Thread Grafting...it's time.

John Dixon

About a week ago, I was re-potting some maples and hornbeams (it's time here in NC), and decided to do a couple of thread grafts. it occurred to me that this is an issue that many have no knowledge of, but a wonderful technique to produce a branch where one does not initially exist.

Thread grafting involves using a branch from the subject tree (or in some cases, another one that will have to be kept in close proximity throughout the process) and basically 'threading' it through the trunk. First, you must do this when the buds are NOT swollen. You want the branch to be as close in diameter to the hole you are about to drill as is possible. Make sure the branch (in most cases, really a leader) is long enough and supple enough to be useful. Determine the position where you want the new branch to be and drill a hole thorugh the trunk that will allow the branch to grow OUT into that position FROM the present location. I recommend keeping the angle as shallow as possible. This increases the amount of cambium in contact with the branch (it is not necessary though, and you can drill straight through if that is your only option). Run the branch through the hole and, if at all possible, make it snug in the hole (this is accomplished by good judgement in the diameter drill bit you use). Now seal both openings where the branch enters/exits the trunk. I personally use lac balsam most of the time, but that's your choice. The one caveat is to only "seal" the opening, do NOT force the sealant INTO the hole. The success of the graft depends on the union of the branch (scion) with the cambium of the trunk. Excess sealant may prohibit this. Now you wait.

The key to this technique is to be patient. It's usually accomplished in one season, but waiting two seasons is a good idea. The sign to look for is when the "exit" side of the branch (this is the side where you want the new branch) swells to a diameter greater than that where it ENTERS the trunk. When this is very obvious you can consider severing the branch at the point of entry into the trunk (this is common sense). If the graft was successful, it will not suffer any setback. If not, it will die quickly.

Beginners take heed. This technique has a very high level of success, probably the highest of all grafts, with approach grafting coming in next. It is not difficult, and while I understand how some consider boring a hole into a trunk as dangerous, it really isn't. Remember, the "living area" of a trunk is very small, the "heartwood" is basically support material.

Pictures tell this story well. I'm attaching a few photos to illustrate this technique. I did these on a korean hornbeam that had no branch in a critical area, and other techniques didn't work. In one photo you will see a rather liberal amount of sealant. The amount above the thread graft is sealing a wound from a failed bud graft union I attempted last year. The buds on the branch are swelling now, but at the time of the graft, they were barely visible. That's important. The last week has been unseasonably warm, and the buds are accelerating rapidly. If you wait too long, the buds will hamper your efforts.. One photo is of the subject tree last fall, and the one showing the other trees is to illustrate the point of dormancy we have now (prime time for a thread graft), which is probably 3-4 weeks ahead of colder climates.

I hope this information is useful.

John

Attached Images

	hornbeam US oct 04.jpg (22.1 KB, 134 views)
	Thread graft horrnbeam.jpg (20.2 KB, 157 views)
	Close up of both.jpg (26.7 KB, 138 views)
	re-pots 2-05.jpg (41.0 KB, 127 views)
	Close.jpg (57.4 KB, 158 views)

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John Dixon

Si vis pacem parabellum

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Ralph

Those are very small branches. Does branch size matter when performing this technique? I assume that I could take young seedlings that are still in their pot, and utilize them for the branches, is this correct?

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John Dixon

Ralph,

I PREFER small branch diameter. Someone else would have to remark about the success of larger branches, say in excess of 1/4". but up to that level I have had excellent success. You can use longer shoots, but I purposely grew these shoots for those grafts. When they are removed, the energy will be re-focused to the existing branch where the shoot has "suckered" from. I like to do that, so I stick with it. the fact that the shoot is short from the graft junction is not an issue to me. I feel diameter is much more important than length. In fact, I am trying to determine if smaller diameter shoots are the better choice. I base this on the fact that the smaller hole/shoot ratio can accelerate the grafting process. What I mean by that is the swelling, by percentage, is greater on small diameter than larger (1/8" diameter that grows 1/8" in one year is 100% bigger. 1/4" that grows the same 1/8" in one year is only 50% bigger). I am not fully convinced of that theory, so I am in the experimentation stage. I do tend to think it is sound, however. That's the premise, be it right or wrong, only time will tell.

It isn't a "quick" fix, but it is a good one. Come to think of it, maybe it is about as quick as any.

As far as using young seedlings....yes you can. That's what I meant earlier. It's sort of like a donor. Approach grafting uses seedlings specifically in that context. The only problem is keeping the two trees together without disturbing the process. Very do-able, but can be unsightly and awkward. A very well-used technique to introduce different foliage characteristics on like genus, although I have never done it specifically for that reason..

If you have never tried it before, I would recommend researching it. It isn't hard, but only proceed if you feel confident. As always, it is best to "test" it on less valuable stock until you are satisfied with your proficiency. If you do it right, it is close to 100% successful. The junction scar is also less obtrusive than most approach grafts, but both will work.


Warmest regards,

John

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John Dixon

Si vis pacem parabellum

Stay off the trails of others, that's where the booby-traps are.

John Dixon

Here are some updated photos of the thread grafts, May 7, 2005.

John

Attached Images

	Thread graft May.JPG (67.2 KB, 77 views)
	Thread graft May2.JPG (61.5 KB, 66 views)
	TG3.JPG (61.8 KB, 73 views)

__________________
John Dixon

Si vis pacem parabellum

Stay off the trails of others, that's where the booby-traps are.

bonsaikc

John, terrific post! Thanks!

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midwestbonsai

great pictures, I haven't gone in to grafting relm yet. Someday

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Holokai

Nice "tutorial," John. Two questions though -

1) You said several times that the donor and host need to be kept close by eachother. Why is this? Are you actually running the branch through the hole before severing it from the donor?

2) Are you scraping off the bark from the branch you are grafting on, or are you inserting it whole?

Thanks!

- Chris

ripssurf

john..nice thread. great tree...

jeff

dtree

Is it possible to use a thread graft to create a new leader in the exact place that you want ?