Hydroponic Lettuce is Growing!

Community food projects help ensure communities have access to healthy food that is grown locally and sustainably. The Webster Environmentalist Coalition grows food with the goal of building food security on campus via a community garden behind the Pearson house. However, there exists a void surrounding the summer growing season when outdoor plants don't grow. My goal is to experiment with a low-cost and distributable method of hydroponics to fill that void and further develop food security on campus.

Hydroponics is a soil-less growing technique where crops, usually vegetables, are grown suspended over nutrient-rich water. Plants absorb the majority of the nutrients they need from the nutrient-rich water, with the rest being made from the sun via photosynthesis. Because the plants are not grown in soil, they are generally protected from soil-bourne pests and diseases and can be grown without environmentally-harmful pesticides.¹² In a 2024 suburban sample from China, only 30% of hydroponic crops carried pesticide residue, compared with 84% of crops grown using conventional methods.³

Our method of choice, the Kratky method, is one of the simplest and most-affordable ways of growing hydroponic crops. Named after Dr. Bernard Kratky, this hydroponic technique involves passively growing a crop through its entire lifecycle without the need for pumps or maintenance.⁴ Enough nutrients and water are added to the container to allow the plant to grow undisturbed until harvest.

In the Kratky method, plants are seeded or transplanted into a net-cup above a container of nutrient-rich water. The seeds or seedlings are supported by a porous medium, usually clay pebbles or rock wool, though many options exist. Enough water wicks up the porous medium to provide a moist environment for germination and development before the plant's roots fully extend down into the water. As the plant develops and absorbs the nutrient-rich water, air flows through the porous medium to fill in the gap left by the water. The plant utilizes small air-roots to take in oxygen from this air-gap to sustain cellular respiration in the plant's roots for continuous nutrient uptake. With a large enough container, there exists enough nutrient-rich water to sustain the plant until maturity without having to maintain or refill the container. In fact, watering the plant halfway through could cause it to drown!

Food-safety is a valid concern for any home-grown hydroponics setup. Here, we suspend plants in a food-safe, BPA-free, polypropylene plastic net cup inside of a glass mason jar. Seedlings are started in peat moss, rock wool, or 100% pure cotton balls, and held in place by clay pebbles. The brown paper bag is being used to block out light to limit algae growth, and to maintain a cool water temperature. To manage bacterial growth, a diluted solution of 3% hydrogen peroxide may be used to clean plant roots and the medium. No pesticides will be used in the cultivation of our plants.

The Kratky method was selected for its low-cost, low-tech materials, and low-footprint. This summer, we plan to see how viable growing hydroponic lettuce is on campus using this method. In the future, there is potential to expand and distribute hydroponic growing kits around campus. If you are interested in growing your own leafy greens or herbs, send an email to grahamscanlon@webster.edu. If you have any questions, comments, or concerns, please contact grahamscanlon@webster.edu or Dr. Miller-Struttmann.

If you are interested in helping out with the Webster community garden, please reach out to the Webster Environmentalist Coalition at websterenvironmentalists@gmail.com.