Causes of Stem Rot in Phalaenopsis Orchids and How to Fix It
What do Phalaenopsis growers fear most? Many would probably say "stem rot" - a perfectly healthy plant suddenly develops rot in the stem, the leaves start to wilt along with it, and it's too late to save.
"water pipe" - if you always pour water into the leaf center and stem when watering, the water collects there and can't drain out, and if it's also hot with no ventilation, within a few days the stem becomes sticky and turns black. This is rot caused by suffocation. Especially in summer, if you water again before the potting medium has dried, the stem stays soaked in a damp environment for a long time - how could it not rot?
"wound infection." For example, if you accidentally bruise the stem when repotting, or if the scissors aren't sterilized when trimming dead leaves, bacteria and fungi get in through the wound and slowly "eat" the stem until it rots. I made this mistake before - I used unwashed scissors to cut leaves, and less than a week later the stem started to rot. I regretted it terribly.
In addition, using the wrong potting medium can easily cause trouble too. Some growers use garden soil for Phalaenopsis, or use bark or sphagnum moss that hasn't fully decomposed. These media are either not breathable, or they ferment in the pot and release heat, both of which suffocate the stem and let pathogens slip in.
"fast"! The longer you delay, the more thoroughly it rots, and by then even a miracle worker can't save it.
The first step must be to clean it up ruthlessly. First take the Phalaenopsis out of the pot, gently peel away the surrounding medium, and see how far the stem has rotted. If only the surface is a bit brown, use a sterilized knife to scrape away the rotted part until fresh green tissue is exposed. If the rot is deep, or the stem is even soft and mushy, you have to cut off the entire rotted stem - don't feel sorry for it, keeping it will only let the rot continue. After treating the wound, remember to soak it for half an hour in a carbendazim solution (mixed with water at 1:1000
The second step is to replant it in a new environment. The original pot and medium definitely can't be used - the pathogens are all in there! Find a new breathable flowerpot, use bark or sphagnum moss that has been scalded with boiling water as the medium, and when planting, don't bury it too deep - let the treated stem stay slightly exposed to the outside to avoid suffocation. Don't water it during the first week after planting; just put it in a place with bright, indirect light and good ventilation, and let it slowly recover.
Finally, you have to change your watering habits. From now on, don't water directly onto the stem and leaf center; water slowly along the edge of the pot, just enough for the medium to absorb plenty of water. Open the windows often for ventilation, especially after watering, and don't let it stay too humid around the pot. If the ambient humidity isn't enough, you can mist the surrounding area, but don't spray directly on the stem.
Actually, Phalaenopsis stem rot looks scary, but as long as you catch it early and treat it promptly, most can be saved. The key is still to pay more attention in normal times and not let the stem stay in a damp, stuffy environment all the time.