The Abundance of Forageable Urban Greens

Foraging for food may not be the foundation of our nutrition, but Professor Philip Stark thinks the practice might provide a better way for us to interact with our cities and ecosystems.

March 22, 2023
By Sarah Siegel, BFI Communications Assistant

Within just a few blocks in Berkeley, you might find the juicy leaves of miner’s lettuce, chickweed, mustards, dandelion, broadleaf plantain, poppy greens, or sow thistle. Bay leaves grow in abundance on California bay trees, and, if you know where to look, you can still find mints, yarrow, sage, and mugwort from last season. Most people in the East Bay see many of these plants as ornaments, or even weeds. But a forager like Philip Stark, a professor of statistics at UC Berkeley, incorporates some of these greens into almost every meal.

“I like how foraging gives me some direct control over my food supply, connects me to nature, keeps me aware of the passage of the seasons,” Stark wrote in an email.

Such a fruitious harvest begs the question: Can urban greens actually provide discernible nutrition benefits? And are urban greens grown in urban, industrialized areas even safe to eat?  

Stark, a BFI affiliated faculty and founder of the Berkeley Open Source Food, says yes to both.

In 2017, Stark co-authored a BFI Policy Brief with Sabine Dabady, at that time a lecturer at the UC Berkeley School of Public Health. The brief, called “Urban Foraging in Municipal Parks and Public Schools: Opportunities for Policymakers,” argued for policymakers to create avenues for citydwellers to safely and freely harvest for some of these plants. Sometimes, the policy brief states, wild foods can be more nutritionally dense — and more affordable — than counterparts found in grocery stores. For example, foraged dandelion can contain twice as much calcium, fiber, and iron as store-bought dandelion greens. 

But are these foods safe? A 2019 study published in PLOS One led by Stark and a list of other BFI affiliated faculty, including Daphne Miller, Thomas J. Carlson, and Kristen Rasmussen de Vasquez, aimed to find an answer. 

The research team utilized iNaturalist, a citizen science project that allows users to upload photos, locations, and species ID from observations, to map and quantify edible greens in the area. A team of faculty and students recorded greens that were deemed visible and available: “Visible” servings were those available to a person with legal access to the property, while “available” servings were those within an arm’s reach of a public right-of-way, such as a sidewalk or road.  

The team of researchers then collected soil samples at 28 sites in Richmond and West Oakland for metal assays, to measure for zinc, copper, arsenic, selenium, lead, nickel, chromium, cadmium, and molybdenum. Edible plant tissue samples were collected from sites where soil testing had shown the concentration of metals to be highest. These samples were lightly rinsed in tap water as if to make a salad, and then dried and submitted for a metal assay. Despite the elevated levels of toxic metal in the soil, the research team found that the plant tissue samples did not contain toxic metal levels that exceeded the US EPA maximum acceptable daily dose. Only one species of wild lettuce, the intensely bitter L. ludoviciana, contained elevated levels of cadmium. The researchers also tested the nutritional content of the foraged greens, finding it to compare very favorably to commercially farmed produce, confirming the safety, availability, and nutritional benefits of urban greens.

While in theory, wild urban greens might be able to provide discernible nutrition benefits for city residents, several logistical and cultural hurdles exist. First, as discussed in the 2017 policy brief and 2019 study, foraging is technically prohibited on most public lands in the US, including in city and regional parks in and around Berkeley. One of the recommendations listed in the 2017 policy brief urged city and state policymakers to develop pilot projects to explore the possibility of safely and sustainably forage foods on public lands.

Secondly, in order for foraging to become a more broadly adopted practice, residents must increase their literacy of edible leafy greens. For example, even if someone walks by a patch of edible greens everyday, it won’t do them any good unless they know how to harvest and prepare them. This is a problem that Stark is actively working to solve — he is the faculty sponsor of the Wild and Fermented Foods decal, a course that introduces students to the under-discovered foods of nature. Berkeley Open Source Food has also published Bay Area Baker’s Dozen Wild Edibles, a guide explaining many of the foragable plant varieties common in the area.With more foragers in the area, it might become necessary to develop an etiquette for foraging to ensure sustainability and prevent over-harvesting.

“If the target is nonnative invasive species, I don’t think we need to worry excessively about sustainability: it’s pretty hard to eradicate, say, dandelion, Mediterranean short pod mustard, or English plantain by picking it,” wrote Stark. “It would take an army of foragers.” 

But for native species that might be threatened by invasive species, some guiding practices might be necessary — potentially modeled after traditional ecological knowledge and principles of the Honorable Harvest, a tenant of traditional ecological knowledge often communicated by Indigenous author and scientist Robin Wall Kimmerer. According to the principles of the Honorable Harvest, as Kimmerer explains in many of her writings and lectures,  one must ask permission from the plant before harvesting, and refrain from taking the first or the last of the season. One should only take what is needed, share readily with others, and use everything that is taken. These practices could be borrowed and utilized by those who forage in Berkeley or elsewhere.

“Foraging makes people more sensitive to ecological issues: if you want to be able to harvest there again next week or next year, you worry about how much you can take, or whether to take the flowers/roots or just the leaves,” explained Stark. 

While even avid foragers including Stark don’t foresee a future in which foraging is a foundation of our nutrition, it might provide a better way for us to interact with our cities and ecosystems. At the very least, urban foraging can help us see our environment as more than just a backdrop to our lives, and see some of these plants as more than just “weeds.”.

“Walking around town feels like walking through a farmers’ market instead of walking through a landscape,” Stark wrote. “It feels very ‘human’ to be connected to the world this way: It’s what our brains are wired for.”