Rethinking winter light requirements for evergreens

LittleDingus

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Photosynthesis (well, the dark reaction anyway) is temperature dependent. Above ~95F some of the required enzymes denature and energy conversion basically stops. Below ~45F there reaction also slows to a crawl with very little energy converted.

Knowing this, I don't care about access to light at all for my colder tolerant evergreens. When the temps are below 40F I don't care if they are buried in snow, tucked away in a dark garage, whatever...they aren't converting energy.

But does anyone have any practical experience with species like cork oak or any of the other live oaks? Last year I stored them in the garage where they spent most of the winter somewhere between 35F and 55F. I did keep them in a grow tent with lights...but now I'm rethinking the lights. I'm actually rethinking it for my coast redwoods for the same reasons.

Is there a value to providing light to evergreens that are below 55F? Has anyone stored an evergreen in the garage or someplace where they are well above freezing but have no source of light? Note that some energy conversion can happen at 55F...but do dormant evergreens make use of it?

Last year, the lights did burn out the chlorophyll on one of my coast redwoods very early on. It sat brown all winter until the temps warmed enough to wake it up. Then it greened right up. It's browning already this year so I'm thinking it's genetic with that guy. I don't see how it does much with light during the winter. Unfortunately, the garage warms enough to wake the trees a few weeks before it is safe to move them outside, but that's a different problem ;)

Here's how I have my garage set up this winter:

20201022_162359.jpg

Nice and pink! The lights are hung to the side and angled to the wall to light up more of the trees and to keep them from shining in my eyes when I park!

There are 5 coastal redwoods and about 2 dozen live oak (suber and virginiana) on and under that shelf. The top 2 lights are pretty strong. I have 2 similar lights but half the output that I was thinking to set up for the bottom trees. But now I'm wondering if I should even bother with the top ones...

One the one hand, I trust the science :) On the other hand, I'm not sure what benefits light might provide beyond photosynthesis that would cause issues were I not to provide it? That's also a lot of trees to kill all at once ;)

Probably I should just play it safe again and hang the other lights for the oaks. I could move a few sacrificial "volunteers" to a darker area of the garage to see what happens so I can plan better next year...

Well, internet, thanks for listening! I am curious if anyone has thoughts on the necessity of light below 55F for evergreens while the trees are dormant. I'd be especially interested in any practical experience people may have on storing species like cork oak in a dark room while dormant.
 

0soyoung

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Like you, I'm not sure that it is,

PSII keeps doing its thing of reducing water according only to the rate of incoming photons. So pH in the thylakoids will skyrocket (ATP synthase isn't spinning much) and that doesn't count all the free/reactive oxygen.

Many species bump up anthocyanins which shade the photocenters (reduce the rate of incoming photons) and others, maybe more commonly bump up the xanthophylls (divert photo energy away from the photocenters into heat instead) which makes the foliage tinge yellow instead of red.

IOW, tree leaves are equipped with means of coping with being in sunlight in cold temperatures. I would think it important to provide light when temperatures rise, but when sub-55F/40F, it isn't at all clear that any light is needed. Metabolic processes are at a standstill, in essence.

Yours truly,
internet
 

Vance Wood

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I don't particularly mean to be snarky but, the questions begs itself; how many bonsai do you have and for how long and under what conditions?
 

LittleDingus

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I don't particularly mean to be snarky but, the questions begs itself; how many bonsai do you have and for how long and under what conditions?

At last count, I have nearly 200 trees. Add in orchids and other plants and that number is probably north of 400 plants growing in something other than the ground. Some I've had for decades...those are mostly tropicals that winter indoors and hardy to my zone species that winter outdoors: ficus, citrus, cherry, dawn redwood/bald cypress, sequoia, maples, elm, oaks, willows, hollies...

The past 5 years or so I've gotten more into non-native non-tropical species that need special care in my zone...some of those are what prompted this thread. Specifically coastal redwood, cork oak and southern live oak. But also some off the beaten path things like baobabs and rainbow eucalyptus.

Most of these trees will never be "bonsai". I don't care. many of them would be considered "bonsai" by most lay people but not you pros. Others are in various stages of growing out to eventually be put into bonsai pots in my lax approach to "bonsai".

I'm not sure the point of your question?? How does what I have asked beg the question of how many bonsai I have for how long and under what conditions "beg itself"?

Are you calling out that I'm somehow not doing "real" bonsai? That's probably a little unfair but I'll grant it given this is a bonsai site and there are many here well above any level I aspire to. I can live with that. I like my trees in pots....I'm not going to lose any sleep if others don't. If you feel I'm not doing "real bonsai" don't respond. Or politely ask me not post non-bonsai crap. I promise I won't get offended.

