Comparing cold hardiness in C. Humilis after 2 nights at 11F in Dallas. 
One image is the overview of the palms so you can see their placement near each other. The blue variety is C. Humilis cerifera. It is undamaged. I have 2 other large undamaged specimens in other parts of my garden. The green and common form has been defoliated and taken to the ground. We had 11F the previous winter and all the growth was from one season. Previously we had two mild decades and the trunk on this green form was 12 feet tall. 2021’s 3F, killed it to the ground. During that same winter the cerifera defoliated. But the multiple trunks remained intact. 
Seems for cerifera, minor damage  above 10F and defoliation but viable trunks between 10F and 0F. 
These are my observations in my hot summer climate and I hope by all of us sharing our personal experiences we can get a better understanding of real world hardiness of our cold hardy palms. 🌴

Tony, thank you for the information. I have grown the green form for about 20 years.   But I suspect since mine is tucked against the Southside of my house, that is what allows it to succeed.  They are not a fun one to clean up post winter.  Easy to move, hint, hint....

Thanks for this great pictorial information Tony.  I have a few around here in various sizes and I don't protect them (var. cerifera) and I'm giving up on them as they spear pull every single year.  Just not something I'm willing to invest much time and energy into.  They are beautiful when they're older, but also as poster above mentions, not fun to work close with!

15 hours ago, jwitt said:

Easy to move, hint, hint....

I had no issues moving the green form (var. humilis) but when I moved a small blue form (var. argentea - formerly var. cerifera) the main stem died and only a couple of small suckers survived.  The var. argentea seem to be somewhat temperamental when small.

Same results here, the green form gets damaged more easily during cold, damp conditions compared to the gray form. The green form grows a lot faster, though. Normally we have mild, damp winters, but in some years it can get pretty cold. This cold weather can last for a week with daytime temperatures around freezing.

Damage starts at about -10 C/14 F. I also have a volcano that is about as cold-hardy as the gray form but very slow-growing. 

All three have survived -16 C/3F in the record 2012 winter, but were defoliated. 

 

 

 

 

1 hour ago, Marco67 said:

Same results here, the green form gets damaged more easily during cold, damp conditions compared to the gray form

My experience is the exact opposite. Pacific North West wet winters in a usual year both will do fine.  In a cold year blue ones will get damage and green ones do better.  Last winter which was an extreme one, the blue ones died for me, green ones survived.  Drive around town and its rare to see a big cerifera, but green ones are somewhat common.

My experience at my old place was like Tony. My ceriffera was planted in 2005 and has grown to 9’ tall and 10’ wide with many big pups.  There is one other in the neighborhood about half that size.  
Never had any damage and I never protected.  This palm was planted by my roommate.

picture is a few years old. 

Edited January 27, 20242 yr by Paradise Found

The green and blue forms are going to vary in their hardiness.  Two greens will not be alike.  The same for blues too.  That's about all I can really say.

Edited January 27, 20242 yr by RFun

Hey Tony , 

I see your palms are making a nice recovery . 

In my climate ( and a great microclimate )  my Chamaerops humilis had frond damage after a quick 6F Low temperature   around the Christmas before  last  . In the second picture you can see its recovery after summer . My Cerifera ( in the 3rd picture ) did well and seems to have hardier fronds . Of course your palms are a lot bigger so I'm not sure how to compare them exactly  .

Will

 

 

 

 

 

 

 

 

My Chamaerops cerifera did well :

 

Edited January 27, 20242 yr by Will Simpson

When I lived in Natchez, Mississippi (a 9a climate, but on the cool side with an average 50F isotherm in January), We had a neighbor across the street with two clumps of Chamaerops humilis flanking their entry steps (I think a typical mostly green form). The 2010 3-day freeze (to 18F) as I remember did nothing to them, but the quicker freeze to 13F in February 2018 pretty much defoliated them. Here is a Google Street View of their house taken three months after that 2018 freeze.

@TonyDFW, I'm so sorry your beautiful landscape keeps getting hammered lately. Hopefully this will be the end of this string of very bad winters for Texas. At least you can call your place a true 'proving ground'...after all these years, you've proved a lot!