I'll just post what I posted there 😀

Same here as Stosh,18 caused spear-pull on at least one of my Trachys a few years back,one caveat-
it had not been cold before that and had rained right before this temp.

Last year we had almost no cold-avg Oct/Nov 42/56,it was 61 on December 1

The rest of the month averaged 20/32 about half my Trachys were damaged and half of that almost finished off!

As john in Colorado has brought up,palms being hardened off are a whole different animal,
my Trachys can easily handle single digits if they are brought down gradually- by the end of Jan if they are still
in good shape...single digits cause zero damage.

Stosh
Thanks for the info on the Washys,mine saw 23f last night,I think that is about as cold as I
want them to see as I do want to overwinter with healthy leaves!

BTW-
My Robusta had some minor blackish green streaking,Filifera nothing.
Both were fine when the temp went above freezing-no visible damage.

Yet another novice question: what is this "big board"? Can you give a link to your thread there?

http://members3.boardhost.com/HardyPalm/

It looks like my title for this thread was too long! I also forgot to mention that I asked for scientific articles but no one came forward.

Paul, that post on the big board was spot on. I wish more people answered your question as it was better then the weather maps that seemed to be a hit topic. Reason why I don't post on that board to often.

Neadles and sabal minor with a trunk wrap of wall of water with hay pack did great with a low temp of 3.6 in my coldest location last year. Hay pack did more harm then good in my opinion though. This year I'll just use wall o water around the trunk to keep moisture down. 3 large trachies endured 10+ days below freezing and at least 10f for a low with no damage other then a small burn ring in the spring. They where covered from all wind and moisture but endured the coldest week and a half of the year with 0 heat.

Thanks for your post as it was a top notch one!!!

Bill

Paul,
that is the "big board"? I'm with Bill--I don't find it that useful. I posted a couple of replies so you know who I am there.
Try this thread on http://www.palmsociety.org.uk/forum/ as they have a lot of folks in northern Europe, including up to Norway and Sweden. They also grow the palms on your list.
As for scientific papers, please let me know if you find some. I'll do some library work on this topic in January when I have some time. If you want to collaborate on a formal project, PM me.
As to your original question, I have data for you about Phoenix roebellini (pygmy date palm). Mine has been in the ground since April. I planned to dig it up and pot it to bring in but have not yet. Well, last night we got down to 26 oF (3 oC) and were below freezing for about 7 hours. I did not see damage this morning, but by dusk today the fronds--all of them--looked brownish and were curled up. In short, it looks like toast. I have all the other palms on your list and they look fine today. I was delighted that Chameadorea radicalis also look good, as does Sabal mexicanum. I plan to give these good protection when I have time....

"I was delighted that Chameadorea radicalis also look good, as does Sabal mexicanum. I plan to give these good protection when I have time...."

Thanks for that Erik. If you do dig up some articles, I'd be delighted to read them through...

Bill- Thanks for that. The time below freezing issue is poorly understood and your info on that is very useful. I do wonder what would happen if you set a T. fortunei at -5C for 2 months. Would it make it out OK? Does it need occasional temps above 0 to get liquid water? Or, would this just be like setting it up outdoors and not watering it for 2 months?

The Hay pack was something that was advocated a few years back, and if you've seen the book "Hot plants for cool climates" it is featured as one the main ways to overwinter palms in the north. I think that your observations are the same as what I noticed. Hay makes a decent mulch, but if it contacts the leaves, you're in trouble. Rot city. I noticed the same thing with Sabal minor, even in leaf piles the excess mositure was enough to kill them. The wall-o-water would be good since it keeps the plants dry while providing protection from the cold temps. If I ever get the time I have some 4-5 year old Sabals that I should plant out and try with something like that.

