how cold is too cold?
 

Hi all
We have been having some crazy northern Ontario weather. I have 2 phals and 2 cymbidiums outside we went from yesterday being 25C to 6C today. I am trying to encourage spikes on these plants so don't want to bring them in prematurely and mess up that process. But I also don't want to damage them or slow them too much (one phal might not be ready to bloom again same with the cyms as I bought them out of bloom this summer at home depot so I have no idea what sort of schedule they are on) So to bring in or not to bring in? is it detrimental to bring them in and out as the weather changes? This is the first year I've put any orchids outside.

I think the Phals should not be out in +6 but my Cyms were out in around +3. I have brought them in now since it seems fall has arrived here. Cym's can take close to freezing but Phals would need a chill of around 55F or 60. Not sure what that is in Celsius, maybe 10 or 12C.

*walks out and grabs phals* One i think has the beginning of a spike I wish I hadn't noticed it so early it might be stalled...its set near a draft still but inside. I see some sort of growth on my cym but i think its just new growth to small to tell yet.

No cool growing orchids like to go lower than 45F if at all possible. Cyms will tolerate 32F for no longer than 8 hours but some damage may be done to the spikes/flowers.

For warm growers like Phals, you are safest in never letting them get below 50F. Serious damage will be done at 40F or lower for any length of time.

I doubt you did any damage to Phals at a short term exposure to 6C (~43F), but don't make a habit of it. If they were at ground level or next to a building they probably didn't even get quite that cold.

As other have said, the Cyms should have no problem with 6C.

they were on my balcony under a large potted raspberry and the cyms... they don't seem to have suffered but ill not let them out unless it warms up a bit again. there back in there inside locations for now.. the cyms ill leave unless it gets colder/windy

I would agree that with warm growers, bringing them in when it gets below 10 C (50 F) is safest. My experience is that my plants, including Phals, have unintentionally experienced temperatures that dipped to 4 C (about 39 F) during the coldest part of the morning, outdoors and unprotected. I would not advise doing this, though.

I think if you have had an average temperature drop of 5 C over the past month or two, you probably have had all the temperature change you need for your Phals.

The easy way to convert. Farenheit to C. Minus 30 and halve the resut.

50F > 20, halve it >10C

Are Catts, Phals, Dens, Vandas and oncidiums the same, more or less? Down to 50F is OK? Or is 55 right? I know they need to go cold enough....

Cymbidiums to 5C yeah?

Fwiw some of my noid Phals saw night time temps in the mid to upper 40s several times last winter, and one morning air temp was a recorded 42F in the room they were in. There was actually frost on the inside of the windows. They didn't miss a beat.

If it is just one night, for a few hours, even warm growers are usually okay, if there is no wind, in the forties. Usually. I do have some plants and orchids that just would not be able to take those temperatures. The noID phals are pretty tough, though, and I usually do not worry about them when temperatures are temporary.
If it is autumn and we begin getting cooler temperatures, I bring my plants inside. It is just not worth stressing the plants just before winter when the conditions won't be completely ideal.