Are you somehow insinuating that I am a noob asking stupid questions and wasting everyone's time? I can assure you that is NOT the case. I've been growing things for over 30 years...orchids, succulents, trees...some of them rather unusual and challenging. A very significant fraction from seed...I've even started orchid from seed. Just because my fake internet points are low doesn't make me inexperienced. Believe me or don't. I've provided all the justification of my capabilities that I care to for this conversation.

Are you politely criticizing my understanding of plant physiology? I willfully admit I know just enough plant physiology to appear stupid...forgive me...I was trained as a physicist ;) I did have to memorize the Krebs cycle in high school though...so there's that. Besides...if I knew all the answers I wouldn't need the internet :)

So yeah, I did mean to be a little snarky...but all in fun :D It's all good. I'll take no offense at your question as long as you take no offense at my response! I honestly don't know the why my history would have any bearing on the topic.
 

Paradox

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Ive kept pines and junipers in a garage with one small window on the opposite side of the garage.
I have also kept pines and junpiers in a cold frame, on the north side of my house, sometimes covered with plywood for weeks.
The trees are dormant, they are not growing so they dont need light.
 

Flowerhouse

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I am appreciating this discussion because, yeah, it's that time of the year. My trees in pots are all heeled in on the north side of my house, mulched, with a deer fence around them. I'll add some wind protection when winter begins in earnest. I've worried that they won't get any direct sun for many months, but that doesn't seem to be a legit worry.
 

Colorado

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How many of us have picked up a pot in late fall/winter/early spring - while the tree appears “dormant - only to find new roots growing out the bottom of the container?

Sure, metabolism slows significantly in the winter, but I believe there is plenty of evidence that trees do continue to metabolize while “dormant.” I try to avoid putting my trees in complete darkness. It also just doesn’t make sense to me from a common-sense perspective.

That said, darkness is preferable to death from too-severe winter conditions. :) I do keep more sensitive trees in the garage which does have a window, but certainly much lower light than outdoors.

I don’t think darkness is likely to be fatal for many (if any trees), but I do think the evidence shows that trees will be healthier in the spring if they’ve had access to proper light over the winter. Ryan Neil talked extensively about this in a recent Mirai stream. I tend to trust his horticultural knowledge.
 

sorce

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The trees may not need light, but they are just learning of the microbial life that may, the same life that gives our trees life.

I would go to a pet store every day when I worked at Walgreens, it was right down the block, my friend talked about living in a closet when talking about insufficient space for large reptiles. That same concept applies to trees, wether we know everything that goes on with them or not. It's the or not that's likely true.

The buck doesn't stop at "do trees need light?".

@LittleDingus , love ya, but orchids don't need this consideration. Vance just means, save your time and effort!

He who lives an entire life in a swimming pool, underwater, should feel free to "garage" trees.

I'm highly antiga. Anti-garage!

Until trees use petrol, outside is their "happy place"!

@penumbra regardless of need for the tree.

If people store all their trees on the garage, where do they store their fungicides?

Sorce
 

Bonsai Nut

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Great questions and I am having a hard time answering them... because I keep finding "it depends" answers. Many of the scientific articles I am reading are focused on cash crops like grains. In general, the enzyme activity associated with photosynthesis is slow from 32 to 50 F, most active from 50 - 68 F, and slows again as temps increase above that level. At 104, the activity more or less stops. However there are many plants that have adapted to extreme temperatures - both on the high end and low end of the temperature gradient.

I am going to suggest that perhaps we focus this thread around the question of evergreens - and perhaps even broad leaf evergreens like live oaks and cork oaks. I honestly don't know the answer because these trees have evolved to take mild freezes - but usually have day-time temps above freezing, or else they experience cold spells followed by days of mild temps. My guess (based on nothing other than observation) is that these trees never go fully dormant in the way that deciduous trees do, and that keeping them in total darkness while they aren't dormant would have a detrimental effect. However I can't find anything to back up my thinking.

The best article I found specifically about cork oak indicated that they are photosynthetically both drought and heat tolerant, but did not differ significantly versus other deciduous trees at lower temps (when those other deciduous trees were not dormant). But it did not address the question of photosynthesis at lower temperatures except to note that it occurred. Nor did it answer the question of "can you keep these trees in darkness in above freezing temperatures?".
 
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JudyB

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I don't really have any scientific evidence to back up this thought, but I feel like there is a big difference between 40º dormancy and below and 55º dormancy. I feel perfectly safe overwintering any tree below 40 in pitch black conditions. (and that's the best way to keep the temps that low if you protect them as sun = heat) but I don't think that at 45-55 the tree is dormant enough to not need light. My 2 pennies.
 

