The thistle is always the first to return

Weeds are undesirables. But for some they are also the nucleus of a utopia, just as if there were good and evil plants, as if weeds were political. With their round, light-purple blossoms, thistles, for example, are beautiful to behold, but evolution has equipped them with chalky spines to protect the plants against predators. The dryer the climate, the more spines the plants have. Biennial thistles offer bees an especially great amount of nectar, provide seeds for birds, and leaves on which butterfly larvae feel at home. Many types of thistles, such as the Cirsium vulgare, which is native to Europe and Asia, spread far beyond their original habitat and displace other species.

Thistles are classified as pioneers, as so-called ruderal species, derived from the Latin rudus, which roughly translates as rubble. This is a bit misleading, as the classification simply means that the thistle grows where an ecosystem has been destroyed, and that may be an entirely natural occurrence – for example, on a mountain slope after a volcanic eruption or after a forest fire. Moreover, they flourish where the soil is rich in iron, phosphates, and nitrogen. Where there is nothing left, the thistle is always the first to return.

Ruderal plants grow wherever nature was destroyed by humans, or so biologist Carl Linnaeus observed in his “Systema Naturae”. That was back in 1758, meaning before the world was industrialized. A few years on, and fragments and ruins congealed in art to form images and stories of melancholy and past grandeur. Where there are ruins, weeds will not be far away. In 1796, Frenchman Hubert Robert painted buildings that were still standing, such as the Louvre in Paris, in decay, and, next to broken vases and people in strangely antiquated robes, a crown of thickets symbolizes the aestheticized decline. A little later, German historian Ferdinand Gregorovius described the Colosseum in Rome as a stone vase, as here shrubs grew that were otherwise not to be found anywhere in Italy – presumably because the seeds were introduced by animals from Africa that were forced to fight in the arena. Weeds are more than just cosmetic; they are also a sign of places that have wistfully been half-forgotten.

That said, soon there was no place left for rampant wild growth in the cities and gardens of Modernity. Apparently, in the 19th century the Paris municipal administration had lichen stripped off trees. Leipzig medical doctor Daniel Gottlob Moritz Schreber not only wanted weed-free allotment gardens but also a new type of human, made healthy and virtuous by ample time out in the fresh air. Controlling weeds became the task of gardeners, urban planners, and in the case of Schreber the object of a moral mission. Of course, the task was an impossible one, as plants are resilient and endure extreme heat and cold, dry and wet periods.