Hydroponic gardening is the science of growing plants in a controlled environment without soil - free from soil borne pests and diseases. Hydroponically grown plants are raised in greenhouses under carefully monitored and controlled conditions. Gravel is normally used as the medium to support the plant's roots within the hydroponics greenhouse. Carefully mixed nutrients are then periodically fed to the crops in liquid form - a method called sub-irrigation culture. Once seedlings are planted almost all of this work is done by automation. In these hydroponic greenhouses sensors within the gravel are used to determine when the plants need more nutrition and turn on the pumps, giving the plants the just the right amount of solution.

These hydroponically grown plants are fed the exact nutrients needed for rapid growth and volume production. Some hydroponic gardeners use special tanks that are made from big drums which are cut in half. The bottom of each half is brazed with brass tubing. A hose hose is clamped to one end of the tube. The other end is attached to a similar tube which is brazed into a small can.

Inside the tanks the can is painted with an asphalt based paint in order to prevent metal surfaces from rusting. The tanks are filled with small sized gravel pellets.

The hydroponic gardening process starts with 'planting the tanks' by first starting seedlings in carefully prepared paper cups full of vermiculate to allow the hydroponic solution to enter. After the plants are started, the entire cup should be placed in the gravel. The plant's roots are irrigated from below as the fluid flows down the hose and into the gravel. The system is set up to ensure that the crops are moist but are never flooded with solution for more than a few seconds.

The advantages of hydroponic gardening in a greenhouse are numerous. When crops are grown hydroponically, crop yields are increased dramatically over conventional agriculture. For example acre of land will yield five to the tons of tomatoes. The same amount of space will yield 60 to 300 tons when grown hydroponically. A lettuce crop grown in a hydroponic greenhouse will yield an increase of 12,000 pounds over conventionally grown lettuce.

Hydroponic gardening provides other advantages besides increased crop yield. The hydroponic greenhouse environment extends the growing season and doesn't require heavy labor. And of course the obvious -there's no need for greenhouse soil!