How to Grow Watercress Hydroponically. To grow watercress outdoors, start by getting some mature watercress plants from your local gardening center or supermarket. To plant this vegetable hydroponically, you can follow these steps. Hydroponic Lettuce and Watercress Production Lettuce and Watercress are both grown in a very similar system; the preferred system is NFT (Nutrient Film Technique). How does it work? Watercress has . Then, find a cool, partially shaded spot in a shallow stream or creek and mix some organic compost into the soil. Create holes in the Styrofoam with a size that fits the size of the rock wool cubes. The NFT system uses sliding gullies inside a structure. In hydroponic systems, the plants require growing temperatures to be around 77-86°F for their rapid growth, making indoor gardens or greenhouses just right for year-round watercress production. Since watercress is an aquatic plant, growing it in a hydroponic system is a good idea. Hydroponically grown watercress is produced in Hawai‘i by the nutrient film technique (NFT) where nutrient solution is kept continuously flowing. The simplest setup requires a 1-gallon, food-grade container with a top, as well as water, hydroponic solution, growing medium (like perlite or rockwool), and a mesh growing pot. Gullies are made using the 100 x 50mm rectangular hydroponic channel with … Prepare a Styrofoam sheet, rock wool cubes, a bin, air stone, air hose, and an air pump. More on that later. also been grown in uncovered tanks (1 ft. deep) of non-circulating hydroponic nutrient solution, in which only about 0.1 percent of the water was required compared to Kratky method watercress for raising watercress in soil-less culture is most used and easiest. Fit one rock wool plug into each hole. Basically, little net pots are suspended over a tank of stagnant hydroponic solution so that only the bottoms of the pots touch it.