This happened within at most two days

[Roberta]

A note... if some of the others came through OK... depending on parentage, some hybrids and species in the Cattleya group are more cold-tolerant than others. (I cherish the cold-tolerant ones since I do most of my growing outside) Also, very specific location can mean that one plant gets hit and others escape. I had a situation where one plant at the edge of the shade cloth got damaged, the rest, which were fully underneath, were fine. I visualize cold air rolling off the edge of the shade cloth surface and hitting the exposed one. At the freezing point, one degree or less can make the difference between safety and disaster.

[HumbCa]

Originally Posted by SouthPark

Maybe those plants down toward the back - in the background - are Epidendrum Nocturnum.

The plants showing the bruising/black-coloured patches in the large pots in the foreground are definitely cattleya type. Did any of the other types of orchid in the green-house get this same bruising condition?

You're right, I was in such a state of disarray I didn't even pay attention which plants I was taking photos of, I just posted them ASAP and replied without thinking at all or checking the pictures twice, sorry.

Update on the situation: I put the damaged plants somewhere warmer, I also made a small temperature logger with a microcontroller, I'll soon have data on how low the temps have been these days.

Next step is modding the micro to also turn on a heater when needed. Any of you got experience with heaters?

[Ray]

Keep a close watch. Cold damage is easily susceptible to bacterial rot. If you see that happening, cut off the damaged tissue with about a 1cm margin, and using a Q-tip, dap the exposed wounds with cinnamon powder.