Phrag minutes minimum temperature?

[gonewild]

I like to hear about the minimum temperature Phrags can withstand before tissue damage occurs.
Anyone have firsthand knowledge?

 

[mrhappyrotter]

I don't want to generalize too much based on limited anecdotal experience and no precise measurements, so please don't take this as a scientifically rigorous statement. But your question is quite timely for me, given that I decided to start testing Phrag cold hardiness this year.

My experience has been that Phrags and Miltonias (true Miltonias) are surprisingly cold tolerant, at least for brief periods of time overnight.

I don't know how far and how long you can push it, but I've had accidents in the past where some of my Phrags have experienced temperatures near freezing (even light frost) for brief periods of time, and shown little or no damage. These included things like Phrag. Grande and some others that I can't recall off hand.

Currently I'm experimenting with a clump of Phrag. pearcei, and it's doing just fine in a minimally heated greenhouse where night temps have already dipped as low as 36F/2C so far. Other than dropping some older leaves, which its indoor siblings that haven't had cold exposure are also doing, the plant looks perfectly fine.

Several years ago, I had some extra Miltonia divisions that I was parting with. I placed them next to the foundation of my house in the fall. They got slightly covered by leaves, so I mostly forgot about them. They nearly survived the entire winter (zone 7b) until around February when we had a few nights of lows around 7F/-14C. I may eventually get brave and do a similar test with a Phrag or two.

 

[gonewild]

I don't want to generalize too much based on limited anecdotal experience and no precise measurements, so please don't take this as a scientifically rigorous statement. But your question is quite timely for me, given that I decided to start testing Phrag cold hardiness this year.

My experience has been that Phrags and Miltonias (true Miltonias) are surprisingly cold tolerant, at least for brief periods of time overnight.

I don't know how far and how long you can push it, but I've had accidents in the past where some of my Phrags have experienced temperatures near freezing (even light frost) for brief periods of time, and shown little or no damage. These included things like Phrag. Grande and some others that I can't recall off hand.

Currently I'm experimenting with a clump of Phrag. pearcei, and it's doing just fine in a minimally heated greenhouse where night temps have already dipped as low as 36F/2C so far. Other than dropping some older leaves, which its indoor siblings that haven't had cold exposure are also doing, the plant looks perfectly fine.

Several years ago, I had some extra Miltonia divisions that I was parting with. I placed them next to the foundation of my house in the fall. They got slightly covered by leaves, so I mostly forgot about them. They nearly survived the entire winter (zone 7b) until around February when we had a few nights of lows around 7F/-14C. I may eventually get brave and do a similar test with a Phrag or two.

That's great information.
Do you have any observation that the Miltonia was undamaged at near 32°F? Were they in a dry or wet situation.
P. pearcei is a lowland species so likely the least cold tolerant Phrag species.

 

[big923cattleya]

This might be relative to your research.
I was a little lackadaisical in bringing in my last few Phrags this Fall. It was mid October, I had left three outside.
Well this particular night, the low recorded by my little weather station said 30F as the overnight low. I brought them inside. They were sitting on the top of a bird bath in a tray.
I am typically 3-4 degrees colder then the weather data on my cellphone. That recorded a night time low of 33F.
But within three hours my Phrags coming in, they looked to be suffering. They died completely. Was is really 33F, 30F or something else.
No ice on the bird bath.
No frost near plants.

 

[gonewild]

This might be relative to your research.
I was a little lackadaisical in bringing in my last few Phrags this Fall. It was mid October, I had left three outside.
Well this particular night, the low recorded by my little weather station said 30F as the overnight low. I brought them inside. They were sitting on the top of a bird bath in a tray.
I am typically 3-4 degrees colder then the weather data on my cellphone. That recorded a night time low of 33F.
But within three hours my Phrags coming in, they looked to be suffering. They died completely. Was is really 33F, 30F or something else.
No ice on the bird bath.
No frost near plants.

 

[gonewild]

How long do you think the plants were exposed to the 33° before you moved them? We're the mature hardened plants or softer seedlings?
Good info to add thanks.

 

[big923cattleya]

Mostly near blooming sized stuff. Either 5” or 6” pots.
It would be nearly impossible for me to say except here in the northern part of the country, you will typically find your lowest overnight temperature to be about 45 minutes to an hour after sunrise. Maybe because even though the sun is technically up, it’s first rays are ineffective until they reach Earths surface.
I have to idea of how to prove this but I have a feeling it might have been 33 for a couple of hours. It was dead calm. And as you know the clear nights produce colder temperatures then a cloudy nights. Those clouds form a blanket keeping some heat from escaping.

It was 27 this morning.
Next weeks nights are forecast to be 26-30 degrees.

 

[gonewild]

Mostly near blooming sized stuff. Either 5” or 6” pots.
It would be nearly impossible for me to say except here in the northern part of the country, you will typically find your lowest overnight temperature to be about 45 minutes to an hour after sunrise. Maybe because even though the sun is technically up, it’s first rays are ineffective until they reach Earths surface.
I have to idea of how to prove this but I have a feeling it might have been 33 for a couple of hours. It was dead calm. And as you know the clear nights produce colder temperatures then a cloudy nights. Those clouds form a blanket keeping some heat from escaping.

