Let's talk about what to do when our plants don't pay attention to the calendar

coachspinks

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Dave asked that I start a new thread on this. Maybe we can use this as a discussion on what to do with our plants when the weather isn't following the calendar. I am in Georgia and after weeks of warm weather we finally had a couple of just barely sub freezing nights. I have several small maples, not in bonsai pots, that have unfurled their leaves. Should I repot or not? These are very small and inexpensive so the downside of a mistake isn't that bad. What if they weren't inexpensive. I have a couple more collected trees that are also showing green. I don't plan on repotting these but what if I were?
 

Dav4

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Any chance we can see some pictures of the trees in question? If the leaves are truly open, they have no frost resistance any more and have to be kept above freezing from here on out.... and re-potting now, if needed, would be the way to go. Also, where are you keeping these trees and do you have other options going forward?
 

coachspinks

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I will try to take some pictures in a while. The trees are currently in mulch in my garden. They are protected from wind and the temps there are normally a little higher than the air a few feet above. If I had to move them I would put them in my garage. Temps don't go belong 60 in my garage but there isn't a lot of light.

What is the downside of repotting now vs later if I can provide protection from freezing? If I do wait until later won't I be repotting deciduous trees when leafed out?
 

Dav4

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I will try to take some pictures in a while. The trees are currently in mulch in my garden. They are protected from wind and the temps there are normally a little higher than the air a few feet above. If I had to move them I would put them in my garage. Temps don't go belong 60 in my garage but there isn't a lot of light.

What is the downside of repotting now vs later if I can provide protection from freezing? If I do wait until later won't I be repotting deciduous trees when leafed out?
There's actually a pretty large window for re-potting maples when they've begun breaking dormancy. I've re-potted them before bud push, as the buds are beginning to swell, and when they've actually got 3-4" long extensions of new growth present. The further along into spring we are, the warmer the weather will be with stronger sun and longer days, which is exactly what we want for newly re-potted trees to have to recover from the root work. Swelling buds, in and of themselves, doesn't mean re-potting time is here, as they are still pretty freeze tolerant. Trees re-potted in cool/cold weather with relatively low light levels will sputter along for several months until spring truly arrives.
 
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I keep to the philosophy: the tree dictates its own time.
And yes, that means sometimes there are a few bad years in a row. Most of our fruit trees are adapting and using daylength as dormancy trigger instead of temperature.
Last year I did put a few closer to the house when they came out of dormancy, and it didn't help a lot.
My practices are not advisable, but they save me a tonne of worrying and backbreaking moves. If the plants want to act up, I just let them.
 

Sifu

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What a coincidence: Since yesterdday I've got a disobedient tree in my collection two :) A trunk chopped european hornbean from nearby forest, which just doesn't want to go completely dormant.
Shots and leaves on this trunk chopped tree had been eaten almost completely by deers i guess (at least one, maybe two times in 2018) and a short new ones that appeared after in the end of august are still very greenish and not hardened enough. Many buds and even some (frozen)new leaves were left opened. I digged up the tree, pruned all those semi opened buds and cut away leaves and i hope for the best.
Nothing should get wrong with repotting/transplanting in january as long as you keep your trees (roots) above freezing. So i digged up this old european hornbeam just yesterday and put the tree in unheated greenhouse.The roots will have 2 or 3 months to establish in a pot and grow a little bit before spring arrives. I am sure the tree will survive (it's a european hornbeam, very though species), it could loose some vigorous though. If i would leave the tree in the forest until spring some serious freezing could kill it or damaged it hardly ...
 

coachspinks

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At what temp do deciduous tress decide to wake up? I understand that species are different and that there even differences within species.
 

BrianBay9

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I had some trident maples, cedar elm, flowering quince that never lost their leaves. It's been a mild winter so far, even for us. It's repotting season for deciduous trees here. My approach has been to defoliate and go ahead and repot. Guess I'll see if that causes any problems.
 

