Watering New Guinea montane orchids

So, strange question for the other New Guinea orchids fans out there. I have a refrigerated (55° nights, 75° days) paludarium in which I grow high-altitude New Guinea Dendrobium (D. cuthbertsonii, D. vexillarius, D. parvulum, etc.), Bulbophyllum, and other genera. Humidity is always over 90% with strong air circulation, and I use an Inkbird thermostat to map the daily temperature variations to roughly the same as temperatures in Mt. Hagen, PNG (adjusting for the time difference). I've noticed--looking at hourly weather--that in Mt. Hagen it usually rains in the afternoon and evening. So, my mister runs at 3:45 p.m. and 10:00 p.m. every day. I know this runs contrary to popular wisdom (to generally water in the morning, and only water at night when humidity is low), due to risk of fungal infections. However, I've never had any issues, and it does match what these species experience in the wild. That said, I'm considering experimenting with a more typical morning watering schedule, just to see how it affects them. Any thoughts, especially from anyone else who has grown similar orchids or who grows in a cooler terrarium?

 

Thank you all for the input. Marni, I'm fairly sure I know of whom you speak. I grow a Bulbophyllum species he discovered, and I visited his successor's greenhouse in San Francisco in December 2019 (a really fantastic place, and a great guy!). I've never had issues with fungus aside from the one time the fans and refrigerant system were off overnight. The paludarium is small enough that with twin fans it really has strong air movent, even as it is almost permanently damp. I do wonder whether plants like D. cuthbertsonii might not grow better being more wet at night, as long as they have sufficient air circulation, but I agree that we can only go so far in replicating natural environments. It's worth experimenting, so I think I'll try a test of morning watering for a little while, just to see how my orchids respond.

 

Unfortunately, I had to quit the test after day two. My paludarium has limited circulation with outside air (not fully airtight) because that's necessary for the Peltier cooler system to drop the temperature down to 55° at night (it's essentially a little refrigerator; I built it with double-walled glass and insulation) and because the office I'm in had pretty bad air shared with a welding shop (the paludarium is on my desk). So, there's minimal evaporation, and everything stays close to 100% humidity. When the Mistking runs, it leaves water on the glass for hours, so if I mist in the morning, I can't see my plants all day.

Based on observed plant responses, I will continue for now with the afternoon watering (3:45 p.m.). That does reflect the kind of misty, mossy montane forest environment that something like D. cuthbertsonii might grow in. Many plants are growing very well, and those that haven't really taken off don't seem to have issues with fungal infections. I'm sure that would be an issue if I didn't have strong air circulation. The fact that they're all mounted (except for one terrestrial) probably helps as well. The only drawback I've seen to such high humidity is that moss wants to overgrow everything. Some orchids seem to like having moss over their roots, and some don't.

 

I'm not sure that I'm not causing issues for my plants, but most of them seem to be doing well. Maybe something about the terrarium environment is different from a greenhouse setting (although I can't think what). It does seem like some orchids require adjustment to the high-humidity environment. I have a Bulbophyllum ankylochele I got from Ecuagenera that over several months shed its old leaves and grew new ones. My Dendrobium vexillarius is growing quite well, but perhaps that's because of its numerous aerial roots, which dry more quickly.