What is Semi Hydroponics?

Semi-Hydroponics, also formally referred as passive hydroponics or passive sub-irrigation, is a unique and simple plant culture technique that allows you to minimize and in some way automate your watering. Semi-hydroponics is a method of growing plants without soil, peat moss, nor bark. What is used instead is an inert porous medium such as LECA, coco and perlite that, through capillary action, transports water and nutrients to the roots. Capillary Action - is the ability of a liquid to flow in narrow spaces through porous medium in spite of other forces, such as gravity.

  • "Capillary action is a property seen in some liquids. It is most pronounced in water because of water's unique properties and because water is the basis of most liquids that we use every day. When you use a paper towel to mop up a spilled drink or use a towel to dry yourself after a shower, you are using capillary action. When you put cut flowers in a vase of water, capillary action keeps them fresh."

~ Ellis, M E, Capillary Action of Water: Definition & Examples, study.com, viewed on 23 June 2019, <https://study.com/academy/lesson/capillary-action-of-water-definition-examples-lesson.html#lesson> LECA (lightweight expanded clay aggregate) Source: Anton Starikov / Dreamstime.com

  • LECA (lightweight expanded clay aggregate) Expanded clay pebbles resemble oddly shaped, semi-rounded pieces of clay-colored popcorn. The high-heat popping during the manufacturing process gives the medium its large, airy macro-pores (spaces between each piece of expanded clay), in addition to its micro-pores, which are contained within each piece of expanded clay. The medium provides plants with hefty amounts of oxygen for fast-growing roots, and it holds enough moisture within its micro-pores to allow for healthy water and nutrient retention from the roots all the way to the top nodes. This spacing also allows for excellent drainage when using top drip or ebb and flow growing methods while still allowing roots to draw water out of the clay’s pores.

Water and fertilizer are held in a reservoir and conducted to the roots as necessary, reducing labor and providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water or on a capillary mat saturated with nutrient solution. Since routine maintenance is much simplified, passive hydroponics can reduce the labor required to maintain a large collection of plants.

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