0soyoung

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At what temp do deciduous tress decide to wake up? I understand that species are different and that there even differences within species.
In general, they 'wake up' when temperatures rise above 40F/5C or so.

However, many temperate species and all alpine ones have a bud chill requirement that must be satisfied first. For example, consider the case of a tree that requires 1,008 hours of accumulated chilling time. Were it in an environment where the temperatures stayed below 40F/5C continuously, buds would break as soon as the temperature rises above 40F/5C. Nothing happens if at some time before that the trees were taken out of cold storage, say, and exposed to temperatures above 40F/5C. On the other hand if the trees stay cold for 6 weeks and then experiences a 'thaw' for a few weeks before a last cold snap happens, your trees 'didin't pay attention to the calendar' - they broke bud, leafed out and got severely frostbitten; possibly killed.

Suppose one lives in a climate where the winter temperature drops below 40F/5C only overnight so that only 8 hours of chilling occurs each day, on average. It will then take three times as many calendar days, 18 weeks or 3.5 months, to accumulate the chilling hours and only after those 3.5 months will buds will break.

Then, of course, one may be in a climate that doesn't produce the required chilling time. As the temperatures warm and daylight hours lengthen, some buds may break, but growth will be weak and the tree will loose vigor and ultimately dies within a few similar seasons.

Chilling hours are well known only for a few important lumbering species such as Douglas fir that requires at least 1750 chilling hours. I have several and live in a Douglas fir forest. I have many Japanese maples; they appear to have a chilling time requirement short of 1,000 hours. Indeed this varies by cultivar. A.p. "Orange Dream" is always the first to leaf out in my collection; a.p. "Higasayama" is later. I have many, some deciduous and some evergreen that all appear to have different vernalization requirements before they bloom. I also have 'early blooming' azaleas that don't require much, if any, vernalization and they are blooming now, right on schedule. Since these are evergreens and not very frost hardy, I believe that they sense the passage of the winter solstice like tropical trees do. That would mean they really are calendar readers, but I'm guessing now.
 
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Never heard of chilling hours before. Interesting. Is there resources on known times for this?
 

Smoke

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....I wonder if plants stress out when a woman goes into labor prematurely?
 

0soyoung

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Never heard of chilling hours before. Interesting. Is there resources on known times for this?
I haven't found one as a reference tabulation.
It appears that people didn't think much about it until Waerhauser experienced a colossal failure of a Douglas fir plantation in Monterey, CA (see/Google "Failure of Grafted Douglas-Fir Planted at Monterey, Calif.", "Modeling the Effects of Winter Environment on Dormancy Release of Douglas-fir" to start). It is being more closely scrutinized in forestry research now. I occasionally spend a few weeks Googling (usually Google Scholar) and perusing papers that aren't behind a paywall. But for me it came down to finding a tidbit on one species I have, watching how it and other species I have behave while keeping track of the accumulation of chilling hours though the winter. I got lazy though and left it as a non-quantitative exercise that tuned me into how my 55 species in almost 100 varieties deal with my winters. So I am no real help - just a trouble maker.

Of course, one could buy a bunch of seedlings put them in plastic bags with damp paper/sphagnum, say, and periodically remove them from your refrigerator for a few days to see if they break bud (put them back and repeat until they do). Count the hours days in the frig until they break bud = chilling time requirement. It is how the professional researchers do it (college research assistants, for the most part). It is similar to what amateur seed growing enthusiasts do with seeds (i.e., stratification).
 
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Cadillactaste

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I lost my weeping redbud in the landscape over our wacky winter last year. The local nursery lost many trees as well. We can't do a darn thing about it...just keep chugging along. Hope we end up seeing some winter so they can have a longer dormancy. We all know a tree kept indoors without a dormancy period weakens.
 

coachspinks

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The long term forecast for the metro Atlanta area shows overnight temps near 20 for 2 straight nights early next week. As Dav said, winter isn't over yet.
 

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