweet scent while flowers pollinated by beetles and moths have a muskier or fruity odor.
What We Are Smelling
A flower's fragrance is made up of volatile chemicals produced in sacs in the flower. These chemicals evaporate in the air and produce scent. Each species of flower has its own scent. Within that species, each flower has its own unique scent.
Late morning or early afternoon on a sunny day is the best time to fully experience the fragrance of flowers pollinated by bees and butterflies. As the sun warms the blossoms, the scent is released.
Early evening--just before dusk--is the best time to experience the fragrance of night blooming flowers. The dropping temperature and low light levels stimulate the blooms of night blooming flowers to release fragrance.
Cut flowers will begin to lose their scent two to three days after cutting; however, keeping cut flowers in a cool room and out of direct sunlight will prolong their fragrance.
Using the Frangrance of Flowers.
Flower fragrances have been used for centuries to perfume houses, clothing and ourselves. Some flower fragrances are so complex--and are made up of so many compounds--that scientists have not been able to synthesize them. A distilled fragrance is called an essential oil or volatile oil. It is made from flowers, leaves, stems and roots of plants, and sometimes the musk glands of animals.
Today, most essential or volatile oils are synthetic. Synthetics last longer, and their fragrance is more uniform. Making a scented item is more than imbuing a liquid with the scent of a single species. For example, a lilac-scented product might contain compounds found in roses, lilies and geraniums.
Billions of dollars are spent each year by companies trying to identify the compounds found in the fragrance of flowers. These compounds will be used in to make perfumes or to clarify a scent already on the market.