Does long-term graft strength vary by graft type (when rootstock and scion are different diameter)

Sorry for the delay… we had an extended power issue.

Yes, worried about the graft union failing under snow load or strong winds… we can get both, and in abnormal times of the year. I’d probably look to others to define what the ‘at risk’ versus ‘it’s good age’, but have a number of 3rd leaf trees where the top of the scion is still not entirely healed over… I suspect something like a side graft.

I sense the type of graft will ultimately affect the strength of the union, but perhaps that wanes with age, esp. beyond 5 years.

We saw, some pretty heinous wind here this weekend… gusts in the area up to the 90’s. Sounds like once mature, there is not a strength difference for most situations unless influenced like you mention, but I wonder about our more severe events. 2 years ago, I lost (to wind) half of a 50’ pine, which had a co-dominant leader from about 15’ up… similar situation with half of a 40’ pine landing on the house a few weeks ago after 2’ of heavy snow. Of course, those are known weak situations, but my point is that wind and snow load can be the real deal here.

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Tell me more about that… I don’t think I’ve ever seen those deep versions mentioned. I would say every few years, we have some winds in the 75-90 mph range.

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This is from old village men’s and travelling grafters’ (used to be a thing in CE pre WW2) tales comparing grafting to joinery (in the fashion of stability of different approaches of attaching a leg to a chair - would you rock in one if the back legs were glued from the back side?) and some old Czech and Slovak literature where types of grafts were discussed in terms of weather conditions. Bottom line being wedge and W&T (almost forming a Z-like double wedge) are more stable. Side grafts were discouraged
& SG on the side towards which the wind blows and most trees in the area are leaning was mentioned almost like asking for it.

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Those traveling pomiculturists would graft wild seedlings and maybe see the trees in a few years, some of them in remote locations. So there was no after care expected.

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I can’t tell you more, but that rule makes sense. Some grafts will be stronger than others especially in the short run. Short run being a few years. Bark grafts of certain kinds that basically heal mostly on one side will be weak.

With 90 mph winds the best hope is a strong form of support.

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This is my first ever bark graft experiment from last year. It is Braeburn apple on M9. It is in one of the less windy spots I have and I grafted on the wind exposed side so as not to rig the experiment to an extreme. The M9 (wheelchair rootstock) was pushing it enough, but I used that because it is popular and I wanted to see, how it recovers, anyway.

And here is the other side - I grafted under left flap. I cut off the unattached bark to see the joining. Now, it was a crappy year, as in zone 5 spring and I would have grafted later, had I known… But the rootstock did not even callus.

I was planning on giving it a strong nudge next year, but I don’t think it will be necessary if there is any fruit. I might try it on a vigorously growing seedling, when I find one large enough and free, just to see if I get a better result. But I don’t see myself bark grafting any time soon, unless it is an old tree.

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To be honest, I do use side grafts (side+W&T or modified cleft depending on scion width), but only on branches for back-up / scion repository. By the time those bear more than a few kilos, I have grafted them elsewhere and can spare the branches should they come off.in a wind storm.

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So, wedge & W&T are preferred. What about when the scion and rootstock calibers are not matched?

Sorry for any confusion… that was in reference to what a deep wedge or deep w&T are.

Agreed support is a good thing. Yes, have always struggled to think of bark grafts as becoming strong, when the ratio of branch/rootstock to scion is large. Makes me think a little more about top grafting, and how/if that is the same story.

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What do you use when there is a size mismatch?

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Either this Tiny scions - #31 by Tana , or rather more like this

if the scion is very thin - this has worked even on a Conference pear in a very windy location and that crazy thing grows like magic beans and bears fruit in clusters large enough to break branches at shoulders if we don’t thin it soon enough. I also use vigorous seedling rootstock in windy locations, so the union swells with new tissue and is likely the stronger link in the chain, so to speak.
If the scion is a regular pencil size or slightly thinner, then normal wedge just aligning cambium on one side only. (pushed in so deep it would seem like no wrapping was necessary if it were not for the blasted windy weather :wink: )

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Thanks, Tana. I had a look at that goat’s foot/inlay graft, and will go look a the rest of the thread. Getting the shape of the cavity on the rootstock to match seems pretty advanced, but I will do some practice.

In my case, the rootstocks are around 6mm and some of my scions scion around 2.5-4mm.

When I was looking up wedge graft, I saw an image looking like this, which would be more simple with the 1/2-width scion inserted only on one side. Would the void left on the rootstock be a problem, provided it was coated? I would think an air gap could cause bigger issues.

My grandparents on one side of the family immigrated to the US from Slovakia, as children.

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With that size you can’t really get a significant gap. Just use a straight wedge and wrap it tight. The gap will seal itself during the season. I would rather wrap the top with tape than use any grafting paint/wax coating (if that is what you mean by coating) which could leak into the possible cavity and prevent it from filling with bark/new wood naturally.

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Ok, thanks for letting me know… good to understand about the void and back back-filling, too. Do you think for windy areas this is a better approach than the modified cleft, or they are equally good?

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I am thankful this region has no 90mph winds, nor 4 inch rains in a day. My experience thus far argues the strength of the bond between stock & scion may be more important than the graft type over time. I had Edelborsdorfer on Geneva41. In its eighth leaf a pair of 60 mile-per-hour gusts broke it off right at the graft union. Edelborsdorfer had heavy twigs & a stout trunk by then. The break was astonishing - clean as a whistle.
I had other apple trees grafted via wh-&-t, cleft, saddle & chip-bud onto EMLA26, Geneva30 & Budagovsky118. None of those showed any sign of strain in the same storm.
Commercial sites state Geneva30 doesn’t do well with Gala, which apple has light brittle wood. I would hazard Gala doesn’t do well with many stocks. I had no interest in growing Gala, so cannot comment on it directly.
Avoiding G41 & Gala, along with reasonable after care: strip precocious trees when too young to handle fruit load &/or thin heavily until you deem your tree capable of handling the load; watering deeply in dry conditions on a weekly basis so roots strike far down; pruning to get desired shape & size for carrying crops & allowing bees access to flowers, and so on, will reduce or eliminate the dangers.

That goat foot graft is interesting. I may try it this year.

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Personally, I go for wedge. It is more stable (definitely early on) even without joining or support. Things fly in the wind, animals may knock into it, too. And I’m not a gambling person (plus that joinery analogy took too well , since I studied industrial design).

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I think I’ve gotten turned around now :slight_smile: I’m still trying to learn all the different graft types! Are wedge and cleft graft the same, versus modified cleft (where it’s pushed to the edge)? I think that is what you’re saying.

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Or I’m too tired. Thanks. Fixed.

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Have a nice evening. You’ve been very helpful :slight_smile:

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