Can large T. Fortunei survive -5F/-20C with basic cover

[Palmlex]

Hello ,

I'm kind of tired of waiting years and years for my small palms to get to a decent size so I was planing to purchase a couple of large Trachycarpus Fortunei this spring, around 6ft tall. I know they should be fine short term, but I wouldn't want them to die after a cold blast that could get down to -5F/-20C for a few hours. Usually when that happens, temperatures stay more or less below freezing for the better part of the week, but not nearly as cold as -5F. These cold blasts should only happen once every 5+ years, but I don't wanna spend a lot of money on mature palms if they have no chance of surviving.

Does any of you have any experience with them in this kind of weather and do you think they could survive it if I wrap them with several layers of frost cloth and then maybe bubble wrap them?

If not, are there any covering methods I could use that don't involve string lights, since they'd be rather far from the house?

Thanks.

[Collectorpalms]

Lots of them died in Texas Feb 2021 after 3-7 days below 32F and ultimate lows under 5F. Mostly only ones over 6-12Ft surved. Smaller ones died and more exposed very tall ones died. Not sure any survived -5F that were not protected and heated.

Edited January 11, 2022 by Collectorpalms

[Allen]

At -5F You could put them in a foamboard box and they might live but at -5F you really need a electrical heat source.  You can also try fencing them in wrapping them and filling the cage with dry leaves and covering to keep leaves dry but it is really hard if they are over 4-6' tall.  Don't use bubble wrap.  What country/zone are you in?  Please add it to your profile.

Edited January 11, 2022 by Allen

[oasis371]

You have not posted a gardening zone. Where are you located?

Regardless, as said above, you will need to heat at that temperature, something more than a blanket. 

 

[Jimhardy]

Do you still live in Southern Romania?

[Palmlex]

2 hours ago, Allen said:

At -5F You could put them in a foamboard box and they might live but at -5F you really need a electrical heat source.  You can also try fencing them in wrapping them and filling the cage with dry leaves and covering to keep leaves dry but it is really hard if they are over 4-6' tall.  Don't use bubble wrap.  What country/zone are you in?  Please add it to your profile.

1 hour ago, oasis371 said:

You have not posted a gardening zone. Where are you located?

Regardless, as said above, you will need to heat at that temperature, something more than a blanket. 

 

15 minutes ago, Jimhardy said:

Do you still live in Southern Romania?

 

South of Romania, I believe zone should be 7a. The city I found to have the most similar climate from the US is Salt Lake City, Utah (although my climate is wetter and way more overcast in winter).

[Palmlex]

2 hours ago, Collectorpalms said:

Lots of them died in Texas Feb 2021 after 3-7 days below 32F and ultimate lows under 5F. Mostly only ones over 6-12Ft surved. Smaller ones died and more exposed very tall ones died. Not sure any survived -5F that were not protected and heated.

I know there are quite a few Fortunei in Plovdiv, Bulgaria, from where the strain with the same name comes. The climate is very similar, only slightly warmer, like half a zone I would say, which I'm hoping I could match by covering the palm fairly well.

Sounds pretty discouraging that the ones in Texas died at lows of 5F, while the ones 150 miles/250km south of me face that temperature fairly often (certainly more often than in Texas).

[Allen]

I just looked up Bucharest, Romania historical weather and temps seem pretty good for a fortunei there.  I saw one 0F but really almost no temps below 10F.  Is Bucharest a bit warmer than yours?

[Palmlex]

17 minutes ago, Allen said:

I just looked up Bucharest, Romania historical weather and temps seem pretty good for a fortunei there.  I saw one 0F but really almost no temps below 10F.  Is Bucharest a bit warmer than yours?

