"blue" form means the "desert" form. The desert means a very wide temperature variation. I think my guess is simple but truly. Can't express more detailed 'cos lack of English in 0.23 a.m. Going sleep now.

NOT a scientific answer, not being a botanist.
But, with that caveat, my GUESS is that the "blue" is a result of wax, and that the wax also protects from the desiccation associated with freezing.

...not that I'd stake the life of Bizzie on my being correct! 😆

I don't think the blue forms are always hardier...
supposedly the green form of Mazari is hardier
and I believe some other palm from the southeast U.S. -at least 🙂

Jim, I think genetics plays an equally important role.

Barb, the waxy coating on silver palms works as an inhibitor against desiccation and high levels of U.V. It also lowers the lethal freeze temperature for coated tissue thus requiring lower temperatures or a longer freeze period to cause cellular death.

Yes, I forgot Bizzie is an excellent blue example!
For extreme heat tolerance...doubt it's cold hardy.

Which leads me to guess that a blue plant is either winter hardy OR summer heat protected.
Or are there specific blue waxy plants that are both?

and high levels of U.V

wondering why my D.spinulosum--which is bluer and waxier than any other plant I have--got so sunburnt this summer when it received the same conditions this year as it has every other year. Yet it certainly isn't winter hardy.

Interesting discussion, thanks folks.

Barb

Yucca rostrata takes heat and cold -- why I bought 2 in 2011.

Also, I think C. humlis cerifera is tough. Well, I've merely killed them, personally, but think they are worth trying again. 😳

Anyway, I think there is something to the legen of blue plants....

Barb, I can only guess at your circumstances, but I've seen palms grown indoors and brought outside without proper acclimatization. I've also seen them damaged from sunlight that someway focused through glass like a magnifying lens onto a palm's leaves.

My (potted) Bizzy has seen mid 20s(F) while on the porch.

Jim,
amazing! My Bizzie insists it is a zone 10, preferably 10b, palm. It has shown damage from even the lightest frost.
I think they are individuals. Mine was grown in Homestead Florida. It wants to go home 😀

brought outside without proper acclimatization. I've also seen them damaged from sunlight that someway focused through glass like a magnifying lens onto a palm's leaves

Yes, I'm guilty of poor acclimatizing, especially with my Cocos nucifera which almost died this year.

Re the "focused through glass" comment, I thought glass prevented UV ray damage by stopping its transfer, especially the newer windows.
We replaced house windows a couple of years ago, and on a sunny day, rooms aren't as bright (noticeably).

Mine was grown in Homestead Florida. It wants to go home

Convinced Erik's hit the nail on the head.
Origin--and growing conditions (shade/sun) at the nursery--determine how a plant will behave for a long time.
I recall the "stretched" sabals. from having been grown in shade?

Jim, I frankly don't know HOW you "do it"!!!
The success of your plants (i.e. Bizzie mid-20's) breaks all the known rules.

Jim, I frankly don't know HOW you "do it"!!!
The success of your plants (i.e. Bizzie mid-20's) breaks all the known rules.

I have heard of other Bizzie's surviving to 20F.

I think it needs to be bone dry,mine was set back near the house
so,no wind or frost formation.

How about this "don't know how you do it"......my big Jade plant is
dead,I left it out for to many freezes.....it survived 23F one night
but has been damaged by longer freezes at higher temps.

If that picture was taken today, Jim, you're proving MY point 😆 😆 😆

Some nice stuff there!

Barb