Why do some flowers smell so nice?

Why do flowers smell? It’s not for our benefit, that’s for sure. It’s their way of enticing insects and birds to fertilise their flowers, with some using perfumes that the pollinators just can’t resist. Others specialise, in releasing scents that only appeal to a particular insect - the Soaptree yucca, for example, emits an aroma that attracts just a single species of yucca moth. As the pollinators travel from flower to flower, they collect and deposit pollen, fertilising the plants.

But some pollinators aren’t attracted to any particular scent or are attracted at different times and pollinate anyway regardless of scent or not, with some flowers are not being scented at all, or barely, which brings me to roses.

Wake up and smell the roses – maybe!

Some scented flowered plants may have been cultivated to enhance the sweet smell - and conversely some seem to have lost their scent: it’s sometimes said that many modern roses fall into the latter category. In fact, those really pretty cultivated roses - the ones from florists - I have noticed no longer smell, not that I get flowers on a regular basis to verify this! It is said that cultivating blooms with a focus on their visual attributes can leave scent traits disadvantaged.

Scientists have apparently isolated the gene and the proteins that are responsible for the odour of roses. This may be a troubling development, as now that the gene has been identified, it may only be a matter of time until some enterprising researcher leads the way for probiotics that make excrement smell like roses!

To pollinate or not to pollinate

Fascinatingly, once perfumed flowers have been pollinated, they tend to reduce their smell. This allows other unpollinated flowers a chance to attract a pollinator (how polite). Buds are less fragrant for similar reasons – they aren't yet ready for pollination. And some don’t even need a smell for pollination, as wind or water does the trick for them - grasses and some trees for example.

Some flowers attract nocturnal pollinators, and these are often strikingly scented at night – such as wisteria, honeysuckle and jasmine – and are often white, yellow, pale blue or pink.

But not all flowers smell nice!

Why do some plants smell so bad? It’s a form of communication for these plants. These smells are a combination of complex chemicals or volatile organic compounds that evaporate and spread through the air to lure pollinators and repel predators. Plants can have sweet fragrances and floral scents, herby and fresh scents - or a filthy stench.

The smell (and colour) is mainly to attract insects; but one or two plants actually smell foul to us - stinky Rafflesia or the Amorphophallus titanium, the corpse plant, for example.

Some lesser-known pollinators such as beetles and flies perform the same function for equally uncommon plants. Most of these plants bear fleshy flowers that are often covered with hair, essentially looking and smelling like decaying flesh to the pollinators. The scents attract insects that inadvertently pollinate the plants or sometimes even lay eggs in their smelly flowers.

The corpse flower holds the title of ‘the worst smelling flower in the world’ and it smells just like a rotting, stinking corpse. With their huge vase-like exterior that packs its smelly flowers inside, these blooms are huge draws at greenhouses all over the globe. The blooming of a corpse plant is a rare and special event, as most plants require seven to ten years to produce their first blooms and bloom only every four or five years thereafter.

So, we understand why flowers have smells. What I don’t get is why my appreciation of certain flowers is so similar to that of an insect. Why do both of us slow down to smell the roses? Well, roses are not only the flower of love but the ones that do smell can also vastly reduce your stress hormone adrenalin, so next time you get given a bouquet of roses it may be a bonanza for both your heart and your body – perhaps the pollinators got a bit of a ‘buzz’ too!

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan