Cold or warm weather post graft?

Arlithrien

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tl:dr: grafted a vine maple to a jmaple rootstock in 85 degree weather. Is the graft more likely to succeed in the current warm weather or put it into the fridge now to force it into dormancy?

I'm in a kind of unusual situation. I own an Acer Circinatum (grafted onto a palmatum rootstock) but live in Florida 9B. I will need to put it in the fridge to simulate dormancy for the winter but first I need to reduce its height so it will fit. I have done that and decided to graft the top back onto the plants jmaple rootstock. But is it better to let the graft heal in warmer temperatures or colder? Not sure if it being dormant matters if I did the graft before it was dormant.
 

Arlithrien

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Yeah I figured that much out. But I'm kind of doing it backwards and I wonder how damaging it is to do it this way. I suppose better questions to ask would be how long until a tree goes dormant after being exposed to chilling temperatures? Does a tree still heal wounds while dormant?
 

0soyoung

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"Healing" is a biological process that proceeds more rapidly in warm temperatures than cold. Cold (<40F/5C) simply equals stasis.

I cannot tell you why, as I don't understand why, but veteran grafters say not to let a newly place graft freeze.

Lastly, I've been messing with maple grafting in the summer, right around the time of the summer solstice. The cambium is thick and the bark is easily lifted to place a bud or scion under. Callus forms within 2 weeks then. However, cambium growth rate continually slows after the summer solstice, regardless of temperature, and is essentially zero in dormancy.

So, @Arlithrien, I suggest you just handle the tree just as you would had it not been just grafted and just bear in mind that it may not actually take until next spring. I can see no way that being dormant is of any help. Dormancy is a thing with pine grafting having to do with the effects of resin bleed interfering with forming the union of the two cambiums
 

Dav4

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Yeah I figured that much out. But I'm kind of doing it backwards and I wonder how damaging it is to do it this way. I suppose better questions to ask would be how long until a tree goes dormant after being exposed to chilling temperatures? Does a tree still heal wounds while dormant?
Dormancy is brought on mainly be shortening day length as opposed to ambient temperatures, and as Oso pointed out, dormancy is equivalent to metabolic stasis which means little to no healing until dormancy ends, which shouldn’t be too long in your climate....


Holy run on sentence, Batman!
 

Arlithrien

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I guess my challenge will be trying to keep the scion from drying out for the next 2 months then
 

0soyoung

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I guess my challenge will be trying to keep the scion from drying out for the next 2 months then
I would defoliate it AND humidity tent the scion in some fashion. I defoliate maple scions and wrap them in parafilm before insertion. Some people bag instead of wrapping with parafilm. I think this may be important because moisture can be lost thru the lenticels along the stem(s). I've had nothing but trouble trying to bag/wrap stems with leaves even though it might be horticulturally advantageous to keep them. It seems that defoliation is the norm and that the scion leafing out is the definitive sign of a successful graft.
 

Arlithrien

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I would defoliate it AND humidity tent the scion in some fashion. I defoliate maple scions and wrap them in parafilm before insertion. Some people bag instead of wrapping with parafilm. I think this may be important because moisture can be lost thru the lenticels along the stem(s). I've had nothing but trouble trying to bag/wrap stems with leaves even though it might be horticulturally advantageous to keep them. It seems that defoliation is the norm and that the scion leafing out is the definitive sign of a successful graft.
When I got it, it had very few leaves which were in bad shape so I ended up defoliating them anyway. It had many healthy buds though and eventually one opened and out came about 5 leaves In a row. I removed that branch at the same time as the graft scion, and am trying to propagate it as a cutting. Many of the other buds swelled too but haven't opened. It would be a waste for them to open this late in the year which is why I'm chilling it sooner than later so they're ready to pop in the spring. I did bag the scion but I'm not sure if the bag needs to be longer or not.
 

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sorce

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Sounds like you're better off Not fridging it this year.

Sorce
 

Wires_Guy_wires

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I cannot tell you why, as I don't understand why, but veteran grafters say not to let a newly place graft freeze.
Fresh grafts are in a stage where survival has the highest priority. This means they start restoring damaged tissue first, using up all carbohydrates that prevent freezing to some point. Since it's cold, there's not much photosynthetic yield and a net negative production. This also means that there's less cryoprotectant compound production; the building blocks are used elsewhere and they're scarce as long as there isn't a connected supportive system. This means ice crystals can form, and those will leak out at the site with the least resistance: the wound site. Water expands when frozen, so it'll push the wound open if ice can form. Most plants produce carbohydrate mixtures (xylitol in birch for instance, used as a sweetener) or even (poly)glycerides to prevent ice formation, but they only do so with the right triggers.

On top of that, most plants respond to this kind of stress/damage by expressing growth hormones, and most of those are dormancy breakers by default. Since the receiving plant is not exchanging hormones, carbohydrates and nutrients at full level, the graft isn't affected a whole lot by the receivers signals and follows its own rules.
It's a combination of priority for restoration, lack of building blocks to do multiple things at once, and scrambled signalling between the donor and the receiver that kill most frozen grafts.

That's the least scientific way I can put it.
 

0soyoung

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Thanks, @Wires_Guy_wires, but the simple act of cutting/slicing causes growth to initiate? Pruning in winter has no such effect.
Ordinary tissues will develop some degree of cold hardiness when exposed to a sequence of deepening chills as normally occur in fall. Why would a new graft not do likewise?

Apparently (to me) there is something in the nature of damage response that leads to a new graft being inherently unable to develop hardiness just as the growth from a newly pruned root apparently is unable to develop hardiness as can the new growth on an 'untouched' root.

But, otherwise, thanks for your intelligible explanation.
 

River's Edge

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Perhaps it would be in order to skip one year of dormancy, or delay it and allow the graft to heal first. In your climate this is possible as you are forcing dormancy in a warm climate!
 

Wires_Guy_wires

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Thanks, @Wires_Guy_wires, but the simple act of cutting/slicing causes growth to initiate? Pruning in winter has no such effect.
Ordinary tissues will develop some degree of cold hardiness when exposed to a sequence of deepening chills as normally occur in fall. Why would a new graft not do likewise?

Apparently (to me) there is something in the nature of damage response that leads to a new graft being inherently unable to develop hardiness just as the growth from a newly pruned root apparently is unable to develop hardiness as can the new growth on an 'untouched' root.

But, otherwise, thanks for your intelligible explanation.
When you prune, hard or soft, you keep most of the messaging system intact, except in the parts that you've cut off. Think of it as an ant colony; if you remove a few, the colony is going to act the same. If you cut the colony in half, it's going to act more or less the same. Pick twenty ants from a colony, and they'll not behave as a colony.. until they've found a queen and have the ability to function as a colony again. The - so to speak - governing body of a plant decides where it's going. If a cutting or graft is not connected to that body entirely, it might behave different. Plant messaging, just like animal messaging, relies on feedback loops. If there's nothing talking back, either because it's not connected or because it's dormant, then there's no loop. Well, actually there is, but it's limited to the scion itself.

Not all plants do this to a similar extent. I own a mugo pine that I've tortured over a year ago, and it flushes continuously, even throughout winter. To my knowledge junipers for instance don't give a hoot if there's a governing body or not. But in deciduous plants, it's seems to be more or less a ground rule that if the arms aren't attached to the spine, they don't function. I think the reason to those differences are found, at least for a little, in the fact that most deciduous plants have a harder time compartmentalizing their body and thus having a harder time to created their own fully functioning feedback loops.

I think bleeding is one thing to keep in mind as well. Plant tissue can expand and retract (is that the right word?) to some extent. But in fresh growth, there's usually so much water that the expansion limit is exceeded with just a few degrees below zero. Fruits, being both high in sugars but also very high in water content, turn to slush after you've frozen them. It's not because they're not hardy, it's just that the water itself expands more than the cells can take.
In damaged parts, expanding water (due to lower temps) can expel itself through the vascular system. If water can escape freely, there's no need - or possibility - for expansion. A damaged carrot will dry out faster in the fridge compared to an intact one. But both are dormant and both have the frost-protective materials flowing inside them. They're both perfectly hardy, but since they're stationary, the damaged one doesn't heal either; it continues bleeding either until the wound has dried up and closed itself, or until growth resumes and fixes the place up.

Am I still making sense? It's been a long day today. Sorry for that.
 

Arlithrien

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3 week update. Took off the cling wrap and find two or three off-white nodes growing outwards. Is this a sign of a Graft taking or failing? I'm worried they're roots but a little doubtful that roots would sprout in loosely applied cling wrap so easily.
 

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Arlithrien

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Update: When I saw my plant had sprouted "roots" at the top, I knew it was just normal growth. Removed the toilet paper roll and what we have looks pretty good.

I'm hoping this is a sign of successful graft.

Unrelated but I had a bad case of fungus gnats living in the mulch so I covered it with a layer of diatomaceous earth.
 

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