Scion priming in junipers: would it work?

[Wires_Guy_wires]

One of the key reasons of failure in scion grafting, is a lacking connection between scion and receiver.

For a couple of years now, I've been fiddling with the idea to cut my scions, wrap them, and instead of inserting them in the receiver tree, first put them in the fridge in a callus-inducing medium for a week.
In theory, it should induce a healing response in the scion and thus get a stronger response from the receiving plant. The risk is that it could jumpstart growth, or inhibit growth all together.

Has anyone ever tried it? Or read about it? If so, I would like to hear your findings! Otherwise, I'll set up an experiment of 4 treated and about 6 or 8 untreated ones. But the main issue is that I haven't been able to find a solid composition for callus induction in junipers.

 

[SeanS]

This has been a point of discussion recently on the Bonsai-U platform. Bjorn posted a video last week where he documented his experimental process of using hormones while grafting a juniper.
You’d need to be a member on his platform to watch the content and see the paper.

 

[Gabler]

This has been a point of discussion recently on the Bonsai-U platform. Bjorn posted a video last week where he documented his experimental process of using hormones while grafting a juniper.
You’d need to be a member on his platform to watch the content and see the paper.

View attachment 586343

Did it work?

 

[Empty Mountain]

Maybe @Canada Bonsai can share his results with us?

 

[SeanS]

Did it work?

Results will be assessed later in the season, Bjorn only just performed the grafts

 

[Canada Bonsai]

Maybe @Canada Bonsai can share his results with us?

LOL You guys are gonna get me in trouble!

Let's pretend say I didn't see Bjorn's content, so instead I'll speak generally on the topic

Here is a paper from 1992, and a screenshot of one of the paragraphs that capture the general idea

When using IBA for grafting, you want to submerge the cut ends of your scions in the IBA-water solution, prior to grafting -- exactly as you would when performing hardwood or softwood cuttings. The concentration and length of time varies tremendously from species to species - there is no one-size-fits-all. Clonex and gel-type hormones are unlikely to work well because they disrupt cambium contact. The goal is to get the rooting hormone inside the scion, not on the scion, before grafting it. If a bonsai professional one is going to insist on using something like powder or gel, I would recommend a multi-hour or overnight dip, and then re-cut the scion prior to inserting it into the receiving plant. One benefit of using liquid hormone is that you don't necessarily need to re-cut your scion, although I would recommend doing it anyways. If your powder or gel obstructs cambium contact, you might as well just put the scion in the garbage, it is not worth your time -- at that point, you might as well just graft without hormone but with good cambium contact. Another advantage of using liquid is that you have total control over dosing, whereas trying to dilute powder or gel is a nightmare.

...as a general rule, when it comes to grafting (or propagation) there are people in the world who graft more per hour than our bonsai professionals have grafted in their entire lives... Everyone has their areas of expertise, but it is good to be curious and experiment outside of those areas, too

 

[Wood]

The goal is to get the rooting hormone inside the scion, not on the scion, before grafting it.

This is an interesting angle that I didn't quite realize from reading the abstract of the two papers and watching Bjorn's video. It intuitively makes sense that getting hormone into the scion would trigger better growth and healing

The second paper (Moghadam, Ardebili, and Rezaie) mentioned that follow-up applications of IBA to graft sites dramatically improved graft performance. The authors didn't describe how the follow-ups were applied, but Bjorn guessed painting the IBA solution onto the graft union. Any thoughts on how/why that made a difference?

 

[Wires_Guy_wires]

LOL You guys are gonna get me in trouble!

Let's pretend say I didn't see Bjorn's content, so instead I'll speak generally on the topic

Here is a paper from 1992, and a screenshot of one of the paragraphs that capture the general idea

When using IBA for grafting, you want to submerge the cut ends of your scions in the IBA-water solution, prior to grafting -- exactly as you would when performing hardwood or softwood cuttings. The concentration and length of time varies tremendously from species to species - there is no one-size-fits-all. Clonex and gel-type hormones are unlikely to work well because they disrupt cambium contact. The goal is to get the rooting hormone inside the scion, not on the scion, before grafting it. If a bonsai professional one is going to insist on using something like powder or gel, I would recommend a multi-hour or overnight dip, and then re-cut the scion prior to inserting it into the receiving plant. One benefit of using liquid hormone is that you don't necessarily need to re-cut your scion, although I would recommend doing it anyways. If your powder or gel obstructs cambium contact, you might as well just put the scion in the garbage, it is not worth your time -- at that point, you might as well just graft without hormone but with good cambium contact. Another advantage of using liquid is that you have total control over dosing, whereas trying to dilute powder or gel is a nightmare.

...as a general rule, when it comes to grafting (or propagation) there are people in the world who graft more per hour than our bonsai professionals have grafted in their entire lives... Everyone has their areas of expertise, but it is good to be curious and experiment outside of those areas, too

I have worked the fields as a teenager. I could do about 1500 grafts in a day. The Polish workers could do 1500 before lunch, if you were on the wrapping side of it, it was hard to keep up. But those were bud T-grafts on roses. They didn't need to be perfect, they just needed to be done.
I think the same goes for tree cleft grafting and the likes; they're often not as pretty.
I find quality of grafting important in bonsai.

I can get hormones into scions, no big deal. Same goes for after treatments, but my results in those were varied: most of the time there was no noticeable response.

Painting the union would not make sense to me. Because plant cells sure can take up liquids and solutes, but a healing wound usually shouldn't. And I need the wound cover to stay in place; I've ruined scions more than a lot of times by checking the wrap integrity and moving it too much. Instead, I'm thinking of using bags that I can spray inside and make use of the foliar uptake instead. Or syringe injection into the wrap, maybe. Those are easier to seal off and parafilm wraps don't flap in the wind as much as bags do.

 

[JeffS73]

Just to offer a little info if anyone is going to experiment:
IBA-K is quite readily available on ebay, and has the advantage of being water soluble, de-ionised or RO water would be best. You will need some very sensitive scales for measuring.

 

[JeffS73]

If going down the foliar route adding high purity fulvic acid and a surfactant like yucca or 'Transport' from optic foliar might help. As an aside, Transport might be fulvic acid.

 

[Wood]

Painting the union would not make sense to me. Because plant cells sure can take up liquids and solutes, but a healing wound usually shouldn't.

Agreed, but it seems like the data from the paper disagrees. Here's two graphs from it, measuring scion diameter and length





Some caveats are that the paper is about grafting cacti, not trees, but I think the same horticultural concepts are generally similar

 

[Wires_Guy_wires]

If going down the foliar route adding high purity fulvic acid and a surfactant like yucca or 'Transport' from optic foliar might help. As an aside, Transport might be fulvic acid.

Fulvic acid is a good chelator, it transports ions, rarely whole molecules. Due to it's high molecular weight and 3-dimensional size it is not the best transporter. It has magical properties we shouldn't ever dismiss, but in this case they're not the best suited.
For surfactants I'm using Tween 80. It's plant safe and doesn't have any counter indications.
IBA-K is fun, but the free floating potassium might be problematic, which is why I plan on using DMSO as a solvent for the dip; the potassium shouldn't dissolve in it and thus stay out of solution. Water solubility is great for foliar application though.
Then again, I might go for NAA or another auxin.
I've tested junipers in the past for DMSO toxicity and they seem to be unaffected.

As for cacti comparing to woody plants, it's a wildly different horticultural concept. They have different metabolisms; cacti use CAM photosynthesis and most woody plants do C3. Cacti have stomata over their whole outer layer and are prone to take up water through them when they can; in cold conditions, at night, or at high humidity. I didn't see where the images come from, but my bet is they treated at night or at lower temperatures to get maximal absorption - I managed to find the article and it's indeed 20 degrees C. The plants I graft have leaves and woody parts.. There's more to be said but let's just say I would not dare to compare the two.

Bjorn seems to aim for elongating cell growth and using IBA alone, I plan on mixing in cytokinins because in my experience the biggest issue with grafts taking is the undifferentiated cells not forming in the wound site of both the scion and the receiver.

Maybe a mix of finely ground activated charcoal suspended in glycerole + hormones, could be provide a stable release of hormones on the wound site. Those nanotubular structures have ends on both sides, so everything that is taken up, has to come out at the other end at some point. Which is why carbon filters don't last forever and should be treated as chemical waste.

Keep them coming though! We might be on to something interesting!

 

[JeffS73]

DMSO... I've considered it in the past for root hormones so that would be very interesting. If the potassium is a problem, can't you use straight IBA? As another aside, do you think the potassium in IBA-K is a problem for rooting? I've had limited success copying the dip n grow formula using IBA-K.

 

[Wires_Guy_wires]

I can use straight IBA but it's so unstable in powdered form that I would need to make aliquots and keep those frozen. I much prefer extracting it with dmso and then mixing that dmso extract with water, the end result should be purified IBA, since the K doesn't dissolve. This way I can store the powder in the fridge, which takes less space.
Since the K in IBA-K has a 1:1 ratio of K : hormone, a 100ppm solution would also contain 100ppm K. This is not a problem in low concentrations, but in higher concentrations it can change the nutrient profile and cause some deficits on the other end of the sprectrum. It shouldn't be a huge issue most of the times, but I have seen negative responses in some plants.
Alternatively IAA can be used but it's even less stable than IBA.

The drawback on dmso is that it freezes at 18°C. So I would need to apply it on a warmer day.

 

[nuttiest]

Have you noticed a difference when you cut back the tips of scion? It might help on excurrent branching types.

 

[Wires_Guy_wires]

Have you noticed a difference when you cut back the tips of scion? It might help on excurrent branching types.

I have done so, but it seems that it made no difference in the amount of takers. I still do it though, since it does seem to improve cutting strike rates.

 

[nuttiest]

I still do it though, since it does seem to improve cutting strike rates.

It does? On cuttings I leave the tip, but also don't have a high success rate with juniper cuttings. Interesting it doesn't matter on the reworking though, I need to pay attention to this thread because I don't want juniper anymore unless I get something softer. Either I sell them and keep one to rework, or just be out of it. Are most junipers compatible?

 

[Wires_Guy_wires]

Are most junipers compatible?

Sorry, I don't understand your question. Compatible for cuttings? Only communis is the odd one out and doesn't root as a cutting.
For grafting, thus far I've only grafted itoigawa, chinensis, blaauw and kishu. They take on all the junipers I've combined them with, again with communis being the odd one not accepting anything.

Needle juniper grafting requires a bag, they poke right through the parafilm wrap, leaving them somewhat unprotected.

 

[nuttiest]

For grafting, thus far I've only grafted itoigawa, chinensis, blaauw and kishu. They take on all the junipers I've combined them with, again with communis being the odd one not accepting anything.

That's what I wanted to know!