JonW

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I agree, I also find unclear information about this. What seems clear is that most evergreen trees will survive winter "dormancy" (or levels of very low metabolic activity when temps are below 45f) in complete dark year after year because there are people here who attest to that. What is less clear is how much benefit there would be to providing some light, and if it is worth overwintering with access to light (if it were as easy as overwintering without light, we wouldn't see these conversations, people would just do it). Some sources, such as Ryan Neil on Bonsai Marai, say that there are clear measurable benefits to access to light overwinter. My guess about the reason for this is that winter is long - even if metabolism is at a crawl, what is the cumulative benefit of that trickle of photosynthates? As someone mentioned, root growth continues overwinter, at least in fall and spring, when temps are around 50 in the pot. In fact, many overwintering situations that keep the top of the tree relatively dormant (below 45) still allow for the roots protected by the pot and possibly mulch or cloth wrapping etc. to be over 50-degrees and growing. If growing, using/depleting photosynthates. This is the main argument for fall repoting: the is a flurry of root activity during "dormancy." These are just half-baked thoughts...

I've been asking the same question because I've been transitioning from mostly tropical trees to mostly cold hardy trees and I keep changing my mind about how I will overwinter plants like boxwood, lonicera nitida, cotoneaster, azalea... I find myself shying away from those because if I want them to have light, they need to be in my garage, and if I (or someone else) forgets to close the garage door on a cold night, some of them could be goners I presume. And you can sure that the garage door will be left open sometime in the course of my bonsai hobby.

I think there is a law of diminishing returns to consider. Adding 50% to effort the first time maybe adds 50% to outcomes. Adding another 50% to effort maybe adds 25% to outcome. And so on, each time you add the same amount of effort, the outcome is more nuanced and may only be worth it to professionals/experts. Adding light during winter probably adds a percentage to the health and quality of our trees, though we can't quantify that amount and consequently it is hard to determine if it is worth the extra effort.
 

LittleDingus

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@LittleDingus , love ya, but orchids don't need this consideration. Vance just means, save your time and effort!

I really enjoy your posts @sorce...they're like cryptic little brain teasers I just have to solve ;) But sometimes I need the answer key :(

Save my time and effort from what exactly? I suspect what people really want to say is "Don't grow coastal rainforest trees in the middle of the midwest you dumb ass!" or maybe "You're 3 zones north of a picnic...enjoy the ants?"

I give up...I need the answer key for this one...

If people store all their trees on the garage, where do they store their fungicides?

I don't have any fungicides to store ;)

Yes, I know I an dealing with trees outside their natural climate. Outside is not an option for some of them. Outside is a perfectly fine place for all the trees that I have that can handle this zone. But, yes, heresy be damned, I grow trees...and many plants...that can't survive this zone. I know the challenges. Do I fail? Sometimes. My money, my time, my fools errand...I'm not forcing anyone to participate.
 

LittleDingus

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Great questions and I am having a hard time answering them... because I keep finding "it depends" answers. Many of the scientific articles I am reading are focused on cash crops like grains. In general, the enzyme activity associated with photosynthesis is slow from 32 to 50 F, most active from 50 - 68 F, and slows again as temps increase above that level. At 104, the activity more or less stops. However there are many plants that have adapted to extreme temperatures - both on the high end and low end of the temperature gradient.

I am going to suggest that perhaps we focus this thread around the question of evergreens - and perhaps even broad leaf evergreens like live oaks and cork oaks. I honestly don't know the answer because these trees have evolved to take mild freezes - but usually have day-time temps above freezing, or else they experience cold spells followed by days of mild temps. My guess (based on nothing other than observation) is that these trees never go fully dormant in the way that deciduous trees do, and that keeping them in total darkness while they aren't dormant would have a detrimental effect. However I can't find anything to back up my thinking.

The best article I found specifically about cork oak indicated that they are photosynthetically both drought and heat tolerant, but did not differ significantly versus other deciduous trees at lower temps (when those other deciduous trees were not dormant). But it did not address the question of photosynthesis at lower temperatures except to note that it occurred. Nor did it answer the question of "can you keep these trees in darkness in above freezing temperatures?".

I think about dormancy as a cycle...and maybe you're right and broad leaf evergreens like live oaks blur those lines. For many deciduous trees, there is a pre-dormant phase where the tree prepares for dormancy...raises dissolved sugars in the sap so the sap can survive being "supercooled" or moves water out of the cells into the intercellular spaces to avoid the cells bursting during a freeze, etc...

Then the tree goes dormant. Short periods of warm during dormancy don't necessarily wake the tree up. There typically needs to be some prolonged "post dormancy" phase to actually trigger the tree to break dormancy.

Maybe the live oaks blur those lines and never truly go dormant like you've suggested? I don't know.

I know truly cold dormant species don't really need light...in fact, as @0soyoung says, many of them try to protect themselves from it!

These sort of intermediary cold species I would expect to be very susceptible to sun burn after prolonged dark...I somehow manage to sunburn my saguaro every year even though its a desert plant and I keep it all winter in the brightest spot in the house.