Hay is my main protection method as it is basically free here on the farm.
It does lead to rot. I used to kill palms this way.
Last winter my solution was to change the hay regularly. Basically, whenever the weather warmed up, I took it all off and replaced with fresh hay. That method worked for me. A bit of work, and not practical for folks who don't have a barn full.
As for scientific articles, here is the one I'm going over now:
http://www.cefe.cnrs.fr/fe/pdf/2007_Walther-etal_GEB.pdf
I'd like to do something similar with Sabal minor but would need help.
--Erik

Paul, I keep toying with the idea of using the t2 thermocube which turns on at 20f. Most likely I would be ok since all three of mine are 10 tall with huge carb reserves, place if the sun is out they get it all day which would easily heat the huts to above freezing. I'll most likely try it and let you know in the spring, there's way to many watts being used in the basement this year I need to conserve somehow.

Two months below freezing even at -5c would do them in I suspect. I've never done it so I can't tell you for sure, just a hunch.

Bill

These might be worth a look, if they can be found. Principes might be difficult to locate online, however.
Larcher, W. & Winter, A. (1981) Frost susceptibility of palms:
experimental data and their interpretation. Principes, 25,
143–152.

McPherson, K. & Williams K. (1998) The role of carbohydrate
reserves in the growth, resilience, and persistence of cabbage
palm seedlings (Sabal palmetto). Oecologia, 117, 460–468.

Parker, N. (1994) Northern limit of palms in North America:
Trachycarpus in Canada. Principes, 38, 105–108.

Sakai, A. & Larcher, W. (eds) (1987) Frost survival of plants.
Responses and adaptation to freezing stress. Ecological Studies:
Analysis and Synthesis, Vol. 62. Springer, Berlin

Winter, A. (1976) Die Temperaturresistenz von Trachycarpus
fortunei Wendl. und anderen Palmen. Diss. University of Innsbruck,
Austria.

"palm tree leaves have very little or no hardening capacity".

"Since hardening is an active process that depends on assimilate level in the tissues, all conditions that deplete the pool of assimilates in the tissues reduce hardening."

from here: http://www.fao.org/docrep/008/y7223e/y7223e0a.htm

Thanks, Barb. You can find anything on the web!
You, too, Paul. I'm busy now but will try to get our ILL librarian working on those as winter reading.
I'm also trying to go through the literature on genes related to cold resistance in plants.
Here is a press-release related to one of the articles on my to-read list:
http://www.sciencedaily.com/releases/2010/08/100826141213.htm
--Erik

Hi Paul,

I've never had a palm survive a winter unprotected. Although we don't get all that cold here in USDA 6b, we get WAY too much rain/snow. We average 4" (10 cm) of precipitation per month in winter. The combination of cold/wet is death. I typically mess with smaller specimens (that is less than 5 gallon in size)................it will be nice to hear others who have mature specimens like Bill MA. All we need to do is to have Bill not protect his palms and then we'll find out how hardy they really are. The reason I grow Yuccas is because the palms couldn't survive here......(I think Yucca rostrata is the best thing since sliced bread since it looks tropical, it trunks, there is NO maintenance at all, and it relatively hardy here). I try to protect my rostrata from moisture but several winters I have not protected and it did fine.

Paul,
I agree. I'm technically USDA 6 b but keep pretending I'm in 7a.
I'd like to think that needle palms will be fully hardy once they get established.
A local garden has a bunch of Sabal minor which have had no protection at all (not even extra mulch) for 20+ years and they are getting weedy, so that is probably the way for me to go.
I doubt I will ever leave Trachy unprotected....
--Erik

Erik (and everyone):

Here is the best quote from the article that Erik posted above:

"There is no single mechanism involved in plant freezing tolerance, Moellering added, so he can't say that his findings will lead any time soon to genetic breakthroughs making citrus or other freezing-intolerant plants able to thrive in northern climates"

Personally, I don't feel that there is a dormant cold tolerance pathway in all plants. Even if the genes exist in the genome, if they haven't been useful for generations, it is unlikely that the pathway could be 'turned on' easily... I do have a PDF of the original article above and will look it over in the next couple days.

I may start a new thread to address the lower threshold for Trachycarpus survival. It makes sense that GDD requirement would increase with a lower average monthly temperature for the coldest month, but it seems to me that the numbers could be shifted downwards a little... Thoughts?