What is Hydroculture and how it works?

Hydroculture is a method of growing plants without the use of soil. Hydroponics is a subset of hydroculture and is a way of growing plants using mineral nutrient solutions, in water.
Passive hydroponics or semi-hydroponics, is a method wherein plants are grown in an inert porous medium that transports water and fertilizer to the roots by capillary action from a reservoir, providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water. The various hydroponic media available, such as expanded clay and coconut husk, contain more air space than more traditional potting mixes, delivering increased oxygen to the roots, which is important for every plant. Additional advantages of passive hydroponics are the reduction of root rot and the additional ambient humidity provided through evaporations.

How can a plant live without soil?
Researchers discovered in the 18th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics. Hydroponics is also a standard technique in biology research and teaching.

What is expanded clay?
The clay pellets are inert, pH neutral and do not contain any nutrient value. Their purpose is to hold the plant upright and by absorbing some water, provide humidity around roots.
The clay is formed into round pellets and fired at 1,200 °C. This causes the clay to expand, like popcorn, and become porous. It is light in weight, and does not compact over time. The shape of an individual pellet can be irregular or uniform depending on brand and manufacturing process. The manufacturers consider expanded clay to be an ecologically sustainable and re-usable growing medium because of its ability to be cleaned and sterilized, typically by washing in solutions of white vinegar, chlorine bleach, or hydrogen peroxide, and rinsing completely. Hydroton (clay balls) are sold in 5-50 litre bags. You will need the 50 litres if you have 10 medium-sized plants.

Nutrient solution
Plant food. Special nutrients are available for hydroculture, these usually come in either powder or liquid form which are added to water to make a solution. Hydroculture nutrients differ from general houseplant fertilizers in that they contain extra trace elements. Some nutrient solutions may not be suitable for indoor houseplant hydroculture. You need to check the label if it is for hydro use. Always follow instructions on the label.
Nutrients are available in many different NPK (N=Nitrogen, P=Phosphorus, K=Potassium) ratios, these are expressed as percentages. By selecting different NPK formulations the growth, flowering or crop of the plant can be controlled to a certain degree. In most cases a "grow" or general type is adequate. Care is required not to allow salt concentrations to become too high, nutrients to become too depleted, or pH to wander far from the desired value. We need to look into some chemistry later as certain plants have special needs and sick ones need be treated by adjusting compounds. It is easier than it sounds!

Advantages of Hydroponics  

• Very hard to overwater, almost foolproof
• Roots need Oxygen just like water; spaces between particles provide air flow
• Absorbent aggregate help creating humidity for plants
• Easy to clean, repot and reuse
• Pests and diseases occur infrequently and are easily treated
• Very trendy, sounds scientific yet can be built of scrap :)

Once you get the hang of it, you will want to grow everything like this. Even vegetables! :)