The biomechanical marvel of dandelions reveals a new kind of flight

Who hasn’t blown their seeds away, playing on the early spring meadows? This was the question with which I opened a small digression together with those who follow me on the social forums.

In front of the globes produced by the dandelionwhat we commonly call showerhead, everyone goes back to being a child for a moment; but perhaps it is worth emphasizing here too how even the product of what gardeners, horticulturists and farmers rightly consider a weed, in fact, as soon as it is observed with an eye free from prejudice and by applying scientific thought, it can become a source of inspiration for the future.

Even with the readers of this page it is worth going over a little reasoning, to show, in one, how the marvelous machine of Darwinian evolution produces astonishing adaptations and where curiosity can lead, if supported by scientific analysis.

Let’s start with the latter, curiosity. How does the seed of a dandelion fly, and how can it, in some particular cases, reach over 100 km from the mother plant?

This question was only answered in 2018, when the mechanism of the flight of dandelion seeds, which are technically called pappi, was fully described. This is a new and never-before-observed mechanism (although probably common in the natural world), as reported in an article published in Nature.

Meanwhile, the particular aerodynamic “porous” structure of the pappi, with about 100 filaments so thin that they occupy only 10 percent of the total space constituted by the circle in which they radiate, compared to a solid structure such as a parachute of about the same size, is four times more efficient at creating resistance against gravity.

But more importantly, and really new, is that this structure of radial bristles generates a pair of stationary vortices above the seed, which the scientists have highlighted through high-speed photography, illuminating the pappi with laser light under a stream of air and in the presence of smoke.

It is this very particular fluid dynamic structure that supports the flight of the seeds, for distances which in calm and dry air can occasionally be very large in the presence of a more or less sustained gust of wind.

Not only that: following the description of this mechanism, it was discovered that the number of filaments of the pappus is such as to reach the optimum porosity of the tiny parachute (around 90%) to maximize the aerodynamic effects described, and always this same number it is also optimal to ensure maximum flight stability.

In short: the dandelion, and the pappi attached to it, are a biomechanical marvel of nature, the study of which has led to the identification of a new type of flight.

But that’s not all: the microscopic structure of the shower heads can be used for traps capable of capturing dew, because in humid air the condensation is deposited with high efficiency on radial filamentary structures of the right material. Regardless of how we could use this adaptation, in the case of the shower head, the moisture trapping effect has a precise function.

In fact, in the presence of humid air, it is difficult for the seeds to travel long distances in flight, both because they are weighed down and because in those conditions the type of light breeze characteristic of drier conditions is less frequent. As has just been published, each pappus, responding to humidity, changes shape, “closing” like an umbrella turned inside out by the wind; that way, it’s more difficult for an accidental breeze to knock it off the head in atmospheric conditions where it couldn’t go too far.

In the same way, when it is flying, encountering humid air, it changes shape, losing the aerodynamic properties discussed before and falling to the ground, coincidentally in a humid place and therefore potentially suitable for germination.

The past five years have revolutionized our understanding of the mechanics and flight biology of seeds dispersed by dandelion dandelions; it might seem that this knowledge is just the useless product of the innate curiosity of physicists and other scientists, but in reality the first applications are already on the way.

For example, small probes released on Mars could use that planet’s winds to travel, exposing pappi-like structures so as to be dispersed without energy costs; while swarms of microscopic pappus-shaped sensors, powered by small solar panels, could be used for climate monitoring, traffic monitoring or in harsh environments.

Millions of years of blind evolution have produced that perfected flight structure we observe in dandelions; a few decades of scientific study have found the laws that have sculpted its structure and function, and perhaps it won’t be long before some of our machines will fly, hanging from the pops of an artificial dandelion.

This is how evolution works, this is how science proceeds, by chance, necessity and curiosity.