Can Urban Soil Offer Edible Weeds Fit for Foraging?

Researcher Philip Stark says yes, and touts the benefits to the body—and the prospect of better biodiversity.



Passersby may see them as weeds, but common urban plants including chickweed, cat’s ear, dandelion, sourgrass, and nasturtium are also healthy, nutritious foods. And for the past several years, researchers at the Berkeley Open Source Food project have marveled at the abundance of wild foods like these growing in urban environments.

They have documented the prevalence of edible plants, particularly in underserved communities with few grocery stores and limited access to fresh fruit and vegetables. The researchers have also been evangelizing the wide-ranging benefits of foraging, which include improving food security and environmental sustainability.

Philip Stark

Philip Stark

“When I see these plants, I see a lot of wasted nutrition and deliciousness,” says Philip Stark, a U.C. Berkeley statistics professor and the lead researcher of a new report, “Open-Source Food: Nutrition, Toxicology, and Availability of Wild Edible Greens in the East Bay.” “I see missed culinary opportunity, and I see missed opportunity to reduce the carbon and water footprint of our diets.”

The study offers evidence of the rich nutrition of urban weeds, and a reassurance that—at least in some cases—the plants are safe to eat even when the soil is suspect.

Stark recently talked to Civil Eats about the report, cultural and public policy barriers to foraging, and how farmers can help introduce these plants into our diets. An edited transcript of the conversation follows.

Your latest research examined the nutrition and safety of a half-dozen common edible weeds, all growing within arm’s reach of a public sidewalk or road—despite a lack of intentional watering or cultivation. What did you find?

The nutritional density of these plants is just incredibly high compared to cultivated crops that we think of as being nutritious, like kale and spinach. They were extremely high in iron, fiber, polyphenols, and all kinds of things that you’d like to be eating.

The happy surprise is that even in areas that have a history of industrial land use and where the soil is challenged with heavy metals, the plants were not accumulating the heavy metals in their tissues. Simply rinsing them with water, as if you were going to make a salad, was enough to make them safe to eat. There were also no detectable levels of PCBs or herbicides, including glyphosate, in our tests on the plant tissues.

Were you surprised by those results?

It’s folk wisdom that edible weeds are more nutritious than their domesticated counterparts. A lot of commercially produced crops have been bred for mildness in flavor, and a lot of the phytochemicals and micronutrients have strong tastes. So selective breeding [for less-bitter, milder tasting food] is somewhat responsible for breeding nutrition out of our food.

edible weed Bristly Oxtongue

Bristly Oxtongue.

In terms of nutritional density, one exception was that kale had more vitamin C [than the six plants tested]. I suspect if we had tested something in the same family—wild mustards and other brassicas in the area—they might have come out similarly on the vitamin C scale.

There were some particular surprises like mallow, a common non-native invasive [weed], which is as high in calcium as milk. If you have vegan friends looking for a calcium supplement, there’s a possibility.

You collected a half-dozen species in a few neighborhoods in the San Francisco Bay Area. Are there broader implications for other regions and species of plants?

It’s too early to make a general recommendation—the species of plant matters, the soil chemistry matters, the particular contaminants that might be in the soil could matter. But the results are concordant with work on urban foraged foods done in Germany, Italy, and Boston.

There certainly are plants that do concentrate nasty things from their growing environment. You don’t want to eat watercress that’s growing in contaminated water, for example. We really need to do more tests of more species in more diverse growing conditions to understand how general it is.

You write that these plants may play a more important role in our diets when food is more scarce or expensive. Can you explain?

There are certainly historical and contemporary examples of societies in which people replace commercial foods with foraged foods in times of need, whether that’s because of a war, famine, political displacement, and poverty.

edible chickweed in downtown Berkeley, California.

Chickweed in downtown Berkeley, California.

But perhaps more important is the resilience of many of these species and their ability to thrive in environments that are challenging to other plants. As the climate changes, we may need to bring some of these historical foods back into our diet. For farmers to start embracing the use of some of these plants as edible cover crops, to start harvesting them between the rows and at the margins of their farms, to have more biodiversity on farms and in our diets is really going to be important for long-term food security.

If more farmers start selling these plants, will that make them more palatable for the general population, which may be less inclined to walk down their city street with a pair of scissors and start harvesting?

I don’t think we’re going to get many people to forage for themselves until or unless there’s a catastrophe like an earthquake that makes it too hard to get food by other means. And that’s probably not the best time to start learning to forage.