No, the temperatures should be pretty much the same on average, in a given year. And yes, while I think that temperatures most of the time should be able to sustain Fortunei palms, every now and then, some northern air can descend and temperatures can look like this, in Feb-Mar 2018:

Feb 26, 27, 28: Low 15F, High 22F

Mar 1: Low 1F, High 30F

Edited January 11, 2022 by Palmlex

[Allen]

15 minutes ago, Palmlex said:

No, the temperatures should be pretty much the same on average, in a given year. And yes, while I think that temperatures most of the time should be able to sustain Fortunei palms, every now and then, some northern air can descend and temperatures can look like this, in Feb-Mar 2018:

Feb 26, 27, 28: Low 15F, High 22F

Mar 1: Low 1F, High 30F

15F is no problem for established fortunei even with the 22F high.  If it stays wet there you always have to look out for rot if that is a issue in your area like it is for me.  The March 1st 1F one though might defoliate or kill.  Covering it completely might save it in this brief dip like I see in your temps down to 0F.   Safer to have the lights or a heating cable handy with a burlap or frost cloth wrap over them and preferably on a thermocube.

Edited January 11, 2022 by Allen

[Palmlex]

14 minutes ago, Allen said:

15F is no problem for established fortunei even with the 22F high.  If it stays wet there you always have to look out for rot if that is a issue in your area like it is for me.  The March 1st 1F one though might defoliate or kill.  Covering it completely might save it in this brief dip like I see in your temps down to 0F.   Safer to have the lights or a heating cable handy with a burlap or frost cloth wrap over them and preferably on a thermocube.

Yeah, I'll have to watch out for rot, because winters are weird here. Some are sunny and, I was gonna say pleasant, but I don't like winter, so I'm just gonna say tolerable, and some winters it rains every day for 2 weeks.

Edited January 11, 2022 by Palmlex

[oasis371]

For a predicted  minimum of 10 F.. I protected my Trachy with a plant collar filled with insulating fabric, then bungeed the bottom with a thick, moving blanket, I bungeed the top with a shower curtain..., having brought the fronds together around the center spear.  Then, I put a light, black plastic garbage can over it.  It is on the south side of the house too., but I did not use lights.  I hate the cold too, but thankfully, this kind of deadly cold is not so typical, but always memorable!

[Jimhardy]

3 hours ago, Palmlex said:

 

Sounds pretty discouraging that the ones in Texas died at lows of 5F, while the ones 150 miles/250km south of me face that temperature fairly often (certainly more often than in Texas).

If I recall correctly Texas had a pretty "warm" winter up to the point the

cold hit so the palms were probably still growing and really never "hardened" off for winter.

[oasis371]

Jim, I don't think palms ever "harden off" for winter...., but they may have been in active growth when the cold hit, if that's what you mean.
 

 

Edited January 11, 2022 by oasis371

[Jimhardy]

They do harden off, mine always take the cold in spring better than in fall because they have seen some...

every living thing on this earth makes some adjustment to the cold or its no longer a living thing on earth.

 

Many years back John in Colorado did some amazing work on cold hardiness in Trachys,Sabal and some

other cold hardy palms, they even put leaves in freezers and figured out their true

hardiness but there were many factors that went into it,as I recall volumetric soil moisture was also a big factor for

Trachys but this was different for the palms of the southeast US like Needle palms and Sabal

To bad he is not "around" anymore, his Trachy was sabotaged and he had to put up with

constant mutant comments from the peanut gallery....they weren't even palm growers.

 

[Palmlex]

5 hours ago, Jimhardy said:

They do harden off, mine always take the cold in spring better than in fall because they have seen some...

every living thing on this earth makes some adjustment to the cold or its no longer a living thing on earth.

 

Many years back John in Colorado did some amazing work on cold hardiness in Trachys,Sabal and some

other cold hardy palms, they even put leaves in freezers and figured out their true

hardiness but there were many factors that went into it,as I recall volumetric soil moisture was also a big factor for

Trachys but this was different for the palms of the southeast US like Needle palms and Sabal

To bad he is not "around" anymore, his Trachy was sabotaged and he had to put up with

constant mutant comments from the peanut gallery....they weren't even palm growers.

 

Do you remember if soil moisture was a positive or negative factor? I know that most palms hate wet frosts, but Trachys generally seem to thrive even in very wet environments.

