Hi everyone. I started this on the “questions not deserving a whole thread” and decided to copy it over to see if I can get a few other opinions. I was planning on doing the work this year so hopefully I can get a few good solid opinions. This is the copied post
I have kind of an Odd question and I can’t find that much information to answer it. I have been doing mostly whip and tongue grafts with my My fruit trees. The idea is to try and put more than one variety on the tree by grafting a new variety on to a developing scaffolding branch. I know this is widely done on this website and everywhere but my question is where the graft is attached does it make the branch weaker? So for example I have purchased a Oh Henry Peachtree and plan to do four scaffolding branches one of A different variety than all the rest. Oh Henry, Haro diamond, Cresthaven and elberta. Am I going to end up with a bunch of scaffolding branches five years from now that are weak where it is grafted?
I am afraid the weight of the fruit pulling the branch down will snap at where the graft is.
I’ve been told how to whittle the interstem (the branch) prior to attaching the graft, as though it were crucial to maintaining the ultimate strength of the graft union to make either a horizontal or a vertical cut, but I can’t remember which is correct. In fact, I believe I’ve seen both ways advocated vociferously, so I’m just gonna leave this here and enjoy whatever controversy ensues.
Some say that your scion will fall out if you make a vertical cleft. Others say that your interstem will split under load if you make a horizontal cleft. I sort of lean toward making a vertical cleft.
Well dang! So would there be a better way to graft scaffolding branches on to the tree??
Do you think it would be better to basically top graft a new section on the tree every year and pick one scaffolding branch from each section? so in the end it would have four small sections grafted into the trunk. So then the graft originates in the trunk of the tree and not wear it there is a weight pushing down in it?
Grafting scaffolds on a peach tree should be just as strong as naturally grown ones, after a couple seasons.
If you think about it, it’s the new growth which adds structural strength to a branch, or branch attachment. Old wood will not fuse itself together. It’s the new growth which adds more strength year to year.
When a normal graft bark graft is done, the scion wood is no bigger than 3/8" most of the time. The cross sectional area of 3/8" circle is only. 0.11 inches. Now lets assume the graft grows to 1" after a couple seasons. Now the cross sectional area is about 3/4 of an inch. However 0.11 inches of cross sectional area is not fused together (and will never be fused). It’s only about 15% of the cross sectional area that is not fused.
This may seem significant, but any structural engineer will tell you that the “core” of your round limb or branch offers the least structural support anyway, even if it was “fused” there. Most of the structural support of rounds is toward the outer edges of the center of the radius. The center of the radius offers very little structural support. The same is true with beams. The middle of the depth of a beam offers little structural support. That’s why electricians can drill all kinds of holes for electrical cables in the middle of your floor joists without compromising the structural integrity of the joists. It’s the outer edges of the members which provide the most structural support.
Now back to your tree. Fast forward to year three. After 3 years your scaffold should be 2" in diameter at least. The cross sectional area is now about 3 inches. But remember 0.11 inches of cross sectional area is not fused. But that is now only about 3.5% of the total cross sectional area. And since it’s in the center of the branch, it becomes completely insignificant in terms of structural capacity.
If you are talking about a cleft graft where the trunk is already several inches in diameter, then yes it could be a weak point for several years. Or if there are is a high degree of incompatibility at the graft union, then it could become a weak point. But for all practical purposes, grafting scaffolds on your peach tree will be just as strong as natural ones after a couple years, provided the angle of graft is not too steep.
Thank you for the reply! That makes sense with the structural load. It’s funny you brought up the floor joist as a point. I just recently called BCI floor joist company because I had to drill a few holes in my floor joist for pipes. Haha.
Thanks for the explanation and reassurance. I will keep as planned with my peach tree project.