Indoor daily temperature swings

[MCSchrum]

I've read that many orchids need a day-night temperature difference of 10-15F in order to grow and flower properly. I have a thermometer that records daily high and low temps in my orchid room. During the summer, with the air conditioner going, I generally get nightly lows of 72F (which is the temperature set on the thermostat), and the sun coming in the window during the day raises the temp to around 80F. I grow all my plants near an east-facing window and under lights. All of my plants are in the same room on the second story of my apartment. Since I'm currently only getting about an 8 degree F difference in temperature every 24 hours, is there a way to increase this temp range, short of changing the setting on the thermostat daily? My fiance probably wouldn't approve of sweltering days and frigid nights throughout the apartment.

[chemist]

I think you sould be ok
8 is close to 10.
Also remember that when sun shines closer to the window temp will be higher than farther from it so your plant probably getting 10-15 degree difference between day and night.
Meanwhile keep windows open in fall to get lower temp at night and you should be able to make them flower.

[MCSchrum]

That's a good point chemist. I have the thermometer in the shade, underneath the leaves, and farther from the window because I wanted to attempt to measure the ambient temperature of the room. So the plants closer to the window are probably getting a higher temperature during the day, and thus a wider diurnal range of temps.

I also try to keep the windows open in the house during spring and fall, because it gives my orchids the temperature range they need, and it keeps my electric and gas bills low!

I considered shutting the AC vent off in the orchid room to raise the temps during the day, but it seems like that raises nighttime temps as well.

[raybark]

Most plants do well with a diurnal change. However, that is not to be confused with phalaenopsis, which need about two weeks of a 10- to 15-degree drop in AVERAGE growing temperature in order to reliably initiate flower spikes.

[MCSchrum]

Ray, I've got a few Phal hybrids, and I've been able to successfully bloom them every fall. I keep the windows open during most of September and October, and this gives me the temperature change drop they need.

I've read that most orchids benefit from a temperature drop every night, because it allows their metabolism to slow, and this somehow contributes to their overall health. This is the reason I asked about a summer time diurnal temperature swing.

[78Terp]

There was an article in November 2014 'Orchids Magazine' (the monthly AOS publication) that talked all about the benefit orchids get by the lower overnight temperature. The short of it is that when the temp is lowered at night 15-20 degrees F, it allows the orchid to store energy that will be used later for blooming. Not lowering the temp prevents that energy storage and can prevent an orchid from blooming or blooming well.

[MCSchrum]

Terp, thanks for clearing that up. I knew there was some sort of physiological benefit to a temperature drop, but I wasn't sure what the mechanism was. I'm not quite able to get that 15-20 degree swing. Maybe I'll try closing the vents in the morning, and opening them at night. Perhaps that will give me the warm days and cool night my plants crave. If it leads to more and/or bigger blooms, then I think it's worth the trouble.

[78Terp]

I live alone so I can do it for my orchids without complaint from anyone else.