After doing some reading, and speaking with some experts at internet sites that sell hydroponics equipment, I settled on a type of ebb and flow system called Multi Flow. Hydroponics is defined as growing plants without soil. In the Multi Flow system, plants are grown in a series of pots filled with Hydroton media (a pebble-sized growing medium made from clay). The plant pots are connected by flexible tubes to a larger control pot. This allows nutrient solution to flow from the control pot to the plant pots and back again. Several times a day, nutrient solution is pumped from a large 55-gallon reservoir into the control pot. The solution then flows by gravity into the pots containing the plants. The plants’ roots are allowed to be soaked for 15 minutes at a time; and then the solution is pumped out again from the control pot to the reservoir. The solution in the plant pots flows back into the control pot as the control pot is evacuated to the reservoir, in order to equalize pressure throughout the system. A timer controls how many such ebb and flow cycles occur daily.
All the nutrient solution in the plant pots and the solution in the control pot must be part of a single body of water, so that the levels of solution in the pots rise and fall together as a single fluid body. Since gravity is used as a means of distributing the nutrient solution to the pots, the platform supporting all the pots and the reservoir must be level, to ensure that all the plant pots have equal levels of solution at all times.
To set up a level platform, I constructed a frame from 2"x4" pressure-treated framing lumber, shown in the accompanying photo.
The frame is 152" long and 42" wide. This was designed to just fit into the greenhouse through the rear window and be able to be set down on the floor while still clearing the heater that is mounted on the rear wall. (There isn’t a clear path into the greenhouse from the front, because the front door is too close to the adjacent tractor shed.) A square recessed area is built into one end of the frame to allow the reservoir and control pot to rest approximately 1" below the level of the platform upon which the plant pots are to be placed. This difference in height is designed to allow the nutrient solution in the plant pots to be completely evacuated, while about an inch of solution remains in the control pot. The control pot cannot be completely evacuated, but we do want the plant pots to be completely evacuated, since we don’t want the lowest portion of the roots to be permanently submerged.
To ensure that the frame would be as level as I could make it, I put down six foundation stones on the dirt floor of the greenhouse. These were 8"-square pavers with very flat surfaces that I purchased at Home Depot. I set them into the ground after carving out spaces in the hardened soil of the greenhouse floor, adjusting the height of the stones so that metal rods stretched from one stone to the other were all on the same level. I then filled in the spaces surrounding each paver with the small pebbles (i.e., pea gravel) that will be used as the greenhouse floor (i.e., the portion not covered by the frame). This was done to stabilize the pavers and discourage later changes in height of the platform due to settling. The second accompanying photo shows the frame placed on top of the pavers.
The remaining step was to cover the frame with a type of 3/4" plywood that is normally used as sub-flooring. I used Thompson’s WaterSeal brand Waterproof PLUS Clear Wood Protector on both sides of the plywood and on the edges, to prevent the plywood from becoming a breeding ground for mildew. I didn’t use this on the pressure-treated 2"x4"s of the frame.
Each of the plant pots measures 9" in diameter, while the control pot is 16" in diameter and the reservoir has a 24" diameter. I purchased a 30-pot system. Using a scale diagram, I figured out that I could just fit the 30 plant pots on the platform. Experience should tell me where there might be overcrowding, in which case I might not use all the plant pots. My plan is to have three rows on the platform. The row in the rear, closest to the side of the greenhouse, would be used for the vines (tomatoes, cucumbers, melons, pole beans, etc.). These will be allowed to grow upwards along a nylon trellis made for the purpose. The middle row would be used for medium sized plants that would not seriously overshadow the vines (sweet peppers, zucchini). The inner row, running down the center of the greenhouse, would be used for the shorter plants (lettuce, strawberries, bush bean). This arrangement would ensure that all the plants in the Multi Flow pots would have some exposure to both natural sunlight and the HID lighting that will be mounted and hung from the middle of the roof.
I also plan to grow some plants on the other side of the greenhouse, the side closer to the sun. These would be short plants, such as bush beans, lettuce, strawberries, radishes, etc. They will be grown conventionally in soil using special containers called the Grow Box by Garden Patch. This system uses soil, but has a built-in reservoir that keeps the plants watered from the bottom, as long as the reservoir is refilled occasionally.