So I guess maybe the question is if these intermediate cold species enter a true dormancy cycle...in which case I doubt they require any significant light during dormancy...or if they just do things like thicken up their sap so it can "supercool" but otherwise try to create and store as much energy as they can.

They mustn't go so far as to evacuate water from cells otherwise they should be able to handle deeper freezes like the more cold hardy species can.

...again, I'm just slinging thoughts at the internet to see what comes back. Sort of like Rubber Duck Debugging


or back when I used to work at a laboratory and the scientists would spin up chatbot to talk to when they were thinking through a problem...
 

LanceMac10

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The trees may not need light, but they are just learning of the microbial life that may, the same life that gives our trees life.

I would go to a pet store every day when I worked at Walgreens, it was right down the block, my friend talked about living in a closet when talking about insufficient space for large reptiles. That same concept applies to trees, wether we know everything that goes on with them or not. It's the or not that's likely true.

The buck doesn't stop at "do trees need light?".

@LittleDingus , love ya, but orchids don't need this consideration. Vance just means, save your time and effort!

He who lives an entire life in a swimming pool, underwater, should feel free to "garage" trees.

I'm highly antiga. Anti-garage!

Until trees use petrol, outside is their "happy place"!

@penumbra regardless of need for the tree.

If people store all their trees on the garage, where do they store their fungicides?

Sorce



gay-rahj for about 8 years......by current law, you can't hate on a gay-rahj son..... 🥳 🥳 🥳 🥳 🥳
DSC00680.JPG
 

sorce

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Save my time and effort from what exactly?

Your time and effort😉!

I personally think it causes more harm than good, but I also understand the garage as a place some folks need a good reason to dwell in so....I can't hate!

gay-rahj for about 8 years......by current law, you can't hate on a gay-rahj son..
The before pic 😂.
walter-pall-maple-2009-04.jpg

Sorce
 

Vance Wood

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At last count, I have nearly 200 trees. Add in orchids and other plants and that number is probably north of 400 plants growing in something other than the ground. Some I've had for decades...those are mostly tropicals that winter indoors and hardy to my zone species that winter outdoors: ficus, citrus, cherry, dawn redwood/bald cypress, sequoia, maples, elm, oaks, willows, hollies...

The past 5 years or so I've gotten more into non-native non-tropical species that need special care in my zone...some of those are what prompted this thread. Specifically coastal redwood, cork oak and southern live oak. But also some off the beaten path things like baobabs and rainbow eucalyptus.

Most of these trees will never be "bonsai". I don't care. many of them would be considered "bonsai" by most lay people but not you pros. Others are in various stages of growing out to eventually be put into bonsai pots in my lax approach to "bonsai".

I'm not sure the point of your question?? How does what I have asked beg the question of how many bonsai I have for how long and under what conditions "beg itself"?

Are you calling out that I'm somehow not doing "real" bonsai? That's probably a little unfair but I'll grant it given this is a bonsai site and there are many here well above any level I aspire to. I can live with that. I like my trees in pots....I'm not going to lose any sleep if others don't. If you feel I'm not doing "real bonsai" don't respond. Or politely ask me not post non-bonsai crap. I promise I won't get offended.

Are you somehow insinuating that I am a noob asking stupid questions and wasting everyone's time? I can assure you that is NOT the case. I've been growing things for over 30 years...orchids, succulents, trees...some of them rather unusual and challenging. A very significant fraction from seed...I've even started orchid from seed. Just because my fake internet points are low doesn't make me inexperienced. Believe me or don't. I've provided all the justification of my capabilities that I care to for this conversation.

Are you politely criticizing my understanding of plant physiology? I willfully admit I know just enough plant physiology to appear stupid...forgive me...I was trained as a physicist ;) I did have to memorize the Krebs cycle in high school though...so there's that. Besides...if I knew all the answers I wouldn't need the internet :)

So yeah, I did mean to be a little snarky...but all in fun :D It's all good. I'll take no offense at your question as long as you take no offense at my response! I honestly don't know the why my history would have any bearing on the topic.
I noticed your lack of posts so I was trying to determine the quality and length of your bonsai experience. Growing bonsai is not like growing the kind of things others are prone to put into conatiners.
Your time and effort😉!

I personally think it causes more harm than good, but I also understand the garage as a place some folks need a good reason to dwell in so....I can't hate!


The before pic 😂.
View attachment 336197

Sorce
Come on Sorce; I'm not trying to gass light you but, are you trying to tell me this is your Maple????
 

sorce

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I noticed your lack of posts so I was trying to determine the quality and length of your bonsai experience. Growing bonsai is not like growing the kind of things others are prone to put into conatiners.

Come on Sorce; I'm not trying to gass light you but, are you trying to tell me this is your Maple????

No that's what Lance's looked like before 8 years in the garage!

Sorce
 
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