Weeds as a source for human consumption


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Weeds as a future source for human consumption.

Martha Díaz-Betancourt1, Ismael R. López-Moreno1, Eduardo H. Rapoport2, Luciana Ghermandi2 , Estela Raffaele2 and Ana Ladio2.
1. Instituto de Ecología, Ap. Postal 63, Coatepec, Veracruz, Mexico.
2. Universidad Nacional del Comahue, Departamento de Ecología, 8400 Bariloche, Argentina and CONICET


Weeds may constitute an additional food source for humans. Up to 66% of weed species are edible and abound in urban and agricultural environments. A total of 43 species were sampled in tropical areas in Coatepec Mexico (e.g. roadsides, urban vacant lots, streets, sugar cane and coffee plantations). A similar survey performed in a temperate area in Bariloche Argentina with 32 species sampled. At a greater geographic scale, a comparison between Mexican and Argentine weeds shows that, proportionately, the food parts vary a little between regions. In general, the uses go from leaves, seeds, roots, fruits, and flowers.


Las malezas puedens constituir un recurso de alimento para el hombre. Arriba del 66% de las especies de malezas pueden ser comestibles y son abundan en ambientes urbanos y rurales. En total se recolectaron 43 especies en en áreas tropicales de Coatepec (rutas, terrenos baldíos, calles y plantaciones). Un recurso similar se encontró en una área templada de Bariloche, Argentina con 32 especies. En ambos lugares, el aprovechamiento, fue de hojas, semillas, raíces, frutos y flores.

According to FAO’s Production Yearbooks, developed countries, and especially urban populations, began to depend almost entirely on the extensive and intensive agricultural production of merely 100 food plants. Since the Paleolithic plants have sustained the hunting and gathering peoples since the invention of agriculture, in the Neolithic the prevailing knowledge about edible species began to be lost. Two well-preserved mummies found in Denmark provided interesting information on food habits during the Iron Age. Meals contained a diet much more diversified than that of modern man with 66 different plant taxa (Godwin 1960; King 1966). Still part of the old tradition is maintaining in some eastern Asian and Latin American countries. In Korean local markets 112 wild plants are sold at prices higher than those of cultivated species and eleven species (some of them “weeds”) are exported to the U.S.A. and used to prepare Korean and Chinese typical dishes (Pemberton and Lee 1996). Similarly, Moroccan weeds are exported with the same purpose to the U.S.A., Spain, Italy and Greece (Tanji and Nassif 1995) and more than 20 “weeds” are also cultivated in Mexico (Linares and Aguirre 1992). Edible weeds, however, are scarcely used in many countries, and weed gathering is more of a weekend hobby than a regular source of food supply. Common weeds prove to be an interesting resource in small to large cities where they may provide supplementary food. Roughly, ten percent of the 260,000 known vascular species of the world should be considered as a potential source for human consumption.

In our study the majority of the sampled species appear in Kunkel’s (1984) list of food plants, to which we added Osmorhiza chilensis, from Argentina, and Drymaria gracilis, Galinsoga quadriradiata, Hydrocotyle bonariensis, Hydrocotyle mexicana, Margaranthus sulphureus, Oxalis latifolia, Sida glabra, S.spinosa, and Tripogandra serrulata from Mexico.

We have recorded 43 species in Coatepec and 32 species in Bariloche (see species list). These plants are commonly consumed by people and were repeatedly tasted by us. They represent, however, a small fraction of the real richness in both areas. More than 24 % of the 700 weeds listed in Mexico by Anonymous (1991) are edible and of the 320 exotic weeds recorded in northwestern Patagonia (Rapoport and Brión 1991), 90 species (28 %) are edible. Annuals show a greater proportion of edible leaves and seeds than perennials. While perennials show a higher proportion of edible roots (including tubers or rhizomes) than annuals.

