definition of a "freeze"

[Tropicdoc]

After our recent arctic vortex event, I have redefined my definition of a "freeze." To me now, a freeze is when a shallow pan of water will become ice if left out overnight. So, during our recent event, 5 gallon buckets of water holding down the flaps of my greenhouse ended up with ice in them! Now.... that's a freez!. That's not the same thing as air temps dipping down to 31 for a few hours, which had happened a few timers already and caused minimal problems. I believe if you define freeze as weather that will freeze a bucket of water, it changes the list of palms that can handle a "freeze." Just saying.

[Xhoniwaters1]

true that...its all about the plants resistance to cell damage. I have a Serenoa repens seedling growing in a water bottle that I left out. Frozen solid...harder than a brick. 2 days later resumes life like nothing happened. Really a cool thing to observe despite the carnage going on in other parts of my yard.

[Xhoniwaters1]

What's the difference from a plant being say zone 5 hardy and one being no lower than zone 6 hardy. If something freezes solid and stays that way for a long time, frozen is frozen right?-whether it be 20 degrees or -15 degrees. Zoning wouldn't really matter anymore when your talking about what you can and can't plant.

[Xerarch]

I always considered temps of 28-32 a frost or light frost, when temps get down around 25 or 26 or lower, I consider it a freeze. You here this idea around a lot, for example, 26 is a critical threshold for a lot of citrus, you always start hearing about a "freeze" below that.

[displaced_floridian]

I believe the chemical makeup of the plant cells determine how hardy

A plant is. Just as water with salt freezes at a lower temp than pure water,

Plant cells have differing amounts of sugars and electrolytes in

Their 'sap' or juice, so they freeze at different temperatures.

[Tropicdoc]

I like that thought about freezing point lowering of solutions must be how tissue of cold hardy plants survives a freeze or maybe it's the makeup of the cell walls?

[sonoranfans]

A freeze is defined by a phase change, and that happens when pure water hits 32 degrees. A deep freeze is quite a bit colder, but we aren't the first people that have thought about the definition of a freeze. And yes, plant sap freezes a bit lower likely due to freezing point depression. But when that sap freezes it expands and it can cut the plant cell material, this is very bad. Some plants may have more flexible cell material and some have more freezing point depression function in the sap. But there is also the insulation of the growing point and dead leaf bases and fibers can help there. The most important temperature is the temperature of the plant material itself, not the air, and ultimately the growing point in particular. Frost doesn't necessarily happen at 28-32, I have had frost free freezes of 21F in the Arizona desert.

[Tropicdoc]

Some people try to increase the concentration of salutes in the sap with fertilizers not sure if that is just voodoo

[_Keith]

  On 1/14/2014 at 9:19 PM, Tropicdoc said:

Some people try to increase the concentration of salutes in the sap with fertilizers not sure if that is just voodoo

First technique is what I used on the alfredii, along with a blanket on top.

[amazondk]

Where I grew up in Great Falls, Montana a freeze can happen in a day. The day can start at 40 F or so and end at 20 F below zero. And, then it can warm up from 20 F below zero to over 40 F in a night.

This was a warm February day in 2013 on the Rocky Mountain Front. But, the wind still cut to the bone. No palms here.