It is the time of Onam, the harvest festival in Kerala, India. The festival Onam is synonymous with floral rangolis or patterns meticulously arranged in front of the house to welcome King Mahabali. Colors and scents of flowers welcome the little girls 
and young ladies who go around the garden plucking flowers for this activity. It’s a rejuvenating walk through the garden breathing in the fragrance of the flowers. Ever wondered why and how flowers have this nice fragrance around them? Let us try and understand it.
Flowers use scent and colors to attract pollinators, (the bugs and other creepy crawlies you find amidst the flowers) who in turn help the flowers by spreading the pollen and aid in communication among plants. Night-blooming flowers have scents that attract bats and other nocturnal insects which help in their pollination.
The fragrance of a flower is an announcement that the plant makes to nature stating that it is ready to be pollinated and fertilized. Plants have this awesome sense of camaraderie as well, for in some 
plants once a flower is pollinated, it stops releasing fragrance or its scent changes such that it no longer lures an insect but passes on the chance to other unpollinated flowers.
What makes the flowers smell so divine? There are small molecules in the flowers of such plants, called Volatile Organic Compounds (VOC) which are called so since they evaporate very readily and thus present themselves as floral scent molecules that can easily get transported to the nose or equivalent parts in insects. These odorants are of three major classes:
- Terpenoids
- Fatty acid derivatives
- Benzenoids
The terpenoids and benzenoids are primarily present in the flowers and petals while the fatty acid derivatives are also present in the other leafy parts of plants thus contributing to the leafy odors. These VOCs are produced by petals and other parts of the plant but in some plants like orchids, there are special scent glands that produce the same.
Not only do flowers produce these molecules to attract pollinators but they also have a tightly regulated schedule as to when these molecules have to be emitted to attract maximum insects. For eg, flowers which are pollinated by bees release 
scent maximally around noon when bees are more active, night-blooming flowers release the scent in the night, etc. so as to ensure there is a peak in the release of these molecules around the time when there is the maximum probability of activity of the pollinators.
Flowers also release scent to deter the activity of predators like herbivores and to lure insects to devour them in the case of insectivorous (insect-eating) plants. Flowers fine-tune the composition of their odor packages so as to increase visits by pollinators while at the same time ensuring that predators are discouraged. Not all flowers have good scent…The rafflesia or carrion flower emits the odor of rotting meat which attracts the flies that pollinate it. The sulfur atoms in the VOCs of Rafflesia are responsible for the unique stink that emanates from it. It may be wise to steer clear of them so as not to be hit by the repulsive odor of such flowers.
Some flowers do not have any odor but they compensate for the lack of attractive scents by having bright big flowers to attract birds and other pollinators that are not dependent on fragrances.
These VOCs are isolated and characterized and used in the perfume industry, which is why one can just get transported to a garden of fragrant flowers just by one spray of floral perfume in one’s room. They are also extensively used in aromatherapy to heal the body and mind by fragrances.
The next time you breathe in the fragrance of your favorite flower, remember why it is fragrant, and with this knowledge enjoy the scent a bit more…Till then like Martha Hoffman
“I would sing of the roses
Their fragrance, their color, their form;
The beautiful fragrant storm
Of petals, dainty rose petals…”
Here are some links if you wish to read more
https://www.floweraura.com/blog/why-do-flowers-have-smell
https://scienceline.org/2013/01/making-scents-the-aromatic-world-of-flowers/
https://www.scientificamerican.com/article/why-do-flowers-have-scent/
For those who wish to know more about the Onam Festival here is a link for a bonus read
https://en.wikipedia.org/wiki/Onam
Let us know you more:
Which is your favorite flower scent? Type in your responses in the comments section.
