Trees that are Heat Intolorant

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#1
Since it is the peak of the summer season, and this is the time a year where we bonsai practitioners deal with hot conditions the most, I thought it would be interesting and perhaps helpful to discuss trees which have been found to be, to varying degrees, heat intolorant when grown in pots.

The best example I have to start out this discussion is Fraser fir (Abies fraseri). This one, I have found is extremely heat intolorant, moreso than many boreal species of conifer. About 8 years ago, while living in Fl, I purchased about 10 different species of conifer, such as Norway Spruce, Black Hills Spruce, Alberta Spruce, Oriental Spruce and a few species of fir, including Fraser fir. All of these were 1-3 feet in height saplings. All survived through the summer there, kept mostly shaded during the afternoon and evening, except the Fraser fir, which was dead within 3 weeks of arrival. The tree arrived in mid-April and was dead by early May.

Now that I am in PA, I have been gradually building up my collection of pre-pre-bonsai saplings to work on as bonsai in the long term. I received 3 young Fraser fir in the mail a couple days ago (all just over a foot in height and pot bound in small 2-3 inch black pots. The two in shade are fine as of this afternoon, but the one in I sat in direct sun is completely dead, even though the roots are as moist as when it arrived. Temperatures both yesterday and today peaked in the low 80s.

I conclude that for bonsai purposes (grown in a pot), Fraser fir is difficult at best in locations that ever experience hot weather, because the roots cannot get really warm/hot even for short periods.

What other trees have you all found to be intolerant of periods of warm or hot weather (either struggles or just flat out dies).
 
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#3
I would speculate that Balsam fir will also be similarly difficult as a potted tree in areas with real summer heat since it is possibly the same species as Fraser fir.
 

Smoke

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#4
I tend to do it backwards. I work with species that are heat tolerant. They need to tolerate this. Air temp today is 106. Soil temp half way down was 111 about 5 degrees hotter. This particular cork elm is in full sun all day. Grows like a weed even at this temp....as long as its watered. Trees under shade cloth are about 85 degrees.
DSC_0011.JPG
 

Paradox

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#5
I tend to do it backwards. I work with species that are heat tolerant. They need to tolerate this. Air temp today is 106. Soil temp half way down was 111 about 5 degrees hotter. This particular cork elm is in full sun all day. Grows like a weed even at this temp....as long as its watered. Trees under shade cloth are about 85 degrees.
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I wouldnt say its backwards. You are growing species that are tolerant of the conditions where you live. I call that a smart choice in species to work with.
 
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#6
Heat in daytime alone is not likely to be a problem. High night time temps are a real killer. Think about it, mountain ski buffs know even at 10,000 feet (slightly less than 3000 meters) it can be 80 F during the day. At night in high elevations the temperature quickly drops, usually more than 20 degrees F or more than 11C. The cool nights lower the metabolism, the tree then burns less energy at night. Too warm at night and the tree can not build up the energy, stored as sugars and starches it needs for growth.
 
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#9
Good points mentioned above!!

I think it is safe to say that boreal, sub arctic fir species and tamarack trees in pots might be unable to handle occasional bouts of hot weather in small pots and as such are probably best suited for zone 5 locations and below.

I suspect even the most cold loving, deciduous species from subarctic climates would fair better, trees such as Acer ginnala.
 
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#10
So, what constructive, helpful information can be taken away from this thread? Perhaps, it is to only grow the conifers from cold climates in their appropriate zones and not try to zone push farther south. Also, for those growing species like larch and fir as bonsai in appropriate zones, care should be taken to avoid prolonged excessive temperatures at the rootzone during heatwaves.

This is probably common knowledge to the folks around here, but I did want to share my experiences with Fraser fir's heat sensitivity if nothing else.
 
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#11
Something is askew here. The Fraisers native range is the southern Appalachian Mts. where it habitats rocky outcrops. It's not a preferred timber tree primarily because of its habitat. It is the number one choice for Christmas tree farmers, who grow them in plantations in full sun. It is given an intermediate tolerance to shade. Doesn't sound much of a wimpy tree in any respect.
I realize in containers some temperance is needed and adjustments made to maintain the vitality of the tree, but I have a doubt about the Fraisers succumbed to the heat alone. I would suspect a combination of factors caused the demise. Perhaps a hot pot? Add water and you've got steamed roots. Something of that sort. Most conifers will go into a semi dormancy when the temperature gets excessive. That's how they survive the heat.
 