The proportion of edible plants increases considerably in anthropic environments, especially in weed communities. Our data showed that edible, non-weedy plants comprise between 6 and 21 percent of the biomass of the natural communities surveyed. It is probably not by mere chance that the majority of the centers of origin or domestication of cultivated plants proposed by Vavilov (1938) corresponded to ancient, sedentary cultures. Since edible plants abound everywhere, it seems that civilizations developed in any environment where for historical reasons, people had time enough to exploit their natural resources in a more permanent and intensive way. The idea that civilizations arose in areas with abundant edible plants adequate for culturing is probably incorrect. The economic incentive provided by the revival of ancient gastronomic traditions persuaded some private entrepreneurs to change from the occasional gathering to a more permanent cultivation of “weeds”. Popular markets in Mexico (Linares and Aguirre 1992) and Korea (Pemberton and Lee 1990) offer a variety of gourmet “weeds” at higher prices than the common vegetables. By selection, plants originally wild, began to be more productive and adequate for human consumption. Rye, oats, carrots and several other cultivated plants originated as weeds, a fact that gives a clear idea of the enormous potential of weeds and other wild non-weedy plants as a source for new cultures.

A case of human-livestock-plant mutualism is mentioned by Kuznar (1993), especially referred to species of Chenopodium proliferating in unusual concentrations in corrals. Herd animals transport these forage species to pastoral campsites where the plants thrive in the organic corral soils. This creates a mutually beneficial relationship where certain plant species become camp followers of pastoral campsites. This is the process by which plant invaders reach the status of weeds first and, later on, the status of cultivars, according to Vavilov (1938). And this process may explain the fact that the majority of the most aggressive and cosmopolitan weeds are edible. Our results show that in anthropic habitats there are immense amounts of edible plants which are not always totally profited from. This is clearly evident in Argentina where people have almost lost the ancient practice of gathering wild food plants. In a tropical area such as Coatepec, the overall ‘standing crop’ averages 2.1 tons/ha whilst in temperate Bariloche it reaches 1.3 tons/ha. And tropical weeds are richer in species number and more productive than temperate weeds.

Because a significant sector of the Argentine population suffers from serious problems of malnutrition, the Universidad del Comahue and Municipalidad de Bariloche published a booklet (Rapoport et al. 1997) illustrating the 20 most common edible weeds. Free copies were distributed in provincial public schools. This instruction manual represents the beginning of a program which hopes to restore, at least partially, our ancestors’ knowledge. As a result of this printed information and a television program, a substantial increment of popular awareness and utilization of this resource, was registered.

List of Weeds Recorded in Coatepec Mexico:
Acalypha wilkesiana Amaranthus dubius Amaranthus hybridus Amaranthus spinosus
Anagallis arvensis Bidens odorata Brassica rapa Canna indica
Chenopodium ambrosioides Commelina diffusa Commelina erecta Drymaria cordata
Drymaria gracilis Galinsoga quadriradiata Heliconia caribaea Hydrocotyle bonariensis
Hydrocotyle mexicana Ipomoea purpurea Ipomoea tilliacea Ipomoea triloba
Margaranthus sulphureus Oxalis corniculata Oxalis latifolia Phaseolus vulgaris
Piper auritum Plantago hirtella Plantago lanceolata Portulaca oleracea
Rumex obtusifolius Sida acuta Sida glabra Sida rhombifolia
Sida spinosa Solanum nigrum Sonchus oleraceus Spilanthes americana
Tagetes micrantha Taraxacum officinale Tradescantia fluminensis Trifolium repens
Tripogandra serrulata Xanthosoma robustum Youngia japonica

List of Weeds Recorded in Bariloche, Argentina:

Alstroemeria aurea Berberis buxifolia Brassica rapa Cichorius intybus
Cirsium vulgare Claytonia perfoliata Cytisus scoparius Chenopodium album
Chrysanthemum leucanthemum Hypochoeris radicata Lactuca serriola Malus sylvestris
Medicago lupulina Melilotus albus Mentha spp. Oenothera odorata
Osmorhiza chilensis Papaver rhoeas Plantago lanceolata Rumex acetosella
Rumex longifolius Sanguisorba minor Silybum marianum Sonchus asper
Sonchus oleraceus Stellaria media Taraxacum officinale Tragopogon dubius
Trifolium repens

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