To produce food in the face of climate change, we may need to learn from so-called weeds.
Field mustard, or brassica rapa, is a stalky plant with small yellow flowers. Mitten-shaped leaves hug the stalk. But it has fallen the way of the dandelion and the plantain: Once used as a medicinal and edible plant, it is now considered a weed, overgrowing gardens or forgotten lots. While listed as a noxious species in many U.S. states, brassica rapa’s history entwines itself with some of us so deeply it may well be written in our bones.
Bok choy, broccoli rabe, turnip, and brussels sprouts share the same brassica rapa wild relative. They, like almost all produce, have been adjusted by human selection and intervention to be more palatable, appealing, or accessible to consumers. Plants are also manipulated based on the values of the societies they are in. Over generations of growing and eating, the flavors, compounds, and genetics merge into us.
Human manipulations, however, are not always beneficial to the plant, the future generations of people who rely on them, or the ecosystem of which they are a part.
Intensive breeding can lead to a spare genetic base. The Gros Michel banana was the only banana distributed throughout the world in the 1800s. It was loved for its sweet, distinct taste, but the banana’s lack of genetic diversity meant it was quickly eradicated when a fungus called Panama disease wiped out every banana plantation by 1950. This varietal has since been lost to commercial production giving way to the Cavendish banana.
This pattern occurs again and again through history. When Irish farmers planted almost exclusively one species of potatoes, vast swaths of the vegetables died during a potato blight from 1845 to 1852, which pushed many people to emigrate to survive.
So while resilience has been bred out of countless domesticated crops, an abundance of weeds choke farms and take over unnoticed spaces, like a message.
Crops’ Uncertain Future
The threats to plants today are many. Pathogens, or plant diseases, are spreading via new means and into new areas due to globalization and shifting weather patterns. Climate change, too, is palpably impacting crops’ ability to survive in unpredictable weather, elevations of CO2, and the introduction of pests and fungi as a result of rising temperatures. Approximately $27 billion of insurance reimbursement was distributed to farmers for failed crops between 1991 and 2017, according to a study with the Institute of Physics—a number that is projected to go up.
The EPA states that plants become slower at photosynthesizing and more vulnerable to disease when they absorb many of the substances we’re pumping into our atmosphere, including ground-level ozone and pollution caused by chemical solvents. Plants also suffer when they encounter emissions and exhaust, such as smog, that interfere with their ability to absorb sunlight.
Farming practices are due for an update in the face of climate change. So researchers, food activists, scientists, and agronomists are turning their attention to the wisdom of plants that have fallen to the wayside or are growing abundantly without support or intervention—often right beside existing crops.
Feral plants were once cultivated in farm or garden settings. Then, either by manually crossing or naturally mixing with a wild species, their genetics adapted to the region they were in, which made them more resilient than others. As these plants emerge from the furrows and ditches, with their deep wells of genetic diversity intact, their long-ignored presence may offer a solution to strengthen and prepare vulnerable crops for novel climate conditions.
Harnessing Feral Resilience
In the 1400s, colonization spelled genocide for many peoples in the Americas. These disruptions also affected nonhuman species. Plants were brought with settlers—on purpose or on accident—and forced to adapt to new environments to survive. In many cases these plants have come to thrive in their new environments and, in some cases, are spreading like wildfire over the land, outcompeting native plants who have important roles in their ecosystems. One of them, brassica rapa, incorporated itself into the lives of the Pueblo Originario (Indigenous) Rarámuri people.
In the narrow hills and valleys of the Copper Canyon in Chihuahua, Mexico, a field technician of Rarámuri ancestry, Alejandro Nevares, works with the National Commission for the Knowledge and Use of Biodiversity on a plant preservation project with brassica rapa, known in the Tarahumara language as Mekwaseri.
Thanks to hundreds of years of intentional foraging and cultivation by the Rarámuri in the region, Mekwaseri has become more tender and takes a longer time to bolt, or bloom, at which point it becomes bitter and tough. While other crops like corn and mushroom have suffered unpredictable seasons because of climate change in the region, according to Nevares, Mekwaseri continues to grow reliably.
Similarly, rice paddies in Arkansas, where more than 50% of U.S. rice is cultivated, hold a secret that has been more of a burden to farmers than a boon. An invasive species of weedy rice known as “red rice” has crept through the crop, mimicking the early stages of cultivated rice, but then shattering its seed, which stays dormant, sometimes for years at a time. So while this “weed in rice’s clothing” was long viewed as a problem for rice farmers, new initiatives in Arkansas are working to de-domesticate the crop. They are crossing weedy rice with cultivated seed as a way to diversify the crop genetics and create a more adaptive species.
Crops As Stories
Shelby Ellison, assistant professor and researcher for University of Wisconsin–Madison’s Department of Plant and Agroecosystem Sciences, spends her time tromping through Midwestern autumnal fields, hopping over fences, and trekking into ditches in search of a plant that has long been elusive among American crops: hemp. At one point, the Midwest was a hub for fiber hemp, used for making rope and canvas. After the criminalization of cannabis, though, these plants were effectively destroyed.
