Weeds growing in poor city areas more nutritious than store-bought produce


Researchers find an unexploited and surprising wealth of free stuff growing in San Francisco’s “urban food deserts”. Natalie Parletta reports.


Hard times on the streets of San Francisco. The plants growing on the sidewalk, however, could be used to fill a critical nutrition gap.
Hard times on the streets of San Francisco. The plants growing on the sidewalk, however, could be used to fill a critical nutrition gap.
Diane Bentley Raymond / Getty Images

Despite the odds, nature does her best to nurture us. Researchers from the University of California, Berkeley, have reported finding nutritious wild greens growing abundantly in poor urban areas of San Francisco, even surviving record droughts.

The researchers, led by Philip Stark, collected the edible wild greens from three areas, each equivalent to nine city blocks, in disadvantaged neighbourhoods surrounded by busy roads and industrial zones. The areas, classified as “urban food deserts”, are more than one to one-and-a-half kilometres from the nearest shop that sells fresh produce.

Six different species were tested for nutrition content: chickweed (Stellaria media), dandelion (Taraxacum officinale), dock (Rumex crispus), mallow (Malva sylvestris), nasturtium (Tropaeolum majus) and oxalis (Oxalis pescaprae). All compared favourably to kale – arguably one of the most nutritious domesticated greens – for several nutrients.

The wild greens boasted more dietary fibre, protein, vitamin A, sodium, calcium, iron and vitamin K, and provided more energy. Kale’s vitamin C content outshone the species tested, but the researchers suspect other greens such wild mustard (Hirschfeldia incana) and wild radish (Raphanus raphanistrum) might rival it.

To date the investigators have documented 52 different species in the mean streets of San Francisco. Other abundant wild greens include cat’s ear (Hypochaeris radicata), fennel (Foeniculum vulgare), plantain (Plantago lanceolate), sow thistle (Sonchus oleraceus), wild lettuce (Lactuca ludoviciana) and wild onions (Allium spp).

“Even during this low-production period, almost every address in all three study areas had several servings of several different species, suggesting that wild edible greens are a reliable source of nutrition all year round,” write Stark’s team.

After rinsing in water, the plants had no detectable levels of pesticides, polychlorinated biphenyls (PCBs) or heavy metals – all toxic substances that might have been expected in local environments.

How can people detect if the wild-growing greens are edible? “Familiarity,” says Stark. “Most people have no trouble telling the difference between, say iceberg lettuce and romaine lettuce.”

He recommends that people wanting to try wild greens educate themselves and gradually add them to their dishes.

The report cites economic data that estimates the availability of waste-adjusted vegetables in the US as 1.72 cups per person each day, less than the recommended serving of two to three.

“Waste-adjusted availability is the sum of domestically produced vegetables and imports, less the waste that occurs throughout the food chain,” the researchers explain, suggesting that wild food could improve nutrient security by filling the gap.

They suggest that, “Wild foods might also contribute to a healthy ecosystem by building soil organic matter, retaining water and nutrients in the soil, and reducing erosion.”

What’s more, the wild plants could enrich biodiversity by providing a habitat for insects, animals and other plants.

The report is on the pre-print server bioRxiv and is thus still awaiting peer review.

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Natalie Parletta is a freelance science writer based in Australia.
  1. https://www.biorxiv.org/content/early/2018/08/06/385864
  2. https://www.inaturalist.org/projects/berkeley-open-source-food
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