[Jimhardy]

It was better for the Trachys to be bone dry and to start this if possible

before it would get really cold(not practical for most )as this helps with 

them "hardening" off as growth slows.Interestingly the Sabal and Needle palms

seemed to be ok with wetter soil as I recall.

[buffy]

23 hours ago, Collectorpalms said:

Lots of them died in Texas Feb 2021 after 3-7 days below 32F and ultimate lows under 5F. Mostly only ones over 6-12Ft surved. Smaller ones died and more exposed very tall ones died. Not sure any survived -5F that were not protected and heated.

Most of the T. fortuneis in Longview survived the -5F unprotected, but it was scary.  I had a 10 footer wait until May before anything started happening. All the waggies died. 

[Jimhardy]

It can be somewhat impractical but I wonder what % of palms could have been saved

by a little operation on/above the growth point.....oh well, the south is the big leagues when it comes to palms

and sometimes they are just to big but some of these guys that are so busy over trimming palms

 could look into saving these palms(or at least trying to) rather than massacring their summer growth..

[Collectorpalms]

1 hour ago, buffy said:

Most of the T. fortuneis in Longview survived the -5F unprotected, but it was scary.  I had a 10 footer wait until May before anything started happening. All the waggies died. 

Longview had it better than central Texas up until the night of the 16th, where it dropped below 0 between 430am until 745am. We had much longer duration of colder temperature than far east texas. Waco and Cities south of Dallas were as low as -6, and most were dead unless they were protected from the wind. by a hotel etc.. Lot of people have commented on here of their dead Trachys in Dallas, There were dead trachycarpus near me and I was "only +4" 

Edited January 12, 2022 by Collectorpalms

[EJPalm05]

I think that the t fortunei can survive to -5F if it is In a sheltered area and 0F if it is in the open!

[Allen]

38 minutes ago, EJ NJ said:

I think that the t fortunei can survive to -5F if it is In a sheltered area and 0F if it is in the open!

If it survives at 0F or -5F it will be a tent pole taking a long time to recover if not go into permanent decline.  Below 8F - 10F they start taking frond damage

Here is a reference article in addition to my experiences

https://edis.ifas.ufl.edu/publication/MG318

[oasis371]

I agree with Allen, there are definite issues at temps from 0 to -5 F... You will have a lot of foliage burn if not complete bud loss.  Some questions to ask...,

1.) Is the plant in a microclimate?

2.) What is the sun exposure like? (Tons of winter sun is not necessarily a good thing.)

3.) How long does the cold last?

4.) Are there also issues with wetness?

5.) How old is the plant? And how long was it established?

6.) Individual  plant genetics

7.) What is the overall health of the palm?

I am concerned about a minimum of 10 F, so I double wrapped mine and then threw a black, plastic garbage can over it.  Alleviating factors include..., relatively mild days before (over 40 F.) and relatively short duration.  

 

 

Edited January 12, 2022 by oasis371

[Allen]

32 minutes ago, oasis371 said:

I agree with Allen, there are definite issues at temps from 0 to -5 F... You will have a lot of foliage burn if not complete bud loss.  Some questions to ask...,

1.) Is the plant in a microclimate?

2.) What is the sun exposure like? (Tons of winter sun is not necessarily a good thing.)

3.) How long does the cold last?

4.) Are there also issues with wetness?

5.) How old is the plant? And how long was it established?

6.) Individual  plant genetics

7.) What is the overall health of the palm?

I am concerned about a minimum of 10 F, so I double wrapped mine and then threw a black, plastic garbage can over it.  Alleviating factors include..., relatively mild days before (over 40 F.) and relatively short duration.  

 

 

10F on one night is generally ok for larger established palms unprotected but freezing water in the crown at those temps unprotected may still cause rot/spear pull in March/April if not managed.  Small pot sized palms (Say under 4' OA)  may die/spear rot, etc with temps from roughly low twentys F and down.  I don't consider Trachy good and cold hardy unless they

-have a Full diameter trunk

-have been planted for a couple years

-are growing vigorously (10+ fronds/year)

Edited January 12, 2022 by Allen

[DallasPalms]

There are several factors I think. Nearby some neighbors of mine had their driveway lined with many Trachycarpus that most would call fortunei. Closer to their front door an arrangement of another type with fancier looking 'hair' and stiffer fronds..  so anyhow they were the prettiest in DFW I think and then Uri came through right after they moved... I didnt go by around that time but I assume that the new owners did not protect them...

