Why do flowers smell so sweet

These days they are increasingly hanging out in the parks: the taster. Spellbound, they stop in front of a clump or a flower, bend over or stretch and then, somewhat embarrassed: they smell. A quiet, graceful process that seems hopelessly romantic to the observer - but also contagious. What is there to smell? How does nature actually smell? So sometimes you risk a nose. Nobody can say whether it smells the same.

The nose has a special role in the human sensory system. For Kant and other philosophers, smell was the "most dispensable" of all our senses - and this is how it initially appears, compared to the two cornerstones of our orientation, hearing and seeing. And yet olfactory is perhaps the sense that connects us most closely with the world. Smell is considered a "vital sense". Since he is bound to breathe, we always take our environment over the nose. Anyone walking past a slaughterhouse may hold their nose. But the stench penetrates through the mouth, so you know that it is there. The same applies to good smells, of course, which can currently be experienced everywhere: the fragrance cloud of a lilac bush lets us feel spring with every fiber - even if we don't see the plant at all.

It is believed that the fragrances of flowers originally developed from toxins

If you smell and rave about with full senses, you may find out how poor the usual descriptions of plant scents are. "Sweet", "flowery", "honey-like", "soapy", maybe a synesthesia like "sultry". Our language and thus our thinking does not provide much more. Nobody describes the charm of the fragrance of flowers, but also the inability to grasp it, as well as Marcel Proust in the first part of his novel "In Search of Lost Time": "But how long I stayed in front of the hawthorn bushes and their invisible and inhaled the smell standing in the air, they donated their constant and tireless, lavish abundance of their ever-identical magic, without, however, allowing me to penetrate deeper into it, similar to certain melodies that can be played a hundred times in succession, without at least any closer to their secret get."

There is a reason why this phenomenon can only be approached so delicately and cautiously. The scent of flowers is a highly complex language and, above all, one that is not addressed to us, but to the pollinators. But their relationship to the fragrance of flowers has also been anything but well researched. If you want to know what little there is to know about it, you have to go to Stefan Dötterl, Professor of Plant Ecology at the University of Salzburg. Like no other, he knows his way around - the natural scientist type: somewhat shaggy hair, full beard, functional jacket - with the complicated connections between plants and insects. "Up until the 1980s it was thought that visual stimuli, that is, the colorful flowers, played the main role in pollination. But then it was found that bees often only perceive the color of a flower from around 30 centimeters "says Dötterl.

Not all plant blossoms smell - this is above all a peculiarity of the opaque ones that have been around for 120 million years. With around 300,000 species, they dominate the plant kingdom. There are several reasons for that. For example the fact that the ovules are protected by the ovary. Another advantage of these plants is their invention of nectar. Other plants only offer pollen grains as a lure for pollinators - but the plant also needs them for reproduction. As soon as the insects fly to the area because of the luring nectar, pollination is more effective. And this is where the heady scent comes into play. "It is assumed that the flower scents originally developed from toxins that were supposed to protect the flower from predators. But then the plants that were visited by insects had a fitness advantage - and the deterrents developed attractants," explains Dötterl.

Exactly how communication with pollinators works has so far only been researched in individual cases; the first step is to break down the plant odor. To do this, insect sensors are wired to track exactly what the animals are actually reacting to. Unexpected mechanisms emerge, for example a native orchid like the broad-leaved stendril mimics the smell of injured grass leaves. How so? Because caterpillars usually nibble on leaves and the resulting smell attracts predators such as wasps. The orchid, on the other hand, uses the wasps that have been baited under the wrong pretext for pollination. It is only through such studies that one learns which substances actually smell, such as the sweet and fresh lilac aldehyde everywhere in cities. Or, one of the most common indigenous fragrances, the honey-like 2-phenylethyl alcohol. Or indole, which smells like feces in high concentrations, but is sweet and flowery in small doses.

Marcel Proust

"But no matter how long I paused in front of the hawthorn bushes and inhaled their invisible scent standing in the air, they donated their ever-same magic in constant and tireless, lavish abundance, but without allowing me to penetrate deeper into it."

