Indoors, hydroponics allows for the maximum use of space with a minimum of the mess and bother associated with dirt gardening. Outdoors, hydroponics permits gardening in areas with poor soil, or no soil at all, such as patios and rooftops. Recirculating systems conserve precious water and expensive fertilizers. Hydroponics is the science of growing plants without soil, most often in a soilless medium. In hydroponics, the inert soilless medium that provides support for the plants' root systems contains no nutrients of its own.
Nutrition is supplied by the nutrient solution, a mixture of pure water and dissolved nutrients.
With most hydroponic systems, the solution passes over the roots or floods around them at regular intervals. Oxygen, essential to the health of roots, is either incorporated in the nutrient solution or drawn into the root area when the system is drained. Even the best soil rarely holds as much oxygen as a soilless hydroponic medium. The oxygen around the roots speeds the plants' uptake of nutrients. Plants grow faster hydroponically because they are able to assimilate nutrients rapidly and completely.