Out of a dozen or so I only saw 3 or 4 grow back several months after Uri like maybe late summer and fall of this past year...  I noticed alot of different traits... I collected seeds from 3 of them and noticed they had 3 different sized seeds and alot varying traits.. one had a Takil looking leaves that were wider I think maybe a gap in between the center leaflets...another was the more floppy leaf type during heat but perked up after rains, and some of the shorter ones with nicer hair and stiffer darker green fronds might have been waggy or waggy hybrids

And so those were the ones I saw that returned.. our low temp was 2F with a few days below 20f and around a week below 32f total.  We had a few that did fine and 75% or so pooped...

Another member mentioned our soil... I suspect the same with cacti which can have mineral specific traits for adapting (and also like humans) it's possible that a complete soil with certain minerals might add to cold hardiness but genetics also weigh in heavily more than anything. And even with gene variation, a plant line with a history may be producing some of the hormone effect that leads to early dormancy (for some tree types) and the percentages will vary.. and we just never know unless the weather changes... I was reading about apple rootstocks for grafting the ones that go dormant sooner have a real effect on the hardiness of the top of the tree... probably similar with palms if they trigger into sleep... some maybe better prepared for a winter fluke ..but I'm not 100% sure about what matters most besides genetics with palm trees

Also I wonder if my neighbor had different soil put In when they built the house. We are a black clay area but i see orange dirt on his lot and so maybe that had some effect on minerals and moisture... some places may have dried out alot more ... i doubt the moisture being a factor because they were all fairly tall maybe 9-10 feet and taller... @ deep established roots

And so with some Genetics you can get a high percentage that will tolerate temps that low and some a lower percentage and then the other factors maybe playing a role also @ nutrition, timing, heat factor during the summer, other stressors, micro climates etcetera etcetera

Edited January 13, 2022 by DallasPalms

[Palmlex]

22 minutes ago, DallasPalms said:

There are several factors I think. Nearby some neighbors of mine had their driveway lined with many Trachycarpus that most would call fortunei. Closer to their front door an arrangement of another type with fancier looking 'hair' and stiffer fronds..  so anyhow they were the prettiest in DFW I think and then Uri came through right after they moved... I didnt go by around that time but I assume that the new owners did not protect them...

Out of a dozen or so I only saw 3 or 4 grow back several months after Uri like maybe late summer and fall of this past year...  I noticed alot of different traits... I collected seeds from 3 of them and noticed they had 3 different sized seeds and alot varying traits.. one had a Takil looking leave that was wider I think maybe a gap in between the center leaflets...another was the more floppy lead type during heat but perked up after tsins and some of the shorter ones with nicer hair might have been waggy or waggy hybrids

And so those were the ones I saw that returned.. put low was 2F with a few days below 20f and around a week below 32f total.  We had a few that did fine and 75% or no pooped...

Another member mentioned our soil... I suspect the same with cacti which can have mineral specific traits for adapting (and also like humans) it's possible that a complete soil with certain minerals might add to cold hardiness but Gene's also weigh in heavily more than anything. And even with Gene's a plant line with a history may be producing some of the hormone effect that leads to early dormancy (for some tree types) and the percentages will vary.. and we just never know unless the weather changes... I was reading about apple rootstocks for grafting the ones that go dormant sooner have a real effect on the hardiness of the top of the tree... probably similar with palms if they trigger into sleep mode some maybe better prepared for a winter fluke ..but I'm not 100% sure

Also I wonder ifbmy neighbor had different soil put In when they built the house. We are a black clay area but i see orange dirt on his lot and so maybe that had some effect on minerals and moisture... some places may have dried out alot more ... i doubt that being s factor because they were all fairly tall maybe 9-10 feet and taller...

