Last month, I placed some seedlings that I had started about 15 days earlier in cups and planted them in my 32 square-foot water garden. The experiment suffered from a number of problems. First, the hydrocorn supporting the seedlings didn’t hold the seedlings securely enough to develop much of a root system.
When the seedlings were placed in the water tray, they began to suffer. The first symptom was drooping leaves. That is an indication that roots are suffering from oxygen starvation. The tray was outfitted with an oxygen generation system using hydrolysis, but it wasn’t generating enough oxygen for the plants.
I replaced it with six lines of irrigation tubing with holes 6” apart. This is attached to an air pump with an output of about 350 gallons of air per hour. This system solved the problem.
Next, I noticed that the plants were suffering from both a magnesium deficiency and a slight calcium deficiency. These deficiencies were caused by a lack of these elements in the tap water. The reason for this is because most fertilizers are formulated for use with “average” water. For example, San Francisco Bay cities use runoff water, which has very little dissolved salts.
Finally, I noticed that my pH meter was not performing correctly and was giving me incorrect readouts, resulting in plants suffering from a solution with a pH below five. This was just corrected a couple of days ago, and the plants are already in recovery.
I have better news regarding the greenhouse garden. The plants there are doing fabulously. I have plants in two different systems drawing water from the same tray. The first uses clay pebbles. The 8” tall colanders are submerged 2” and above water 6”. A pump constantly delivers a gentle stream of water that flows over the pebbles, creating a water/nutrient film. Large air spaces between the pebbles provide the roots with plenty of air. The other group of plants uses a planting mix and is irrigated using a wick system. Nylon rope hangs from holes in the bottom of the containers into the tray. Water is drawn up to the container as it’s used by the plant by capillary action, the same way a tissue draws water. In addition, the container receives about eight ounces of water three times daily using a timer to regulate a small submersible pump.
The plants have been doing really well, but are close to the 9’ ceiling. Looking at the situation, I realized the tray was sitting on a table. So I had some friends help me empty the tray of the plants, drain the water, remove the tray from the table and then place it on a Styrofoam board to stop heat transfer with the greenhouse floor, and then reassemble the unit.
Then the tray was put back together. In late July, the plants were light-prepped for a mid-September harvest.
It isn’t too late to plant with seed or clones outdoors or in a greenhouse in areas where it stays warm through the end of October. In other areas, plant in containers that can be moved outdoors on warm days and lit indoors on cool or rainy days. The plants will immediately start to flower as they grow and will be ready to harvest in 60-70 days.