If you have overwatered an orchid, you can take steps to save it. If the orchid still has some healthy, firm roots, you can salvage it by cutting off all the soft, mushy roots with a sterile tool, like a single-edged razor, and repotting the orchid in new potting material. Go light on the watering for a few weeks to encourage new root development. Using a spray bottle, mist the orchids a few times a day to prevent the leaves from drying out.
If the roots are almost all gone, take these emergency measures but know that recovery is not assured:
Cut off all the dead or damaged roots.
Drench the roots with a liquid rooting hormone like Dip 'n Grow.
Let this liquid hormone dry on the roots for about an hour, then repot the orchid in fresh potting material that has been predampened.
Don't water for a day.
Water once, and then put the potted orchid in an enclosed terrarium.
You can use a high-top propagator (a clear plastic box with vents at the top and a tray below to hold potting material) or an empty aquarium with damp sphagnum moss or pebbles on the bottom to add humidity.
Close the top of the terrarium and put it in a location with diffused light.
In a greenhouse, this would be a shady spot with no direct sunlight. Under florescent lights, put the terrarium at the ends of the tubes where there is less illumination. If the terrarium is in the cool part of the greenhouse or growing area, put the entire terrarium on water-resistant soil or seedling heating mats, available at most garden centers. Get one that has a built-in thermostat set for about 70 degrees F (21 degrees C) to provide bottom heat to stimulate rooting.
If you're concerned about disease, spray the orchid leaves with a disinfectant solution.
A good disinfectant is Physan, a commonly used hospital disinfectant available from mail-order orchid-supply companies or at garden centers.
In this environment of 100 percent humidity, the leaves won't dehydrate, so there will be no stress on the orchid while it reroots. Water the potting material only when it gets dry, keep the gravel or moss in the bottom of the terrarium damp, and leave the orchid enclosed until new root growth is very apparent. This may take a few months.
