Temperature control

[dekeesee]

I have a question about elevating heat during the day for my orchids. They are currently on humidity trays in a sunroom that is part of a house with open construction. At this time of year, it is easy to drop temperatures at night, but how do I raise the temp during the day without baking us? On a sunny day it can rise into the 70's but not on cloudy days. Would a heat mat under the humidity trays work? Is it really an issue?

 

[Ray]

A heat mat under the humidity trays will have more effect on raising the humidity than it will warming the plants.

 

[big923cattleya]

You may just have to leave the temperature alone. Just let it change naturally.
The exceptions would be orchids that like it warm or those that prefer it cool.
Take Vandas, in Florida they liked 6 hours of sun on my pool patio. They thrived from 65 degrees to 85, even 90 degrees. This was easy to maintain from October through November and again from Late February through mid May. I had to protect them from too much sun from May through September. I increased air movement and was sometimes forced to water every day. They loved frequent feedings! They liked it warm, NOT hot!!
They often would slow their growth rates through the cooler months. Anything below 55-60 slowed down their growth rate.

Miltoniopsis are kind of just the opposite. They never have grown well for me with daytime highs about 70. Once in a while would be fine, constantly they would suffer. Miltoniopsis preferred nights from 45-55 degrees. I watered those early in the day, used a finer mix and watched the sunshine levels. Too much sun for a Miltoniopsis is not a good idea. They like it bright but not too sunny. But they are “easy to read”. When the leaves are a bright green color, they are happy. When their leaves go Gray-green in color, they are not happy with their growing conditions. They like abundant moisture.
Just let the room temperatures rise and fall naturally. If it stays too cool overall, maybe don’t grow Vandas. But if you want to try a Vanda or two, summer them outside.

 

[dekeesee]

I have primarily paphs and neofinitias with 1 phrag. They seem to be growing well. I may try to put them outside this summer. We are in the shade and on the north face of a hill here so we run about 5 degrees cooler than Philadelphia.