I also need to save water from the dehumidifier for use in reconstituting the hydroponics nutrient mixture. (I understand that this has to be done every two or three weeks.) Rain- water or distilled water is required for use in the hydroponics reservoir in order to be able to control the pH of the nutrient solution. My well-water might be too "hard" to use for the nutrient solution. I don’t want to have to buy distilled water for the hydroponics, so I decided to collect and make use of the condensed water from the dehumidifier. I’ve collected some condensate water from the dehumidifier to make up some of the water needed for the nutrient solution, but it’s not clear if I will be able to collect enough every two or three weeks to replenish the nutrient solution on a continuing basis. It would also be nice if I were able to use the same water source to automatically replenish the reservoirs in the Garden Patch containers, but that also will require some experimentation.
All the nutrient solution in the plant pots and the solution in the control pot must be part of a single body of water, so that the levels of solution in the pots rise and fall together as a single fluid body. Since gravity is used as a means of distributing the nutrient solution to the pots, the platform supporting all the pots and the reservoir must be level, to ensure that all the plant pots have equal levels of solution at all times.
To set up a level platform, I constructed a frame from 2"x4" pressure-treated framing lumber, shown in the accompanying photo.
The frame is 152" long and 42" wide. This was designed to just fit into the greenhouse through the rear window and be able to be set down on the floor while still clearing the heater that is mounted on the rear wall. (There isn’t a clear path into the greenhouse from the front, because the front door is too close to the adjacent tractor shed.) A square recessed area is built into one end of the frame to allow the reservoir and control pot to rest approximately 1" below the level of the platform upon which the plant pots are to be placed. This difference in height is designed to allow the nutrient solution in the plant pots to be completely evacuated, while about an inch of solution remains in the control pot. The control pot cannot be completely evacuated, but we do want the plant pots to be completely evacuated, since we don’t want the lowest portion of the roots to be permanently submerged.To ensure that the frame would be as level as I could make it, I put down six foundation stones on the dirt floor of the greenhouse. These were 8"-square pavers with very flat surfaces that I purchased at Home Depot. I set them into the ground after carving out spaces in the hardened soil of the greenhouse floor, adjusting the height of the stones so that metal rods stretched from one stone to the other were all on the same level. I then filled in the spaces surrounding each paver with the small pebbles (i.e., pea gravel) that will be used as the greenhouse floor (i.e., the portion not covered by the frame). This was done to stabilize the pavers and discourage later changes in height of the platform due to settling. The second accompanying photo shows the frame placed on top of the pavers.
The remaining step was to cover the frame with a type of 3/4" plywood that is normally used as sub-flooring. I used Thompson’s WaterSeal brand Waterproof PLUS Clear Wood Protector on both sides of the plywood and on the edges, to prevent the plywood from becoming a breeding ground for mildew. I didn’t use this on the pressure-treated 2"x4"s of the frame.
Each of the plant pots measures 9" in diameter, while the control pot is 16" in diameter and the reservoir has a 24" diameter. I purchased a 30-pot system. Using a scale diagram, I figured out that I could just fit the 30 plant pots on the platform. Experience should tell me where there might be overcrowding, in which case I might not use all the plant pots. My plan is to have three rows on the platform. The row in the rear, closest to the side of the greenhouse, would be used for the vines (tomatoes, cucumbers, melons, pole beans, etc.). These will be allowed to grow upwards along a nylon trellis made for the purpose. The middle row would be used for medium sized plants that would not seriously overshadow the vines (sweet peppers, zucchini). The inner row, running down the center of the greenhouse, would be used for the shorter plants (lettuce, strawberries, bush bean). This arrangement would ensure that all the plants in the Multi Flow pots would have some exposure to both natural sunlight and the HID lighting that will be mounted and hung from the middle of the roof.
I also plan to grow some plants on the other side of the greenhouse, the side closer to the sun. These would be short plants, such as bush beans, lettuce, strawberries, radishes, etc. They will be grown conventionally in soil using special containers called the Grow Box by Garden Patch. This system uses soil, but has a built-in reservoir that keeps the plants watered from the bottom, as long as the reservoir is refilled occasionally.
I also need to save water from the dehumidifier for use in reconstituting the hydroponics nutrient mixture. (I understand that this has to be done every two or three weeks.) Rain- water or distilled water is required for use in the hydroponics reservoir in order to be able to control the pH of the nutrient solution. My well-water might be too "hard" to use for the nutrient solution. I don’t want to have to buy distilled water for the hydroponics, so I decided to collect and make use of the condensed water from the dehumidifier. I’ve collected some condensate water from the dehumidifier to make up some of the water needed for the nutrient solution, but it’s not clear if I will be able to collect enough every two or three weeks to replenish the nutrient solution on a continuing basis. It would also be nice if I were able to use the same water source to automatically replenish the reservoirs in the Garden Patch containers, but that also will require some experimentation.
