Is the weed born or made?

Few study groups within ecology and agriculture are baptized with a term as strong and negative as weeds . When I talk about the object of our work with friends, we do not miss the quick response by saying proverb: “weed never dies”. Even sometimes the most focused request the magic potion that ends with those annoying little plants that invade their neighborhood garden.

In the definitions given by the experts, the subjective and anthropocentric nature of the concept is clear. The Spanish Society of Malherbology (SEMh), define weeds as ” any plant or vegetation that interferes with the objectives or needs of man” . Therefore, in addition to orchards and crops, we place the weed blocking roads and ditches or spoiling the lawn of any sports facility. The characteristics that define these pioneer plants are having more than one life cycle per year, underground organs with which to regenerate, very high production of seeds , rapid growth and early flowering … The number of ‘skills’ present depends on whether we are faced with a plant with high potential as a weed.

Of the 250,000 plant species that exist, it is estimated that 3% act as weeds . Thus, although it may seem that any species has the potential to interfere with our interests, the reality is that there are characteristics that predispose this 3% to manifest pernicious behavior. We could translate more than a score of these physiological attributes into a single ecological feature: the ability to colonize and develop successfully in disturbed habitats . Do not forget that our protagonists were here long before there were crops, roads, ditches and football fields. We have simply put within their reach environments with a strong anthropization that favor their colonizing character.So, a weed is so as it affects the human being, without being something intrinsic to the biology of the plant. In fact, species classified as weeds and that can cause losses in orchards and crops, such as borage ( Borago officinalis ), are both regularly cultivated for consumption. And we go further. According to The world’s worst weeds -something as well as the bible of harmful species for agriculture-, in the top ten of weeds, we find the purslane ( Portulaca oleracea ), which is common in Portuguese greengrocers .The most paradoxical case occurs when a species of crop already harvested, for example a barley, is presented as unwanted grass in another subsequent crop on the same land. This situation is designated by the term ‘ricio’ . Could we deduce therefore that barley in this case is a weed? Yes, definitely.

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The bad-good herbsIt seems a contradiction to try to highlight positive aspects of something that is qualified as bad in its denomination, that is why we should refer to this vegetable group with a term without pejorative load: weed plants . Protect the soil from compaction and erosion, serve as habitat to natural enemies of pests , favor the presence of pollinators , be used for medicinal and nutritional purposes are some of its benefits, in addition to its undoubted landscape and social value. How would Van Gogh have painted ‘Field of wheat with crows’ or Monet his ‘Poppies’?In addition, the presence of weeds contributes to biodiversity and ecological balance . Many times it has been the human being himself, in his eagerness to turn the fields into intensive factories of food production, which has created the ‘monster’ of the weed, causing the irruption of species difficult to control because of the elimination of companion species that exercised control over those.From this point of view, we have begun to become aware of the need for legal protection over weed communities. In its 1994 Action Plan for Biodiversity, Great Britain has already established Cereal field margin hap as one of its 46 priority habitats, defined as “swaths of land between cereal crops and the boundary with the countryside, extending within the cultivation in a specific distance, managed to favor the species under conservation “. Not everything will be panda bears and inaccessible flowers of remote peaks in conservation.*   José Manuel Martín is a technician in the Department of Plant Protection of the Institute of Agrarian Sciences (ICA) of the CSIC.Tags: agricultural sciences, CSIC Divulga, scientific culture, Institute of Agricultural Sciences, weeds | Stored in: Biology, Earth Sciences.