How to disinfect granular potting medium? A full breakdown of methods and steps

Orchids' potting medium is also a breeding ground and protective cover fororchidpathogens. For example, southern blight and brown rot are caused by infected potting medium. This disease is the most vicious of all, and to this day there is still no truly effective drug to defeat it; the only approach is prevention first, avoiding infection and outbreak. Therefore, disinfecting the potting medium is a very important part of growingorchidswell. When I first startedgrowing orchids, I suffered the heavy lesson of losing them all. Even today I still feel the lingering fear and proceed step by step with caution. Nowadays, when starting out inorchid growing, granular potting medium is widely used; it has the advantages of being clean, airy and free-draining, which is unfavorable to pathogens, but it is not foolproof either. In fact, after granular potting medium has been used for a long time, it will likewise produce bacteria and viruses that harm the orchid plants. I use granular potting medium for all myorchid growing, and moreover do it in such an excellent environment as a closed balcony. By rights, that should be the best possible, yet brown rot still occurred. The reason was still that the potting medium replaced during repotting was reused without disinfection. Potting medium disinfection generally includes steam disinfection, sunlight disinfection and chemical disinfection. Steam disinfection works well but is very troublesome, and people often give it up because of the hassle; sunlight and chemical disinfection are more convenient but not thorough, and it is hard to avoid pathogens surviving. Nowadays I use the steam disinfection method with sunlight as the heat energy, which is both convenient and reliable. The specific operation is as follows: put the granular potting medium removed during repotting into a large plastic bag, and wait until the scorching days of summer to carry out disinfection. First spray water into the plastic bag to moisten the potting medium, tie the bag tightly (so it does not leak air), and place it on a concrete surface under the sun to bake. The moisture inside the bag evaporates into steam when heated, and the temperature is very high; two or three hours is enough to kill all the pathogens in the potting medium. Fellow orchid growers might as well give it a try. Author: Lao Tie, Zhejiang