In Aeroponic gardening the plants are watered and nourished by a mist instead of a flow or pool as is the case with standard hydroponic gardening. It is closely related to hydroponics but differs in many major respects. The plant roots and part of the stem are sprayed / misted with nutrient enriched water.
A grow medium is not used, the root systems instead are suspended by a support structure that minimizes contact with the plant. Optimally 100% of the plant should be exposed to the air so as to avoid hinderance of natural plant growth and root expansion and allow for access to pure water and air exchange.
If you have an extensive system and you feel it is economically worthwhile you might also want to invest in CO2 enrichment, such as a C02 generator or Boost bucket. C02 exhale bags are commonly used in greenhouses also, they are an inexpensive route to go and work well for smaller aeroponic / hydroponic scenarios and confined areas.
There are also several do it yourself methods for boosting C02 levels. See: Do it Yourself C02 generators
Mist Droplet Size and Nutrients
As stated at the initiation of this article, Aeroponically grown plants are nurtured by a mist instead of a flow or pool like standard hydroponics. This naturally involves different equipment. Misters, spayers, foggers and similar doohickies create a fine mist of nutrient solution for delivery to the plants roots. A true aeroponics / Fogponics system incorporates deep cycle timers, high pressure pumps and high pressure mist heads to atomize the nutrients into a soft fog / vaporised water to deliver nutrients and oxygen to plant roots.
Aeroponic systems are usually closed systems providing all the water, nutrients and gases needed to provide a sustainable and reliable air culture environment for the robust propagation of plants. A primary aspect of aeroponics in relation to plant root development is the size of the water droplet / the mist. If the mist is too fine the roots tend to develop very fine hairy roots and fail to develop affluent lateral roots which is essential to sustained growth. If the mist / droplets are too large less oxygen is made available to the roots and anerobic conditions sometimes develop. The mist should be in the goldilocks zone, 'just right'. This sometimes involves what some would call excessive tweaking, but once you hit that goldilocks zone it is worthwhile.
Nutrients which are essentially minerals and salt flowing through the equipment tend to accumulate deposits of the these minerals and salts and therefore require periodic maintenance.
Aeroponically grown plants are more sensitive than either soil based or hydroponically grown plants. They require due diligence and constant attention to nutrient density ratios, pH, and assorted factors. Aeroponic gardens are not something advisable for new comers and are best attempted once you have a grasp on the basics of hydroponics at the very least.
Other Types of Hydroponic Systems
Water Culture Flood and Drain Systems Drip Systems
Hydroponic Wick Systems Nutrient Film Technique Aquaponics