And so with some Genetics you can get a high percentage that will tolerate temps that low and some a lower percentage and then the other factors maybe playing s role also @ nutrition, timing, heat factor during the summer, other stressors, micro climates etcetera etcetera

Genetics could definitely also play a role, but I believe, and this is just my uninformed opinion, I believe that climate could play a role in their hardiness too. Since in Dallas average highs are over 60F in February, which is a temperature they could actively grow at, I believe there's a chance that could prevent them from fully hardening, if that's even a thing. Maybe they do need to experience low temperatures to be ready for winter. So if they're used to 60F in winter and then all of a sudden temperatures plummet to single digits, maybe they're not ready to handle all that cold.

Another kind of variation due to climate can be seen in mature specimens, where they seem to grow thicker trunks when grown in colder climates.

Edited January 13, 2022 by Palmlex

[DallasPalms]

52 minutes ago, Palmlex said:

Genetics could definitely also play a role, but I believe, and this is just my uninformed opinion, I believe that climate could play a role in their hardiness too. Since in Dallas average highs are over 60F in February, which is a temperature they could actively grow at, I believe there's a chance that could prevent them from fully hardening, if that's even a thing. Maybe they do need to experience low temperatures to be ready for winter. So if they're used to 60F in winter and then all of a sudden temperatures plummet to single digits, maybe they're not ready to handle all that cold.

Another kind of variation due to climate can be seen in mature specimens, where they seem to grow thicker trunks when grown in colder climates.

That does make sense @ weather triggering and hormones. There are a few ppl advertising some northern grown trachycarpus that have survived Tennessee winter, I think maybe Orgeon... it could very well be that some from hotter climates are weakened a little by hotter climates... we regularly see 100f and high 90f every year in July August sometimes alot earlier.. we warm very quickly too... I do see a few scattered all over Dallas however so I lean towards Genes and nutrition being thr primary factors

But I'll add that the Wagnerianus looking ones did fine and again they maybe waggy hybrids or something else. One I collected seeds from had noticeably larger seeds than every other Trachy seed I've seen so far. Stiffer fronds darker green color, fancy hair ... also shorter and more stout... could also mean younger tree or a different cultivar or hybrid altogether ...

the floppy leaf type had the smallest leaves,  and the tallest with takil-like leaves had medium sized seeds, maybe 50-100% larger... the waggy lookers were maybe 2-3x larger sized seeds than the medium sized... and it was one of the few that grew some new leaves many months later... the ones around it grew several new leaves.. 

Edited January 13, 2022 by DallasPalms

[jwitt]

I know of no local unprotected trachies(larger size5'+) that died here in 2011. 2 consecutive nights below zero and a high of +7f.  Mine saw -10f low/7f high/ -3f low in a 36 hour period.  Although they did lose all leaves, they did resume growth in spring.

 

Your results may vary.

 

P.s. I saw some come back from back to back nights of -11f. 

Here is central NM.

 

Palms may not harden off as such but they can definitely hibernate. Exactly how filifera survive eon's of fire and/or drought.

Edited January 13, 2022 by jwitt
Additional info

[oasis371]

Coming back from -11 F. would be extraordinary, if accurate.  I do think that NM's drier climate does offer some hardiness advantages, which is why I think in addition to protecting from subarctic cold, whatever can be done to protect the crown from moisture is probably also useful. 

It occurred to be today, on a relatively mild January day (upper 40's), that the weather conditions both before and after subarctic temperature drops are also really, really important.  So my high temperature today of near 50 F. meant that there was available liquid water available for my Trachy, and that the ground temperatures were able to warm.  So now, when that second arctic front passes tomorrow and it bottoms out at 13 F, the ground will still be  relatively mild.  Then, after the arctic air mass moves on out, that upcoming blockbuster, southern snow/sleet/freezing rain storm is supposed to move in here as a a big rainstorm at the coast.

