It's the term coined by Ray (firstrays.com- somebody else already linked a page on his site). Basically not true hydroponics because there is not a continual feed of water, but it's based on having a reservoir in the bottom of the pot that is kept fresh by flushing the pot regularly. Usually this tactic goes with having inorganic media like leca, rockwool, rocks, or a mixture. The idea is that once plants are established, you can leave the water loving ones a bit longer between waterings (I think).And what is semi-hydro?
In such a setup, there are two, competing processes, wicking and evaporation. If wicking rate is greater than evaporation, the "rocks" stay moist all the way to the top, which is the ideal situation. As evaporation occurs primarily from the top, as its rate increases, the top "layers" lose all their surface water and appear dry. The greater the evaporation rate compared to the wicking rate, the deeper the apparent "dry line" is within the pot.Does the presence of the above water side holes affect the moisture wicking upward through the leca?
Although I'm not depending on wicking to provide water to the roots I'm curious if the side holes do more than just provide a water reservoir. Focusing on water movement and not the added benefit of airflow through the substrate.