Achieving day/night temperature differential indoors
 

My question is fairly straightforward. I am reading about Paphiopedilum culture and this seems like it will be the most difficult parameter to get right.

Living in SE PA, the warmest 5 months of the year should present generally favorable conditions for keeping many mottled leaf Paph species healthy, so I plan on growing my Paphs on my porch, sitting in a large fishbowl to augment the humidity, while still allowing for some air movement. Of course, when heatwaves occur or days below 65F or so, I can simply bring the plants indoors. But, all in all, the warm days and cool nights should allow species like P. delenatii and P. bellatulum to do well.

From October-April I will have to grow in a viable indoor setup. Ambient indoor temperatures should be between 65-72F but this will not allow for much diurnal temperature variation or for cool (even chilly in some cases, like for P. armeniacum) nights. How do you all maintain such a temperature differential in your indoor growing setups, especially to simulate habitat temperatures in the cooler months? Getting an indoor growing growing tank down to, say, 50F at night seems like a challenge. Do any of you use refrigeration, cold packs, open windows or any other special techniques to keep your Paphs in favorable temperatures?

I might even close off the heat in one room and allow it to stay in the 40s and 50s at night.

In my old house I heated with a woodstove, and grew most of my plants in a room at the far end of the house. By closing the door at night I got a temperature drop of 15°-20° F. Here I grow in a very sunny room in a rather poorly insulated house, so it's really more about temperature rise during the day, but I still manage 10°F or so differential, at least on sunny days.

I grew in a greenhouse in Doylestown for 27 years, before moving to NC about 18 months ago. In the summer, the temperature my plants were exposed to was determined entirely by ambient conditions, and my paphs did extremely well there. You're worrying yourself over nothing.

You're also kidding yourself if you think "a large fishbowl" is going to do anything to augment humidity outdoors. Besides, why would you need to augment it in the first place?

I do nothing special in order to bloom delenatii indoors except that I like my house cold at night in the winter, so the thermostat is set at 58°. I also use a ultrasonic room humidifier whenever I am using the furnace.

Ray,

My understanding is that the Paphs I want to grow require a humidity of roughly 50-60% by day and higher than this (say 60-80%) at night. In an apartment that is heated and air conditioned, humidity that high will be rare at best.

The fishbowl in question is a foot tall with the opening at the top much narrower than the total width of the bowl, so that design will help it retain humidity. That, and I plan to keep live sphagnum at the bottom of the tank (though the orchid's pot will not be sitting in water). Not to mention, the leaves of the Paph should stay at least 6" below the top edge of the bowl, so all in all this should keep humidity quite a bit higher than it would be otherwise.

Thank you for the advice. I think the sensible solution regarding temperature is to devote one room to keeping these orchids happy and adjusting the temperature accordingly. I will let you know how it goes.

You had mentioned growing them on a porch, so I took that to mean outdoors...

Yes, I intend to grow them on the porch during the warmer months, but it is the cooler months I am wondering about. The apartment does not have much a variation in temperature between day and night. Also, it won't get cooler than around 65F, and most of the time 68-72F. I will have to temperature control an entire room to suit my new orchids, which is fine by me.

Does anybody on here have a terrarium/grow tank that has a refrigeration component?

First, let me say that I believe you're being overly concerned about a very minor factor.

Yes, folks have gone to all sorts of tactics for cooling - some have purchased used florists chiller cabinets or wine chillers, and outfitted them with lighting. Others have recirculated water through dorm refrigerators and added a fan and small radiator to the tank, while others have used Peltier coolers.

When your plants are indoors, it would be a lot easier and less expensive to provide a temperature variation by adding a little daytime heat via a heating mat, than to find a way to cool them more at night.

I looked into Peltier coolers on terraria a while back. They wouldn't work well unless you bought a lot of them, and they would have to put the heat somewhere.

You must have been looking at pretty small ones. I have seen solid-state 100-bottle wine coolers...

They typically have two fans - one for drawing air past the cold side of the junction, and another for dispersing the heat on the other side; pretty much the same principle as regular air conditioning.