June 2024

Urban wild plants: not really «weeds»

The urbanising process is one of the characteristics which define our society. According to the United Nations, between 1950 and 2018, the world´s urban population grew more than fourfold, from 0.8 million to 4.2 million. In Spain this transformation process, which started in the 1960s (with a boom in the 1980s), meant a rapid growth of the urban surface of cities, which was inevitably accompanied by the occupation of natural ecosystems, and the impoverishing, replacement, or transformation of their biodiversity. Almost 75% of the planet´s surface has been changed, pushing wildlife into an ever-decreasing corner and, according to the World Economic Forum, loss of biodiversity and the collapse of ecosystems are now the two biggest threats which humanity must face in the coming decade.

Even so, a city itself is a habitat for many species which are able to-exist with humans and their activities. We put plants in our streets, gardens or balconies, but other small plants spring up spontaneously alongside them, finding cracks in the pavement, tarmac, paving stones… They are usually not particularly pretty species, and they colonise these spaces despite the difficulty of surviving in an adverse environment. They are ephemeral plants (arvense, ruderal, spontaneous, adventitious, weeds…) which remain hidden most of the year but flourish suddenly in early spring or autumn, only to disappear in the summer and winter.

They are generally undervalued for being short-lived and modest, but also for their intensity, concentrated over a short space of time, which makes them difficult to control and domesticate. This is why we usually refer to them as «weeds», when they are really survivors, colonisers of a hostile environment like cities.

Many of these plants are the ancestors of our crops (Eruca vesicaria, a relative of rocket), immigrants from other continents (Eringeron bonariensis or fleabane, which comes from South America), food for insects (Malva sylvestris or common mallow, which is eaten by firebugs) and urban birds (cruciferous plants like Sysimbrium irium or London rocket, whose seeds are much appreciated by some species of birds), herbal remedies (Silybum marianum or milk thistle, which is currently used as liver protection), the remnants of wild nature in the city. They have a hard life because we persecute them, tread on them, cut them, grub them or spray them with poison. This makes them even less known to city-dwellers as it is difficult to see them and appreciate their characteristics.

One example of these species is the little dandelion (Taraxacum officinale), which has both medicinal and nutritional properties. It is an herbaceous plant from the Asteraceae or Compositae family. Its (edible) leaves are long, deep green and tender-looking. Its flowers are composite and yellow. Its fruit forms a round structure (cypsela) which is spread by the wind (few people have never blown at these to make their seeds float around in the air). 

Its leaves taste rather bitter and have traditionally been used for salads, in some parts of Spain the stalks are used to make infusions as a substitute for coffee. It is diuretic, anti-inflammatory and helps digestion (it is slightly laxative).

In our cities it grows on commons, in kerbs, flowerbeds, roadsides, around trees, in gaps in walls, etc. To use it, the leaves and shoots should be gathered when they are still young, before flowering (mainly in spring, although sometimes in other seasons). It is used in salads, after rinsing (it is important to check that dogs have not urinated on it…).

Such are its properties and uses that its seeds can be found in garden centres and nurseries for growing as food crops.

These plants should be seen as organisms which live with us rather than as a problem or muck, because they continue to benefit the urban population where they settle. Currently, questions are being asked about indiscriminate grubbing, and plots are being set aside in some parks in Madrid so that these plants can grow naturally free from weeding, grubbing and herbicides, which shows the value which is starting to be attached to these species.


José Borrell Brito, graduate in Biology from the Universidad Autónoma de Madrid (Spain), is a member of the Grupo Heliconia and expert in environmental education and the development of training and awareness programmes. He contributed to the Virtual Museum of Human Ecology with a piece in January 2019 called La diversidad de aves, indicador de calidad de vida en las ciudades (The diversity of birds as an indicator of quality of life in cities). Jose Ignacio Gómez Crespo, graduate in Environmental Studies from the Universidad de Alcalá (Spain), is a member of the Grupo Heliconia  and works in education, training and as an environmental volunteer.