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#12
Something is askew here. The Fraisers native range is the southern Appalachian Mts. where it habitats rocky outcrops. It's not a preferred timber tree primarily because of its habitat. It is the number one choice for Christmas tree farmers, who grow them in plantations in full sun. It is given an intermediate tolerance to shade. Doesn't sound much of a wimpy tree in any respect.
I realize in containers some temperance is needed and adjustments made to maintain the vitality of the tree, but I have a doubt about the Fraisers succumbed to the heat alone. I would suspect a combination of factors caused the demise. Perhaps a hot pot? Add water and you've got steamed roots. Something of that sort. Most conifers will go into a semi dormancy when the temperature gets excessive. That's how they survive the heat.
Cut your own tree farms have stopped planting Frazier goes around Chicago. In talking to one owner he said the trees could not handle the heat and soil types in the area, and the trees that did survive were not worth selling, as they grew poorly and had missing branches.
 
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#13
Something is askew here. The Fraisers native range is the southern Appalachian Mts. where it habitats rocky outcrops. It's not a preferred timber tree primarily because of its habitat. It is the number one choice for Christmas tree farmers, who grow them in plantations in full sun. It is given an intermediate tolerance to shade. Doesn't sound much of a wimpy tree in any respect.
I realize in containers some temperance is needed and adjustments made to maintain the vitality of the tree, but I have a doubt about the Fraisers succumbed to the heat alone. I would suspect a combination of factors caused the demise. Perhaps a hot pot? Add water and you've got steamed roots. Something of that sort. Most conifers will go into a semi dormancy when the temperature gets excessive. That's how they survive the heat.
I ran out of time for typing, I was going to add essentially what @RKatzin mentioned. To loose a tree in only 3 weeks, when all the others you listed survived says there was most likely something else going on. Heat probably did not help, but it may have been something else. It usually takes more time for heat decline to do in a tree.

Abies, firs in general, if you had to guess, usually prefer an acidic soil, much like azalea or blueberries. The soils they grow in tend to be derived from decaying forest litter & or moss & inorganic rock or gravel. They are not often found in clay soils. (there are exceptions, but in general no clay). If your mix included calcined clays, such as Turface, or gravel (or coarse sand) that included a lot of limestone, or high calcium content media, the roots may have reacted negatively to the soil pH. Or the mycorrhiza reacted negatively to the soil pH.

The low frequency of Abies in bonsai photos of show quality trees suggests their horticulture is not ''easy''. I suspect they are more toward the ''obligate'' end of the spectrum in terms of requiring mycorrhizal fungi. Some tree species, whole genera of trees survive just fine without mycorrhiza, some really require mycorrhiza to thrive. I suspect, but have no proof, that this may be the case with firs. In which case when you make up your potting mix, the organic component needs to be well composted, so that it will allow quick re-establishment of mycorrhiza, and feed the mycorrhiza. I have used fresh fir bark in my mix instead of composted bark, and have noticed a longer recovery period is needed for my spruce before the tree really gets growing as fresh bark is somewhat anti-microbial. I first explored mycorrhiza researching horticulture of terrestrial orchids. My knowledge of how mycorrhiza works with trees is not as well researched. Others feel free to correct me on my thoughts.
 
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#16
Something is askew here. The Fraisers native range is the southern Appalachian Mts. where it habitats rocky outcrops. It's not a preferred timber tree primarily because of its habitat. It is the number one choice for Christmas tree farmers, who grow them in plantations in full sun. It is given an intermediate tolerance to shade. Doesn't sound much of a wimpy tree in any respect.
I realize in containers some temperance is needed and adjustments made to maintain the vitality of the tree, but I have a doubt about the Fraisers succumbed to the heat alone. I would suspect a combination of factors caused the demise. Perhaps a hot pot? Add water and you've got steamed roots. Something of that sort. Most conifers will go into a semi dormancy when the temperature gets excessive. That's how they survive the heat.
The species may be tough in many respects, but as a tree from a boreal/taiga climate in the high elevations of the Appalacians, it is clearly not tolerant to heat and it now appears based on several bits of info on this thread, the Fraser fir is particularly intolerant of hot conditions, moreso than the many other northern boreal species that can and do thrive in the Chicago area.