Even if the scent of flowers remains a secret, we can do a lot with it

Professor Dötterl has also learned that the human nose is actually not made to understand this language: "When we break down the fragrances of flowers in the gas chromatograph, I sometimes hold my nose to the separation column and sniff the individual components. And very often I lie down wrong with my assumptions about what smells. " But even the scientist you can tell that he is still addressed in a very emotional way by the scent. While strolling through the Salzburg Botanical Garden, he stops almost indignantly and shouts: "What? You don't know how the flowers of the sallow willow smell? That is so wonderful!" Or: "Have you never smelled the mistletoe flowers? They are tiny and smell of freshly squeezed passion fruit juice."

Even if the scent of flowers ultimately has to remain a secret for us, we can do a lot with this secret. Or better: it reaches deep inside us. Again it was Marcel Proust who described the connection between the sense of smell and taste and human memory. In the first part of the "Search for Lost Time", the aroma of linden blossom tea sucks the narrator directly into a childhood scenario. For Proust, deliberate memory only creates hollow illusions, because we only remember what we consider important. The mémoire involontaire, however, which hits us like lightning with a scent, creates situations of extreme presence. The fact that this condition is triggered by 2-phenylethyl alcohol in the case of linden blossoms is of course poetically irrelevant. But maybe that's why spring with its scent is such a positive experience for many people: The smell of the flowers in the streets reminds us of earlier years and of what happened back then.

That leads to the next point: As a rule, we do not perceive our fellow human beings primarily through smell. Unless they stink. Or it is a loved one that we come close to. Perfumes expand the radius of smellability by a few meters and are sold as an increase in attractiveness. That's right - in every act of smelling a sexual chord vibrates softly but noticeably. For plants, flowers are sexual organs, and we too participate in this aura. Although we are not meant by their scent at all.

What blooms when A calendar

Lilac. April to June

One of the most showy native flowering plants. Very robust, likes to grow extensively. In many subspecies that have white and pink to dark purple flowers. Lilac aldehyde, which is mainly responsible for the fragrance, was one of the floral fragrance substances that was isolated in its pure form.

Elder. May and June

Until the modern age, myths grew up around the bush. If children were placed in a cradle made of elder wood, they could be fetched by Mrs. Holle. The scent of the flowers is sharp and sweet and, according to the ancient doctor Galen, similar to that of sperm.

Linden tree. May to June

Until the 19th century there was a village linden tree in every village. A special form of it is the "Tanzlinde", which is artfully framed and curved. Summer linden trees in particular have a strong smell. The smell is mainly released in the evening and at night.

Black locust. June and July

Often called acacia, which is wrong. The robinia or false acacia comes from North America, is very frugal and therefore a popular street tree. The flowers smell very sweet, like a slightly slutty perfume.

Rose. April to October

Since 2000 BC at the latest Chr. Roses are grown in China and the Orient. The Greeks dedicated them to Aphrodite, the goddess of love, and Dionysus, the god of intoxication. The wild forms also have a strong smell. The substance rose oxide is primarily responsible for this.

Ivy, flowering: September, October

In autumn hundreds of still living bees cavort in the ivy. The reason for this is the yellow, hedgehog-like flowers that have a strong scent. Their smell is reminiscent of flowering fruit trees, but mixes with the pungent green scent of leaves.

And then there is a completely different and yet related dimension that we can sniff out: life itself. Flowers have a strongly ephemeral nature and are quickly ephemeral. Often a plant, such as the evening primrose, only blooms for a single night, then the petals are blown in the wind. It is similar with animal pollinators. As early as July, dead bees and bumblebees can be found en masse under linden trees. The scent of the late blooming Crimean and silver linden attracts them, but they have done their duty for the survival of their people. They are allowed to suck nectar for a few hours, then they fall dead to the ground.

For us, the short life of the blooming splendor is an enormous waste - all flower cultivations therefore try to lengthen the flowering phase beyond what is biologically necessary. But what seems wasteful to us is only reproductive efficiency. Nature does not allow itself to be sentimental. That is reserved for us when we realize that in life we ​​experience at best 80 or 90 hawthorn blossoms sensually. Every time you sniff a spring blossom is a reminder of your own clock of life.

The good thing is that spring and its scents also have the power to brush that thought aside. You just have to stop and smell.