Smart plants. There is genius in our roots

«Stand we know how to bend over for an instant over their humble work, we discover many traces of a shrewd and lively intelligence, not only in the seed and in the flower, but in the whole plant, stems, leaves, roots». It was 1907 when the Belgian poet Maurice Maeterlinck published the essay The intelligence of flowers (retold by Elliot, 2022). The author is not a botanist, but the examples that he reports in his agile booklet aim to demonstrate that there is “a widespread, general intelligence” that unites humans, animals and plants. Over a hundred years after Maeterlinck and after the enormous progress made by science, in what terms can we speak of the intelligence of flowers?

Are there intelligent plants?

“Intelligent” plants are one of the themes chosen by the 2023 edition of Orticola di Lombardia. Humanizing plants is not correct, just as it is not to think that they are insensitive just because they are different from us. Despite being firmly anchored to the ground, unable to move as animals do, plants are however capable of performing extraordinary feats, sometimes more “smart” than we humans would do. «When we speak of “intelligence”, this term presupposes a will: I behave in a certain way to achieve a certain result. A process that requires a central nervous system,” he explains Renato Bruni, director of the Botanical Garden of Parma. «Plants do not have a brain, but they are capable of responding to external stimuli through chemical processes».

Put simply, if a plant leans towards the sun, it doesn’t “decide” to do so, it is the information it receives from the outside that activates a biochemical reaction. «We tend to observe plants from an anthropocentric perspective» continues Bruni. “We say they’re intelligent because we like to see something similar to us in them. In reality, they are completely different, and this is a very fascinating reason. While not like us, they show efficient and wonderful solutions».

The flowers are hermaphroditic

Let’s start our journey with flowers, the most beautiful sexual organs in nature: fragrant, colorful, of infinite shapes. In most plants, they are hermaphrodites: the same flower includes the male and female component, plus nectar to attract pollinating insects which, while they feed, get dirty with pollen, carrying it from one flower to another. A solution to overcome the problem of not being able to move. Orchids – almost 30,000 species, capable of growing by the sea and at an altitude of 2,000 – are masters in attracting their pollinator. «The Ophrys, present in Europe, have modified a part of the flower, the labellum, to make it resemble the back of the female pollinator» explains Maria Grazia De Simoni, scientific director of the Italian Group of Spontaneous Orchids (Giros). «In addition to color and shape, they also simulate its hairiness. Furthermore, the plant even emits the same pheromone odor as the female.” The poor male insect can’t resist: he throws himself into the flower, with his head he bumps the pollen that remains clinging to him and when he goes away he takes it to another orchid, which will be fertilized. «Cypripedium calceolus or Venus’ slipper has a cup-shaped labellum, for the insect it is a sort of refuge» adds De Simoni. “Once he gets in, though, he can’t get out. There is only one path, very narrow, which forces him to pass close to the pollen sacs». A shower of pollen to take to another orchid is the price of freedom. Other orchids, like some Dactyloriza, have a strategy based on a food deception: the flowers resemble others rich in nectar, even though they lack it. The poor pollinator goes in to feast and comes out with an empty belly covered in pollen.

Plants know how to adapt to the environment

Another “sly” is the Victoria amazonia, a water lily coming precisely from the Amazon, with enormous leaves that can hold up to 45 kg of weight. The flowers are no less prodigious: when they open they are white, fragrant and warm, a magnet for the pollen-covered beetles that enter and deposit it on the female part, carrying out the fecundation. Twist: the flower suddenly closes and the beetle remains a prisoner until the following day. Meanwhile, the flower matures the male part and when it reopens the host flies away covered in more pollen. Shortly after, the white flower turns red: the signal that it has already been fertilized.

If it seems strange to you that one flower is female one day and male the next, that is nothing. In nature there are dioecious plants (with separate male and female individuals) and monoecious, with male and female flowers on the same plant. And then, there are fluid vegetables. «Arisaema triphyllum looks like a dark calla lily» explains Renato Bruni. “At first glance, the flowers all look the same, but they can be female one year, male the next. Nothing happens randomly: if the plant has experienced a favorable year and has strong and energetic roots, the flowers will be feminine. In fact, producing fruit implies an important energy cost. If, on the other hand, it has suffered and is weaker, it will produce male flowers. Thus it has more opportunity for the pollen to move away from an unfavorable place to produce seeds elsewhere”.

Plants are brilliant at sensing their surroundings and adjust their behaviors. There is also a Japanese fernsays Bruni, who, when she settles in new land, is female and releases a hormone into the soil which affects all the ferns that will grow around her. They will have to be male, in a reverse harem. So she will have on her side all the chances to reproduce at her best.

Intelligent plants: the trap of carnivores

They have inspired fantastic stories and video games. Giant carnivorous plants, capable of swallowing a man, are pure legend. In a smaller dimension, there are vegetables that have developed a particular survival strategy, finding themselves living in soils poor in nutrients. To obtain them, one becomes a hunter: one adapts oneself to catching insects.

«There Dionaea muscipulaor Venus Flytrap, is among the best known» explains Valerio Guidolin, nurseryman of Diflora and expert on carnivorous plants. «The two foliar lobes equipped with “teeth” have six sensory hairs inside, three on each side. A single touch does not lead to closure, but the second touch within a precise period of seconds causes the trap to close, not hermetically, but just enough not to let the insect come out for the nectar. This mechanism is to save energy: if the plant continued to open and close several times in vain, it would die exhausted. There Dionaea it also has a sort of timer: every 30/40 seconds, it restarts from zero. Once the insect has been caught, the production of digestive enzymes is triggered».

In Orticola there will also be sarracenie, in the shape of a tube. Do carnivores exist in nature here too? «Yes, for example the Drosera rotundifolia, even if the best known are American». The tricks of plants are endless. From the many ways to make seeds fly away with the wind (an example for all: the dandelion) to the ability of some climbers to identify a possible support thanks to a sensitivity to contact. For millions of years, they have learned to cope in the harshest conditions. Trees included.

An example? The Taxodium distichumor bald cypress, is a deciduous North American conifer that can be found near lakes or flooded land. To let the roots breathe, it has developed organs similar to woody stalagmites (pneumatophores) that protrude from the ground to bring oxygen to the submerged parts. «All the Taxodium they have this characteristic» he comments Renato Ronco, who will bring four varieties to Orticolaincluding the Mucronatum, or Montezuma cypress, the largest in the world in terms of trunk diameter. And also with the Taxodium distichum the atmosphere of the Montanelli Gardens in Milan will be that of an enchanted garden straight out of a fairy tale.

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