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Three-part grafts for Apples
Based on personal experience, how have 3-part grafts between rootstock, interstem, and scion worked?
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Reinettes
Lewis Co., WA
426 Posts
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1
February 14, 2024 - 7:37 pm

Dear Forum members,

I've recently been wondering about 3-part grafts of apple trees relating to a vigorous rootstock, with a dwarfing or semi-dwarfing inter-stem, used for the final intended graft.  I could be wrong, but if my memory serves, at least a couple of you have mentioned these in the past.

Needless to say, I've been thinking about the potential option in recent times.  If any of you might have had the patience to try this technique in the past, I'd like to know the outcomes of those efforts.

Dwarfing rootstocks are useful, but tend to require exquisite care and fertility because of their smaller root systems and need for support.  The rootstocks of a seedling apple or larger "semi-dwarfing" rootstock tend to be widespread and useful in providing both support and nutrients for the subsequent tree.  

Does the "great, sturdy, well-rooting rootstock" plus a dwarfing or semi-dwarfing inter-stem, plus the top-grafted intended scion result in a healthy, productive fruiting tree of reasonable merit?

...Just one of those things that I've been contemplating....

Reinettes.

[P.S. -- Jafar:  My Forum contribution is on the way, finally....]

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John S
PDX OR
2817 Posts
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February 14, 2024 - 9:45 pm

That's an interesting question.  I have grafted dwarf rootstock onto seedling trees and it hasn't worked as well as I would have thought.  Many of the top parts of the trees seem extremely stunted when I've done this.  They don't seem  to want to grow afterwards.  Maybe I should have grafted dwarf onto semidwarf rootstock.

JohN S
PDX OR

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Reinettes
Lewis Co., WA
426 Posts
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3
February 16, 2024 - 4:44 pm

John,

Thank you so much for your input on the matter.  I guess that so much of this is about trial and error.  

In a "standard, typical apple", let's say a seedling tree, there must be a balance between the root system and the top growth.  They both interact appropriately in terms of nutrients, one to the other.  Is a scion, grafted onto a dwarfing rootstock, necessarily restricted in growth by the curtailed ability of the roots to acquire the necessary nutrients to produce top growth any larger than the roots will allow?  I think so.  Dwarfing rootstocks, in order to be used successfully in grafts, need extremely fertile soil, as well as support.

I guess that what I've been wondering about is the idea of establishing a standard (or "semi-standard") rootstock for -- say 3+ years -- so that the foundation (i.e., roots) can get well-established, and then "replacing" the "top growth" with a dwarfing interstem.... such that the rootstock of established size is already in place pulling in sufficient water and fertility from the soil.  Perhaps with the larger, established, root system there might be greater vigor in what is grafted, and, thus, have greater vigor for the final, terminal graft?

🙂   ...These are just some of the things that I occasionally wonder about.  In grafting with dwarfing or semi-dwarfing rootstocks, there must always be some some form of balance between the top growth and the roots.

Reinettes.

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Rooney
Vancouver SW Washington
778 Posts
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February 16, 2024 - 5:33 pm

Your reasoning on this is totally correct Reinettes. 

I have learned things about hardiness about fruit trees through the hands of mostly NAFEX members from northern states and Canada. It's generally regarded that roots of any apple tree never stop growth the way the rest of the tree must to harden off in time for the annual freeze.

The intervals consist of (1) almost complete dormancy (except the roots), (2) active green growth, (3) ceased growth, and (4) the conversion steps into the almost completely dormant interval again without leaves.

The measure of a trees ability to dwarf is best to look at the ratio of time spent of 3 over 2. Which is applicable to anything above the roots. Now to predict how dwarfing a system is going to be without seeing the function of all these steps then the mass lengths of each portion of the tree must be taken into account and factored by the innate 3 over 2 ratio if that can be known for what ever cultivar your using. 

That said, it seems unreasonable of anyone or myself that expects a very short inter-stem of say a bud 9, that it's too short to have dwarfing effects. To which I would agree. So there must be a logarithmic equation that applies which would arrive at the correct answer. 

Besides all of this about the final product sizing, it's always been interesting what's happening during the phase-3-4 section. It's when the sugars stop providing growth to the top and use it to replace the coating of cells on everything that exists above the soil in preparation for winter. If winter happens to come before the leaves have dropped means the tree will die because the controls that decide leaf attachment know they are not done feeding the cell wall replacement process.

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Reinettes
Lewis Co., WA
426 Posts
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February 17, 2024 - 4:10 pm

Rooney,

Thank you very much for your input.  I find it very helpful and thought-provoking.  There are "Rules of Thumb", and then there is still the very real purpose of needing to experiment on one's own.  Experience with visible results under controlled circumstances is still the way to go.

No matter just how much is known, there is always so much more to be explored.

Reinettes.

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Rooney
Vancouver SW Washington
778 Posts
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February 18, 2024 - 3:08 pm

Speaking about balance that " there must always be some some form of balance between the top growth and the roots " that keeps us interested in three part grafts, via what posted 2 days earlier, this one resulted in the higher production ability by tampering with roots:

Yr-2000.png

I think this is another method besides notching (as described elsewhere) of forcing lower hanging apples that otherwise would not occur.

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John S
PDX OR
2817 Posts
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7
February 19, 2024 - 9:20 am

I have read about people using root pruning as a method of controlling size of fruit trees. I haven't really practiced it, but I know it exists as a practice.  They would just go out and chop in the soil every few years.  Keeping a plant in a pot will do the same, but you may have to repot it every so often.

John S
PDX OR

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Dannytoro1
53 Posts
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8
February 19, 2024 - 10:21 am

From what I've read; dwarfing effect of the interstock is highly dependant on length. Also like where I'm at; having a base rootstock that has great root mass helps most in sandy soils. In Poland it is not uncommon in trained and compact orchards that P.2 on B118 or B.9 on B118 are prefered for a semi dwarf habit.

Much like P.14; P.2 has a large caliper trunk per size ratio. Which helps greatly with crop loads.

Apparently 6-12" is the range of length; with 8" said to strike a balance of dwarfing and preciousness.

In non-cold areas, M111 is preferred of course.

There are a small bevy of Polish rootstocks that have not reached our continent. All are promising dwarf or semi dwarf trees.

I looked briefly at importing them through the designated channels. It seems an endeavor more suited to NASA based on the paperwork, costs and procedures.

Thoroughly Bureaucratized to futility.

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Reinettes
Lewis Co., WA
426 Posts
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9
February 23, 2024 - 5:06 pm

I can't help but laugh to myself while reading these responses.  There are just SO many variables to consider, and when my brain starts to accumulate too many numbers, ratios, and formulae it can't help but boggle!  I truly appreciate the input.  Great information to digest!

John S. -- Reading your post reminded me of the "professional" or truly traditional Bonsai tree makers, some of whom annually remove the plant from the planter in order to trim the roots in order to "check" the possible top-growth and restrict its potential....  When it comes to fruiting trees, grown for the desired fruits of reasonable size on a tree of restricted growth, I'm still left with so many ponderings.  It sounds like the kind of experimentation that requires FAR more than I'd ever be able to do in an ever shortening lifespan.

Thanks to each of you for your input!  So many factors to consider!

Danny -- When it comes the length of the interstem, I will definitely have to keep that in mind when experimenting.  It's one of those factors that I forgot about!

Reinettes.

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