Edited January 13, 2022 by oasis371

[jwitt]

5 hours ago, oasis371 said:

Coming back from -11 F. would be extraordinary, if accurate.  I do think that NM's drier climate does offer some hardiness advantages, which is why I think in addition to protecting from subarctic cold, whatever can be done to protect the crown from moisture is probably also useful. 

It occurred to be today, on a relatively mild January day (upper 40's), that the weather conditions both before and after subarctic temperature drops are also really, really important.  So my high temperature today of near 50 F. meant that there was available liquid water available for my Trachy, and that the ground temperatures were able to warm.  So now, when that second arctic front passes tomorrow and it bottoms out at 13 F, the ground will still be  relatively mild.  Then, after the arctic air mass moves on out, that upcoming blockbuster, southern snow/sleet/freezing rain storm is supposed to move in here as a a big rainstorm at the coast.

Filifera also survived. 

We do not have the extend freezes that N Texas does, but much sharper cold.  It remained below freezing for 4 days with a 40+. hour period never above 9f

The water table at the -11f locale is under 5 feet. It rained and snowed on these unprotected palms at the onset of the Arctic outbreak and did not melt for sometime.

But a telephone pole feels warm to the touch on a 15f degree day here as most days are sunny unlike east of here.

Trachy is on the right side of house. 

Side point, it saw zero or below the following winter. Pic from 2018.

 

Edited January 14, 2022 by jwitt

[Palmlex]

3 hours ago, jwitt said:

Filifera also survived. 

We do not have the extend freezes that N Texas does, but much sharper cold.  It remained below freezing for 4 days with a 40+. hour period never above 9f

The water table at the -11f locale is under 5 feet. It rained and snowed on these unprotected palms at the onset of the Arctic outbreak and did not melt for sometime.

But a telephone pole feels warm to the touch on a 15f degree day here as most days are sunny unlike east of here.

Trachy is on the right side of house. 

Side point, it saw zero or below the following winter. Pic from 2018.

That's pretty amazing they can survive those temperatures. I wish winters weren't so miserably wet and overcast here.

I'm also amazed by how good that Trachy seems to look in an arid environment. I'm guessing they need supplemental water or do they make it on their own?

[Jimhardy]

3 things going on in the west, more intense sunlight and dry air both

are enemies of fungal growth, if a palm has a chance to survive intense cold

these 2 factors are biggies. Another thing that helps is in the drier air you get 

lower night temps as the day length decreases, this helps the palm slow down and

this causes the more tender new growth to become tougher, hardening off.

It would be great if you don't know about this that you don't comment on it-

it really doesn't matter what your FEELINGS are because its the facts that kill

palms and not feelings. 

[jwitt]

13 hours ago, Palmlex said:

That's pretty amazing they can survive those temperatures. I wish winters weren't so miserably wet and overcast here.

I'm also amazed by how good that Trachy seems to look in an arid environment. I'm guessing they need supplemental water or do they make it on their own?

The water table at that location is under 5'. And that water availability is very localized. It does not need supplemental water once established.

 

That is not true in 99% of the other parts of the metro(Albuquerque). They will die in a short time.

 

We are also a mile high in elevation, which increases solar radiation. And other things!

That Trachy pic is 3/2018- so coming out of winter with water soaked roots. Or at least, water available to the roots at all times.

Sorry- that pic is not March. I do have one, the filifera are brown, Trachy untouched. 

 

Edited January 14, 2022 by jwitt
Additional info

[Jimhardy]

A story...

One day, there was little Bizzy on my porch, he was bone dry and I mean bone dry.

It got down to 20F,I brought it up into the house that morning, with not much of any water

in the palm and the humidity being sub 20% inside the spear never pulled as it grew out,

there was a dead spot in the spear, it just broke off as it came out-there was no moisture for

any fungus to live off of, so the material just died rather than fungus showing up because there was not moisture to feed it.

 

In the southwest you have,solar radiation,air movement and drier air,ail of these

are the enemy of fungus...dont feed it and it dies.