It was 27 this morning.
Next weeks nights are forecast to be 26-30 degrees.

As a point of reference that cold night in the bird bath what might the temperature have been at midnight?

 

[big923cattleya]

It had been a fairly nice day. At midnight it was 39 degrees. The weather dude said a low of around 35. It obviously dipped lower then that.

 

[Arne]

Actually, the lowest temperatures occur usually between 3 and 6 in the morning. I am currently having some Dendrobium outside and whether I’m taking them in or not seem to depend entirely on the very early morning temperatures. I’m in Maryland but the same seem to apply to many locations.

 

[big923cattleya]

There is a substantial difference between Delaware weather and Michigan weather.

You our winter weather might be more like our April.

 

[Silverwhisp]

This might be relative to your research.
I was a little lackadaisical in bringing in my last few Phrags this Fall. It was mid October, I had left three outside.
Well this particular night, the low recorded by my little weather station said 30F as the overnight low. I brought them inside. They were sitting on the top of a bird bath in a tray.
I am typically 3-4 degrees colder then the weather data on my cellphone. That recorded a night time low of 33F.
But within three hours my Phrags coming in, they looked to be suffering. They died completely. Was is really 33F, 30F or something else.
No ice on the bird bath.
No frost near plants.

How wet, or dry, were the plants when they were left out all night?

 

[big923cattleya]

Since I was in the midst of bringing things inside, they were fairly dry.

 

[mrhappyrotter]

That's great information.
Do you have any observation that the Miltonia was undamaged at near 32°F? Were they in a dry or wet situation.
P. pearcei is a lowland species so likely the least cold tolerant Phrag species.

In years past, the Phrag. pearcei has stayed out until night temps dipped into the low 40F (4.5C) range with no signs of damage. I've got multiple large divisions of this plant, so I thought I'd risk sacrificing one "for science". We'll see how it goes. In theory, 36F will be the lowest it gets exposed to this year, unless I mess up or unless something catastrophic happens. Both of which are known to happen.

As for the Miltonia, the divisions that I accidentally left out would have stayed somewhat dry, since I'm sure the conditions that protected them from the cold would have also minimized their exposure to moisture. Last year I kept a piece in a shed, which I only heated when outdoor temps dropped into the 20F (-12C ) range, and it was similarly kept dry, except during warm spells. It looked a little ratty afterwards, but didn't experience any rot or any extreme damage.

 

[Arne]

There is a substantial difference between Delaware weather and Michigan weather.

You our winter weather might be more like our April.

That is probably true. Nevertheless, if you judge by the evening temperatures you will be sadly surprised in general as statics show that the coldest temperatures are usually in the morning at most locations. Google it and you will see.

 

[mrhappyrotter]

Well, I have an update to report on this topic:

The night before last, we had 15F (-9C) lows. I have several thermometers in my minimally heated greenhouse, the lowest of which was registering 33F (0.5C) when I got up yesterday morning. The interior walls of the greenhouse were covered with frozen condensation, but none of the standing water in saucers or buckets had any ice, so the freezing temps likely did not reach much past the walls.

Now that it's a couple days since the event, I'm seeing the first signs of cold damage on my Phrag test subjects (i.e. Phrag. pearcei and some random extras I had).

Prior to this, I've had several close calls due to defective thermostats -- with temps registering on the thermometers at around 34F - 36F, a tad lower than my target minimum of 38F (3.3C).

The damage is probably recoverable at this stage, but my plan is to leave the test subjects out all winter so I have a realistic idea of what to expect in terms of cold tolerance and survivability. The Phrags were always a "stretch", but since I had some extra divisions of things I am fine with any potential losses in the name of science!

 

[big923cattleya]

In my opinion, you are placing way to much faith in your thermometer. I don’t think you can rely on 33 being accurate. And even if it was, how can you say in a minimally heated greenhouse, the entire greenhouse is 33 degrees. You are likely to have a few pockets of 34, 35, maybe 36. Conversely you could have areas of 32, 29, even 27. If they were my plants in my greenhouse, I would use 40, 42 degrees as my target.
Plus it has been my experience that bone dry plants can handle the lower temps better then moist ones.
Look at your car. You can find frost on your car windshield after 36 or 37 degrees overnight. Frost doesn’t form at 32 exactly! Frost is also far more common on clear nights as your ambient heat escapes Earth’s lower atmosphere much more quickly. A cloudy night slows that down. The quick loss of heat on a clear night cools the ground level air quickly allowing the frost to form at 36 and not just 32 or 33.
But getting back to your Phrag leaves, I would not be surprised if the cells that make up the leaves start to have trouble at 38, 36, maybe 34 degrees. Those cells can suffer significant damage with temps above 32. The cell walls collapse.
I mean it is not that cut and dry, 33 we are fine, 32 is catastrophic!