The Science of Hydroponic Growing

Hydroponics, taken from two Greek words meaning ‘water’ and ‘work’, is the science of growing plants without soil. That is, the plant has a root mass in an inert medium like peat, but nutrients are delivered via solution rather than soil as in a regular garden.

Hydroponically grown plants are healthier than their garden counterparts, since they never come in contact with disease-ridden soil. They also receive an optimum balance of the nutrients they need, and thus produce fruits and vegetables high in vitamin content.

Of course, some type of medium is necessary for the plant to form roots. They won’t grow in air (or they will, but that is another discipline called aeroponics). Plants in soil will ‘shed’ the soil into the liquid nutrient system. The best horticultural rooting medium developed to date is a sponge, but these are fairly expensive. Second best are growing cubes made from some form of shredded compound, like cocoanut or peat. Or use rockwool, a spun synthetic fiber often found in potted aquarium plants, which also comes in cube form. There is also the old standby, perlite. Any inert medium will do (inert means without soil bacteria) for growing a root mass.

For a passive hydroponics system (in which the water does not move), begin with a plastic container. Make sure it is about 6 inches deep. Choose one with a lid, and cut openings in the lid to support the root mass (which can be suspended in anything from a strawberry basket to an old pair of nylons). If your root structure is supported by a sponge or other relatively integrated medium (like coconut peat) you may not even need a basket.

Make two holes in the sides of the container at opposite ends and toward the bottom. Make the diameter of the holes the same as a 2-foot piece of plastic aquarium hose. Install the plastic hose inside the container and add a water stone (also available from any aquarium supply store). If you prefer, you can add sterile sand or rock to the container to support the water stone. You can even add a diverter and install several water stones. A standard aquarium water pump, about $30, attached to this hose will keep the nutrient aerated and prevent the growth of algae. Place this pump outside the container at the other end of the plastic hosing. The opposite hole will also have a plastic hose and serves only to regulate air pressure. Tape the 6-9 inch piece of hose against the side of the container in an upright position. Seal the plastic tubing at the openings with a good epoxy or watertight glue.

Make your nutrient solution. You can buy the mixture from a garden center, or make your own from organic nutrients. Remember plant pH (general and specific requirements of NPK and trace minerals). Remember when locating your hydroponics garden that the nutrient solution is harmful to humans and pets.

Pour the nutrient solution into the bottom of the plastic container, plug the pump into an outlet, add plants to the holes you’ve already made (making sure the roots and medium do not touch the nutrient solution) and, voila, you have a hydroponics garden. Once you have mastered the essentials, you can graduate to an active hydroponics garden, where the nutrient solution moves around the roots either by gravity or using a water pump. You can even graduate to a series of gardens, all using gravity-fed or pumped nutrient solution.

In hydroponics, there are only a few essential elements to keep in mind. First, the root area must be at or very near 100% humidity. The roots will grow out of the medium and into the nutrient solution, but require absolute humidity in the region between the root mass and the nutrient solution to do so. This means your plastic container can’t have any openings that are not sealed either with growing medium or hosing. In other words, there must be no gaps. Buy a container with a tightly-fitting lid. Don’t improvise.

Second, your plants require precisely mixed nutrient solution. If you are not sure how to mix the elements (nitrogen, phosphorus, potassium, etc.) do buy a prepared mix. They are not that expensive.

Third, air is essential to keep the nutrient solution from turning into algae soup and killing your plants. The plants don’t need it; they are busy converting CO2 from their leaves into oxygen. The pump will be the most expensive part of your project, but is a necessary ingredient. Prices range from $10 to $30 for a ten-gallon aquarium pump.

A fourth essential is light. Without proper light, plants can’t engage in photosynthesis (a plant’s version of eating regular meals). Incandescent bulbs are not adequate for this purpose, nor are florescent bulbs. Choose LEDs, which offer full spectrum light that duplicates natural sunlight. Suspend the LED within two feet of the plants growing in your hydroponics garden, and watch them prosper!