Edited January 14, 2022 by Jimhardy

[maskedmole]

My location is zone 6b according to the 2012 usda map. But we are 7a in the 2015 map and recent years I have averaged my area as a weak zone 7a averaged at around 4 degrees Fahrenheit. That being said, some years we may get down to around zero degrees. Other years our lowest temp may be over 10 degrees. You can see in my signature. I grow windmill palms and my oldest one is around 3 or 4 years old I have had in the ground. It only defoliated it's first winter around 13 degrees when I just threw a little rag over it lol. Now with it being established in the ground, I'm quite certain it can survive lower temperatures without defoliating. It has survived down to around zero degrees with a basic cover. Several times it has survived teens or single digits with basic cover with the lowest being around zero. 

What I do now is I put a couple blankets over it, one being lighter and the other a pretty heavy comforter. Then I just put a tote over top and weigh it down with a big rock or something, maybe even bungee cord it down when the temperatures forecast it going into the teens or below. I try to do it when it is dry before any freezing rain or snow comes so it isn't just stuck under there being all froze up.. It has been quite happy and survived many winters with no damage. I have a couple seedling trachy's and one about a foot tall more newly planted and they are all doing okay with basic cover. So far this winter we have gotten down to 7 degrees about and all my palms are looking good with just my simple methods. 

That being said, my trachycarpus palms are still quite small. My biggest and oldest being maybe knee high or so with many leaves. I'm really not sure what I'll do when they start getting 6ft tall plus but I'll figure it out when I get there. Maybe I'll just tape up some big heavy blankets, tie up the leaves and just place totes on top when it gets really cold lol. Or maybe a full on wrapping every winter. I'll figure it out when I get there. I'm quite certain my methods would still work if it got some degrees below zero even 5 below. Just double or triple up the blankets. Very cold daytime highs are also not very good if it is below freezing many days in a row so you have to think about that too. Not sure about ventilation if this helps much or matters but I usually try to open up the enclosures a bit if it has been 5 days or more on the warmest day. 

Edit: Oh my bad, so I see you are asking about 6ft tall palm trees. Anything under 10 or 15 degrees is when damage might occur to leaves. Under 10 and you are taking a gamble. I don't know much about the bigger palm trees and wrapping methods but based on my little experience, I would say at negative 5 degrees you would need the equivalent of 2 or 3 large heavy comforters for the palm tree to survive. At 10 degrees, maybe the equivalent of 1 or 2 heavy comforters. Sorry I don't know how to delete this so I thought I would make up for my lack of reading the the description fully. At that large of size, you might be better off wrapping the full winter, and yes I do think it can be done without too much difficulty as other people in colder areas do this without too much hassle as far as I can see. Your method might work if the palm is located in a sheltered area away from harsh cold winds.

Edited January 14, 2022 by maskedmole

[Palmlex]

1 hour ago, maskedmole said:

My location is zone 6b according to the 2012 usda map. But we are 7a in the 2015 map and recent years I have averaged my area as a weak zone 7a averaged at around 4 degrees Fahrenheit. That being said, some years we may get down to around zero degrees. Other years our lowest temp may be over 10 degrees. You can see in my signature. I grow windmill palms and my oldest one is around 3 or 4 years old I have had in the ground. It only defoliated it's first winter around 13 degrees when I just threw a little rag over it lol. Now with it being established in the ground, I'm quite certain it can survive lower temperatures without defoliating. It has survived down to around zero degrees with a basic cover. Several times it has survived teens or single digits with basic cover with the lowest being around zero. 

What I do now is I put a couple blankets over it, one being lighter and the other a pretty heavy comforter. Then I just put a tote over top and weigh it down with a big rock or something, maybe even bungee cord it down when the temperatures forecast it going into the teens or below. I try to do it when it is dry before any freezing rain or snow comes so it isn't just stuck under there being all froze up.. It has been quite happy and survived many winters with no damage. I have a couple seedling trachy's and one about a foot tall more newly planted and they are all doing okay with basic cover. So far this winter we have gotten down to 7 degrees about and all my palms are looking good with just my simple methods. 

