Blackened brasso cattleya leaves?

[SilverShaded]

I think the usual reply to this is often cited as being a fungus, but..

Recently I had several newly imported cattleya related plants start to turn black (and also a doritis!). The doritis was moved to a warm windowsill and given plenty of water and is now ok, but dropped a few leaves on arrival.

The cattleya types were put in a greenhouse at min 12 and moderate humidity. Some that started to turn black were moved to a warmer and more humid section and seem to be ok after dropping some leaves.

Now I would have thought min 12C was fine for most basso-cattleyas so I'm wondering if the blackened leaves were a response to becoming dehydrated. The solution seems simple enough, just move them into the slightly warmer and definitely more humid section, this works, but is it the temperature or the dehydration (or both) which is the likely culprit?

This will help me re-arrange the greenhouse for next winter if i know what the exact problem is.

[euplusia]

A winter minimum of 16°C would do it, however 18°C are better. Our winter nights are long.
In October I made an experiment with 4 virused well established Brassocattleyas. I put the pots outside for 3 weeks. Nights were mostly 2-3°C, and many times the pots were wet from pouring rain. To my surprise the plants did not suffer at all. Not the slightest damage. So I put them in again.

[SilverShaded]

Originally Posted by euplusia

A winter minimum of 16°C would do it, however 18°C are better. Our winter nights are long.
In October I made an experiment with 4 virused well established Brassocattleyas. I put the pots outside for 3 weeks. Nights were mostly 2-3°C, and many times the pots were wet from pouring rain. To my surprise the plants did not suffer at all. Not the slightest damage. So I put them in again.

Not sure what to make of that. They are ok at 2C but 18C is better?