Davis, California, USA
June 9, 2026
Watercress has been on a roll ever since a federal report declared it a superfood in 2014. The global market for this pungent, peppery herb was estimated at $673 million in 2024 and projected to grow to more than $1 billion by 2033, fueled by interest in its nutrition punch, according to researchers at Growth Market Reports. While most watercress is cultivated outdoors, indoor vertical farms are proving more suitable for production due to higher yields, better control over environmental factors and more of the plant’s health-promoting nutrients. Consumers increasingly see it in local grocery stores.
Yufei Qian led the research in controlled environment agriculture as a graduate student in the lab of Gail Taylor, a distinguished professor in the Department of Plant Sciences. This spring, Qian earned her Ph.D. in horticulture and agronomy.
Researchers in the UC Davis Department of Plant Sciences are meeting the growing demand for plants that both offer greater nutrition and are suitable for indoor production.
“Watercress is the most nutrient-dense leaf on the planet,” said Gail Taylor, a distinguished professor emerita in the department. Nine years ago, she started a research collection of plants drawn from botanical conservatories, seed companies and local nurseries.
Pulling from that resource, a team in Taylor’s lab, led by recent Ph.D. graduate Yufei Qian, is experimenting with 32 unique lines of wild watercress collected from 16 locations in nine countries, and they’re growing them under two lighting regimes. They want to develop plants with better nutrition, sensory qualities and yield – and that are well-suited specifically for indoor farming systems.
The team has published a paper in Frontiers of Plant Science that offers guidelines to breeders who are improving leafy greens for soilless, indoor systems. Such systems are called controlled environment agriculture.
“Up to now, there hasn’t been very much information to help breeding programs for controlled environments,” Qian said. That’s because people breeding for CEA have very different goals and challenges compared to those breeding for field production.
“For example, there is limited shelf space in CEA, so crops need to be more compact but still maintain a high yield. Pests, weather and fertilization are better controlled in indoor growth settings, but plants must adapt to the LED lights we use,” Qian explained. “We also have shorter growth cycles in CEA for clean, high quality, year-round production.”
As part of their study, the researchers dug deep into the natural chemicals that give watercress its peppery flavor: glucosinolates. These sulfur-rich compounds also have anti-inflammatory, antioxidant and anti-cancer properties, according to studies.
The scientists discovered new glucosinolate profiles in wild watercress. “This offers excellent potential for developing new varieties of watercress for commercial production,” said Taylor, who oversaw the research.
Variety and blue light make a difference
In the container farm on the UC Davis campus, watercress grows from vertical panels, exposed to a combination of red and blue light. For the experiment, some plants got extra blue light just before harvest. (UC Davis)
On the UC Davis campus, a shipping container converted into a controlled agriculture facility became the proving ground. The researchers grew plants in that indoor farm using two LED light regimes: A combination of red and blue light was the control; the experimental regime also used red and blue, but added extra blue light just before harvest. Blue light at that stage stimulates plants to produce chemicals that boost nutrition and enhance flavor. Qian’s goal was to understand how genetics and light interact to affect plant growth, nutrition and flavor.
Looking at growth characteristics, the scientists found wide differences among the varieties. Traits such as leaf size, stem length and total biomass varied by 68% across the group. Taste-related traits, including sweetness, varied by 45%.
Looking at nutrition, the scientists measured compounds including glucosinolates and vitamins A and C. They also measured carotenoids, which create red, orange and yellow colors and benefit the eyes, skin, brain and cardiovascular system. Traits for nutritional qualities varied by 43% among the plants studied.
“This shows that wild watercress has strong natural diversity that breeders can take advantage of to improve the crop,” Qian said.
When exposed to extra blue light just before harvest, the plants responded differently depending on their genetic background. This means the nutritional profile of watercress is flexible, or “plastic,” and can change under different light conditions, Qian wrote.
Some glucosinolates reacted to extra blue light in opposite ways. Others showed mixed responses, depending on the specific variety of the plant.
Carotenoids -- especially lutein, which is important for eye health -- increased consistently under extra blue light across most varieties. “Overall, they showed an active response to treatment light,” Qian said.
However, vitamin C, glucose and overall antioxidant capacity decreased under extra blue light treatment compared to the control, with strong differences between different lines of watercress, including from plants collected in different areas. (Read the paper for the justifications behind this.)
Using all this information, the researchers identified six promising “donor” varieties with desirable traits.
“Our next steps will be integrating useful traits of interest into a breeding population and dissecting the underlying genetic architecture to improve watercress yield, taste, postharvest shelf life and nutritional profile better,” Qian said.
In the broader picture, this research shows the potential for controlled environment agriculture, Taylor observed.
“Indoor vertical farming provides us with an opportunity to change the paradigm of plant selection and breeding,” Taylor said.
Collaborative approach with international impact
Many people in the Department of Plant Sciences and beyond participated in Qian’s research.
Ella Katz, a UC Davis alumna and postdoctoral researcher, and Dan Kliebenstein, a professor in the department, contributed. In the UC Davis Postharvest Research and Extension Center, Adrian Sbodio and Bárbara Blanco-Ulate trained Qian to measure BRIX in watercress leaves.
As a part of her work, Qian started a training program in controlled environment agriculture that created mentor-mentee relationships with students. It offered hands-on experience ranging from sowing seeds, to propagation, to harvesting in a scientific experiment. The program attracted 14 undergraduate interns from UC Davis, plus a high school summer intern from Woodland, Calif., and a visiting student from ETH Zurich, Switzerland.
They all contributed to this project as part of their experiential learning and are now pursuing careers around the world.
“It’s a very inclusive program,” Qian said. “Students from all majors, all years, domestic and international, are all welcomed here.”
Related links
Read Yufei Qian’s paper here: “Breeding indoor watercress for enhanced crop biofortification: harnessing natural variation of wild germplasm,” published in Frontiers in Plant Science. In addition to Gail Taylor, co-authors include Ella Katz and Dan Kliebenstein.
Support for Qian’s research came from the John B. Orr Endowment.
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