At our last meeting, we had discussed the best approaches to deal with the cold weather, what to do before a cold front gets here and how to treat the plants afterwards. 

Ideally, plants should be watered and allowed to dry before the cold front gets here. If time allows, a good application of fungicide such as Cleary's and Dithane should be performed. For those of us who have greenhouses, it is best to cover it with plastic and prevent the cold from coming in. If temperatures fall too low, a heater can be placed in the greenhouse in order to maintain a certain temperature. If that is not available, turning the water on will keep plants warm. Once the water has been turned on, it is very important to keep the water running until the temperature goes back to at least 50F or higher. I would prefer 55F under those circumstances. The watering system will work just the same for those who don't have a greenhouse but can keep orchids watered the whole night without interruption.

Plants that are on trees or on benches should be covered with sheets or light blankets to protect them. Frost blankets are available from wholesalers and are specifically made for plants. They are very durable and can be reused many times. They are lightweight so that they do not damage plants when they get covered. Plastic should NEVER be applied directly onto plants or they will burn. Plants that are under a heavier canopy of trees will be more protected than the ones out in the open. If fungicide was not applied prior to the cold snap, it is important to do it afterwards. The plants were subjected to a lot of stress and cell damage most likely occurred if the temperature dropped a lot ( usually below 40F for most orchids. Some are more sensitive than others.) If rot is being observed on the plants, I usually mix Subdue (10 drops/gallon) with Cleary's (2 tsp/gallon) and Dithane (1 to 2 tbsp/gallon) and drench the plants, roots and all, with this mixture. This past cold front was a real test and I am still amazed at how well some of the orchids have done. 

I add epsom salts (magnesium sulfate) to my fertilizer every time the plants get fertilized. I do believe it makes them stronger and perhaps will tolerate lower temperatures without too much ill effects. I add the magnesium sulfate at the rate of 1 tsp/gallon. 

I hope this little information will be beneficial but I also hope that none of it will be put to the test again this year!

 

Happy orchid growing!