Hydroponics is a method by which plants are grown in nutrient enriched water instead of soil. The Aztecs used hydroponics in the 12th century by seeding rafts made from rush and reeds and floating them in nutrient rich lake water. In the 21st century, you can build an inexpensive and easy system known as a lettuce raft. The lettuce raft is an ideal DIY hydroponics project for the inexperienced hydro-gardener. You can grow greens and lettuce, such as Swiss chard, spinach, Romaine lettuce, as well as herbs and small pepper plants in this Do-It-Yourself lettuce raft.
Dark-colored plastic container measuring approximately 18-to-24 inches wide and 9-to-12 inches in width, with a depth of 5-to-6 inches
- Rigid 1-inch Styrofoam, available in large sheets at home improvement stores
- Plastic 1/4 inch tubing, approximately 6 feet in length
- Air stone of the type used in aquariums, available at pet supply stores, to oxygenate the water
- Air pump to power the air stone
- Hydroponic nutrients: These are soluble nutrients and are available at hydroponic supply outlets or online
- Net pots, clay pellets, rockwool cubes and seeds
Use an electric knife to cut a rectangle of Styrofoam measuring 1/2 inch less in both width and length than those of your container. This is your raft.
Use a net pot as a template for cutting holes in the raft. Place the top of a net pot on the raft at the top corner, leaving a 1-to-2 inches gap from the edges. Trace the net pot onto the surface; repeat this step, creating rows across the raft with approximately 4 inches between each circle.
Clean the container with a mild bleach solution. Rinse thoroughly and dry. Place the container on a table near an electrical outlet.
Putting It Together
Place the air stone into the container and connect it with the tubing to the air pump. Place the air pump on the table; do not put the air pump in the container.
Mix the nutrient solution according to the manufacturer's instructions. Mix enough to fill your container just over two-thirds full and add the solution to the container.
Plug in the pump to test the air stone. The water should bubble and ripple along the surface.
Place the raft onto the surface of the nutrient enriched water. The raft should float and there should be a slight gap between the raft's edges and the container.
Add clay pellets and one rockwool cube for each number of net pots needed for your raft. For each net pot: Fill halfway with clay pellets and place a rockwool cube in the center. Fill the remaining space with pellets. Place three seeds of the lettuce, greens or herb of your choice into the center of the rockwool cube. Place the net pots into the raft.
Keep the water level high enough in the container so the portions of the net pots beneath the raft are immersed. This keeps the rockwool cube -and the germinating seeds- moist and well-fed.
Use a hole saw to cut the holes in the raft if you have one. An electric knife or utility knife will also work.
Renew the nutrient solution in the lettuce raft every three weeks to avoid nutrient depletion.
Check the pH levels with a pH tester. The pH should be between 5.5 and 6.5 for optimum growth and plant production.
Avoid root rot by using the right size air stone and air pump. Stones and pumps that are too small do not provide enough oxygen.
For this DIY hydroponics project, you can also use seedlings germinated in a seed starter tray then transfer them to net pots for the lettuce raft. Grow small plants such as herbs and ornamental peppers as well as greens and lettuce.
Reference and Credits
Urban Garden Magazine: https://urbangardenmagazine.com/2009/12/salad-365-how-to-build-your-own-hydroponiclettuce-raft-system/
Photo Copyrights: Shelly McRae