But Midwesterners still know of ditchweed—the common name for a feral form of hemp—which has persisted throughout the Midwest.
Ditchweed has successfully adapted to its environment and diversified its genome. The plant is now decidedly feral. With all the space, it has grown huge, developing many uniquely long arms and bolstering its seed. These plants are resilient against various pathogens. Having survived many generations on their own, they have adapted to the climates and seasons of the region without human intervention.
“There’s this push right now to develop cultivars that are adapted to the places where we live,” Elison says. She pre-breeds these samples in a range of diverse environments to observe how they adapt in various scenarios in pursuit of outcomes that prove the plant to be resilient, or exhibit features that a prospective grower might be interested in.
With each of the plants characterized, Elison then passes the seeds to Zachary Stansell, who says his “responsibility is to be a hoarder” of germplasm at the USDA Agricultural Research Service’s Plant Genetic Resources Unit. This massive seed bank in Geneva, New York, collects and maintains the plants to be a resource for breeding, education, and research, as well as for cultural preservation.
After the 2018 Farm Bill passed, taking hemp off of the DEA’s schedule of controlled substances, states and tribes began to legalize the production of hemp. In 2021 the USDA mandated that the Agricultural Research Service’s Plant Genetic Resources Unit also start keeping the first official hemp collection in United States history.
“Conserving the genetic diversity of crops is … an intrinsic good in terms of building climate change resilience,” Stansell says. “These crops are our stories.”
“I like the real junky, weedy, weird things that wouldn’t make sense for a farmer to grow,” Stansell says.“I think of them as a reservoir of unique alleles or variants.”
The seeds from old or weedy species hold vast genetic pools and an inherent connection to the past. Scientists are finding that feral species have high resistance to mildews and diseases, which can be bred into the genetics of other species’ seeds to create resistant varieties of plants.
While the research on incorporating feral genetics is still new, researchers and breeders are already ordering feral hemp seed samples through the U.S National Germplasm system for breeding trials.
The Danger of Oversimplification
Some plants have been bred to need more help growing than others. So while working with feral plants can genetically diversify and make plants more resilient, cross-breeding is not an agricultural fix-all.
The Green Revolution was a large-scale gene manipulation project, and an experiment on what it means to separate people entirely from their foodways. The crops pushed across the world starting in the 1960s consisted mostly of wheat and rice, and were intended to feed as many people as possible. However, not only did they require more human intervention and were vulnerable to disease, they were disconnected from the cultures they were meant to serve.
When a plant is too inbred, it may lose important variants within its genome. That weakens it and makes it more vulnerable. Within a genetically diverse species, however, hidden variants may enable it to adapt to changing local conditions or to enhance nutrition. These adaptations could also prove beneficial to other members of the plant’s ecosystem as shared conditions change.
Linda Black Elk is an ethnobotanist and food activist who serves as education director at NĀTIFS, an organization that promotes the Indigenous foodways of unceded Dakota lands in Mni Sota Makoce (Minnesota). She illustrates the consequences of breeding—both good and bad—with a picture of a variety of stinging nettle that has been bred not to sting.
While the species saves humans from mild discomfort, it also eliminates the protection that aphids who shelter in its fibers require for their protection and survival. These aphids are an integral part of their ecosystem, and their disappearance may disrupt the delicate balance.
That’s why, Black Elk says, Indigenous peoples cultivate plants “not just for their personal benefit but for the world around them.” When humans work with plants through genetic modification and selection, it is important to take into account the needs of the plant as well as the larger ecosystem—not just themselves.
The Challenges Ahead
Feral plants are not always easy to work with for growers. They are less predictable, more erratic, not uniform as they manifest in the environment, and may not have as high a yield. Ferality might not be considered agriculturally “productive” as it is currently defined. Yet we are already seeing the limits and risks of the status quo in agriculture today.
Some organizations are using gene-editing methods such as CRISPR to manipulate germplasms so that they are more predictable, perennial, and sustainable within the environment. There remain unanswered questions about how feral plants can operate for farmers on a larger scale. But there is no doubt that these crops are adaptable, nutritious, and genetically diverse. And such resilient crops may precipitate a shift in approaches to agriculture more broadly.
Importantly, there are no hard and fast rules with plants. Not all plants are adapted to be feral. They are unique beings whose resilience should not be taken for granted. Nor should we dismiss them.
“When a single plant is lost, we also lose a whole set of prayers, songs, and protocols for building relationship with that plant,” Black Elk says.
This highlights the intrinsic connection between food sovereignty and food resilience. As long as we eat food we are going to be selecting and morphing plants. And the conditions in which we feed and fuel ourselves will continue to change.
Similarly, the Rarámuri have corrals of sheep and goats, but the true purpose of these spaces is to fertilize the ground for Mekwaseri. In Chihuahua, Nevares teaches his community about storing and preparing the plants and seeds for generations to come.
Rather than looking at a species as having a single, human-centered function, to understand the feral is to see individual plants with the complexity that seeds entire ecosystems. What would our world look like if we, as humans, learn to adapt to plants instead of making plants adapt to us?