That being said, my trachycarpus palms are still quite small. My biggest and oldest being maybe knee high or so with many leaves. I'm really not sure what I'll do when they start getting 6ft tall plus but I'll figure it out when I get there. Maybe I'll just tape up some big heavy blankets, tie up the leaves and just place totes on top when it gets really cold lol. Or maybe a full on wrapping every winter. I'll figure it out when I get there. I'm quite certain my methods would still work if it got some degrees below zero even 5 below. Just double or triple up the blankets. Very cold daytime highs are also not very good if it is below freezing many days in a row so you have to think about that too. Not sure about ventilation if this helps much or matters but I usually try to open up the enclosures a bit if it has been 5 days or more on the warmest day. 

Edit: Oh my bad, so I see you are asking about 6ft tall palm trees. Anything under 10 or 15 degrees is when damage might occur to leaves. Under 10 and you are taking a gamble. I don't know much about the bigger palm trees and wrapping methods but based on my little experience, I would say at negative 5 degrees you would need the equivalent of 2 or 3 large heavy comforters for the palm tree to survive. At 10 degrees, maybe the equivalent of 1 or 2 heavy comforters. Sorry I don't know how to delete this so I thought I would make up for my lack of reading the the description fully. At that large of size, you might be better off wrapping the full winter, and yes I do think it can be done without too much difficulty as other people in colder areas do this without too much hassle as far as I can see. Your method might work if the palm is located in a sheltered area away from harsh cold winds.

Hey, thanks for your reply. I'm glad you didn't delete it, because it was your experience, a success story and quite informative.

I believe the smaller ones are able to survive just being covered due to the heat released by the ground. And that might not be enough for taller ones, as you're actually describing in your post too. What I have found works really well for some of my other palms is put as much water mass as possible near them (in large containers) and insulate the whole thing as well as you can.

I don't have any palms taller than 5' currently, but I was also considering covering them in such a way that the top of the enclosure is way narrower than the base. Like an upside down cone or a teepee. That gives me enough room to place water jugs that can release latent heat during the coldest nights and it also reveals more soil which can release heat as well, while the top has as little surface area as possible to minimize heat loss. All this would be pointless without great insulation though.

The water containers might not be a viable method for very cold climates where they would quickly freeze. Mine didn't get even close to freezing yet.

Small note: Don't leave transparent water jugs in the sun. If the shape is just right, they could act as a lens and burn something. And no, I'm not talking from experience, but I like to be cautious.

Edited January 14, 2022 by Palmlex

[SeanK]

I have found that palms purchase bare-root or balled & burlapped are less cold hardy than those planted out from pots. There is some strain on the plant as it recovers root mass.

[smatofu]

1. The younger/smaller palm you buy, the better it establishes itself, the better it can survive winters. Patience is the name of the game in growing palms in cold climate.

2. For temp -5F, you need to wrap and maybe provide some heating. Careful! It is easy to freeze the palm, but even easier to cook it. Never wrap in any plastics. 

[Palmlex]

15 minutes ago, smatofu said:

1. The younger/smaller palm you buy, the better it establishes itself, the better it can survive winters. Patience is the name of the game in growing palms in cold climate.

2. For temp -5F, you need to wrap and maybe provide some heating. Careful! It is easy to freeze the palm, but even easier to cook it. Never wrap in any plastics. 

I already have small ones and I'm eager to watch them grow over time, but instead of waiting 10 years before I have something that resembles a trunking palm, I'd prefer also getting some that already have a decent trunk.

[smatofu]

12 minutes ago, Palmlex said:

I already have small ones and I'm eager to watch them grow over time, but instead of waiting 10 years before I have something that resembles a trunking palm, I'd prefer also getting some that already have a decent trunk.

Plant them in good soil (soil + cow manure {not too much} + sand) and they will grow very fast. You will get 10 feet or more in 10 years.

The older the palm, the more difficult for it is to well establish. Transplanting is just a huge stress for palms and many never recover. This is from my experience and from watching tens of palm trees in my neighborhood. 

Edited January 21, 2022 by smatofu