Has anybody ever heard of Chicago having summers too hot for any other species of tree? I would not have believed it.

Also, I think the roots did heat up in the sun and that is a big part of the species' heat sensitivity, the roots cannot tolerate being hot.

Further, I had other very northern conifer and deciduous species in small black pots (same conditions) in full sun that 80F day and they were all fine. The Fraser fir was the only one that couldn't take it.
 
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#17
If anybody comes up with any other heat intolerant when grown in potted tree species, please post info in this thread.

I'm derailing my own thread here, but in noting the intolerance of hot conditions and the general difficulty in keeping fir species as bonsai, this got me to wondering if Abies (and actually evergreen conifers in general) are the world's most cold hardy/cold tolerant/northernmost growing trees.

After some research, the answer I came up with is, no. While several genera of (evergreen) conifers dominate many of the boreal forests of the world, areas with the most extremely cold arctic climates have few tree species and the ones that do exist are from the genera; Populus (aspen), Larix (larch) and Betula (birch). Specifically:

Populus tremuloides - hardy to USDA zone 1, range goes all the way north to northern Alaska

Larix gmelinii - native to northern Mongolia and Siberia, reputedly survives to temperatures as low as -70F

Betula nana - the range of which is described as mainly the "tundra of the arctic region" from Wiki

Betula pubescens - this birch's range extend further north into the arctic than any other broadleaf tree
 
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Bonsai Nut

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#18
I think there is a difference between "heat" intolerance and "sun" intolerance.

For example, I have some cacao trees in my backyard growing in almost complete shade. They are a temperate rain forest understory species. If they get any direct sun on their leaves, they start to brown - even when I had them sitting in my kitchen this winter. However it can be over 100 degrees (air temp) and if they are in shade they are fine.

Same thing can be said for many plants (ie not trees). For example I have ferns growing in my landscape around my koi pond in complete shade. They don't seem to care one way or other about air temp, but if I trim my palms and they get direct sun they start to stress - even in the colder winter time.
 
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#19
Abies, firs in general, if you had to guess, usually prefer an acidic soil, much like azalea or blueberries. The soils they grow in tend to be derived from decaying forest litter & or moss & inorganic rock or gravel. They are not often found in clay soils. (there are exceptions, but in general no clay). If your mix included calcined clays, such as Turface, or gravel (or coarse sand) that included a lot of limestone, or high calcium content media, the roots may have reacted negatively to the soil pH. Or the mycorrhiza reacted negatively to the soil pH.
Leo, I was confused by this paragraph. I was under the impression that turface was acidic?
 

GrimLore

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#20
I think there is a difference between "heat" intolerance and "sun" intolerance.

For example, I have some cacao trees in my backyard growing in almost complete shade. They are a temperate rain forest understory species. If they get any direct sun on their leaves, they start to brown - even when I had them sitting in my kitchen this winter. However it can be over 100 degrees (air temp) and if they are in shade they are fine.

Same thing can be said for many plants (ie not trees). For example I have ferns growing in my landscape around my koi pond in complete shade. They don't seem to care one way or other about air temp, but if I trim my palms and they get direct sun they start to stress - even in the colder winter time.
Exactly how it works here too. Even Ficus(any type) handle shade and any temperature. Put one out front for a day in Full East/West sun and they pretty much defoliate. My Wife and I have been experimenting with a lot of plants since we moved here in 2013 and it actually seems VERY FEW even if labeled Full Sun can actually handle it. Interesting thing we have found in Full Sun that Colorado Spruce, Birds Nest and other spruce do great in it as well as Cypress in the ground or potted. Also noted Holly hates it but a Foo Holly grows nicely. Fruit trees of any type do good too as well as a lot of flora(not roses). She puts out the banana tree for the Summer and it does ok and first time here a Bird of Paradise. Maples here cannot be in full sun if potted but Elms of any type grow like weeds :) As you mentioned "They are a temperate rain forest understory species." and not paying attention to a plant label but what the plant is makes all the difference.

Grimmy