It’s a much easier thing to approach with people who are already gardening or already farming, and say, ‘Hey, you’re actually growing more food than you realize. These other things are delicious, too.’

Common cat's ear

Common cat’s ear.

We’re trying to get across the message to farmers that this is an additional source of income, an additional way to help the biodiversity of the farm, support pollinators, and help the soil in other ways. The way these plants grow can make them more labor intensive to harvest, even though you don’t have to pay for the seed and you don’t have to water them deliberately. I’ve been trying to get farmers to sell a mixed bag—a wild braising mix or a wild salad mix. Just like with mesclun mix, you can do the same thing you know with a broader variety of plants rather than just the ones that are currently in fashion.

Do you have a sense of who is foraging in the areas you studied?

Many immigrants to the U.S. bring with them a culture of foraging and a cultural heritage of eating these plants. In the Bay Area, there are [people from] Southeast Asian cultures, Mediterranean cultures, and Central and South American cultures that do forage.

The areas we studied are deliberately urban, and we didn’t come across anyone else foraging there. People expressed interest in what we were up to; the responses ranged from “that’s gross” to “that’s interesting, tell me how.” And then there’s a whole foodie, somewhat hipster, new food scene of people who are foraging and that’s a very different crowd, a different socioeconomic stature.

All of these things have been known to be food for thousands of years and have probably been part of human diets for tens of thousands of years. The question is, why did they fall out of favor? Why are they not part of regular diet in the global North?

How would you answer those questions?

Ultimately the way to really shift things is to get these foods into the ordinary food supply by harvesting them on farms and having them distributed and delivered to consumers in exactly the same way that as current conventional crops are.

In our culture, we have what amounts to a “food clergy” that tells us what is and isn’t food. They want to bless and sanctify certain plants and not others. You know that it’s been blessed by the food clergy if it’s in a plastic bag at the grocery store, on your plate at a restaurant, for sale at the farmers’ market, or in your CSA box.

Cutting out the middleman and asking people to make that determination of whether something is or isn’t food for themselves is really difficult in our society because we aren’t trained to do it. The best leverage to get these plants normalized and back into our diets is through the [same] food clergy—it’s to get them on the plates at restaurants, into the stalls at farmers’ markets, and into the grocery store.

That’s happened with a few things. For example, you will find chickweed and purslane and nettles at some restaurants. But it’s still not something you see that regularly. The actual sensory experience of eating an unfamiliar plant that has unfamiliar mouthfeel or strong flavor remains a barrier to consumption.

Sweet fennel.

Sweet fennel.

We did start to investigate barriers to consumption through surveys of people at farmers’ markets to try to understand whether they were familiar with some of these wild foods, whether they eat them already, whether they would eat them if they were presented to them on a plate or by someone they trusted. The results were very promising.

I would think that food-focused, sustainability-minded places like Berkeley would be more supportive of foraging, but your report mentioned that there and elsewhere, foraging is largely illegal. Is public policy a barrier?

Basically, in the U.S, you can only forage on your own land; you can’t forage on public land. That’s very different from a lot of the world, including most of Northern Europe and the Scandinavian countries in particular, where there’s this notion that you can collect a hat full of anything.

I don’t expect urban foraging ever to be huge and so it’s not like our laws are stopping a huge amount of consumption. I co-authored a white paper on why schools and municipalities should allow foraging, especially of non-native invasive species, as a way to have some kind of integrated pest control and feed people at the same time.

This feeds into urban planning and having a productive ecology in an urban environment. We should be thinking about foraging as a component of land management in an urban environment.

Edible weed photos CC-licensed by Philip Stark on iNaturalist.

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  1. Wednesday, September 26th, 2018
    Thank you! For doing the work and for this thoughtful article. I like that it acknowledges issues such as soil contamination and cultural attitudes toward foraging and unfamiliar foods. It is nice to read an article that is hopeful and intriguing rather than evangelical :-)
    In particular, I was pleased that - at least in this case - toxins weren't a problem.
  2. Thursday, September 27th, 2018
    Very interesting article! Thank you for the information! I had no idea that it was largely illegal to forage on public property. Seems that we need to change some of the laws to keep up with the times, especially if the 'hat full' notion were incorporated. Again, thank you for the very useful article.
  3. Linda f La Chance
    Thursday, September 27th, 2018
    Thanks for the information. do you provide a guide to identify these plants?