'Delayed incompatibilities between scion and rootstock'?

18 years ago

I have Lee Reich's book "Uncommon Fruits for Every Garden" and about the medlar he writes:

"Because of delayed incompatibilities between scion and rootstock, a medlar tree should be planted with its graft union a couple of inches below soil level. Soil covering the medlar scion eventually will induce the scion to form its own roots. This rule cannot be followed with a medlar trained as a standard by being grafted on some ramrod-straight rootstock"

What does he mean by "delayed incompatibilities"? So, like what, a scion will just like jump off the rootstock and walk away after a few years? What the heck could happen to a graft after a few years other than wind damage breaking it?

Furthermore, I want to try grafting medlar onto bradford pear to make a larger medlar tree (medlar grows terribly slowly and is low-bearing). If the graft union takes and no weird graft hybrid results, will I have to worry about "delayed incompatibilities"?

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Comments (3)

ashok_ncal
18 years ago
Peanuttree,

No, scions won't jump off from rootstocks and walk away (although that certainly would be a sight worth seeing), but they can slowly decline and die due to delayed incompatibility, despite initially "taking" and growing for a few years.

I think medlars are said to be *generally* compatible with pear rootstocks, but I'm not sure about "Bradford" specifically.
calistoga_al ca 15 usda 9
18 years ago
The case of compatibility may not be apparent in the first few years, but the graft never seems to blend into the bark of the tree. With time the graft area is noticed to be swelling and the tree seems to lacking vigor. Soon dieback of some branches is noted and suckering from below the graft increases. In another year or two everything above the graft is dead. Not exactly "jumping off" but never the less it is gone. Al
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denninmi
18 years ago
I had a tree years ago that had this problem -- I wish I had pictures of what happened to it, it was quite spectacular. Dumbest thing is, I can't remember what kind of tree it was -- I know it was either a cherry or plum, definitely wasn't an apple.

At the graft union, which was maybe 6" above the soil line, both halves of the graft grew into a large, bulging knob over a few years. One day, in the summer, I came out, and the tree had split nicely right in the center of the knob. Both of the surfaces where they tree had been joined were largely covered with bark and corky tissue (suberin, I believe it is called). I don't know how it got moisture and nutrients up into the top, because it seemed to lack any real vascular connections, everything was sort of dry and barky/corky. But, the top of the tree was nice, green, and healthy when it broke off, and it happened on a clear, sunny, calm day.

So, yes, mine did literally jump off of its rootstock.

I guess graft/host delayed incompatibility is sort of the equivalent of rejection of a transplanted organ years later -- the immune systems of the respective tissues at some point recognize each other as foreign, and take steps to "wall off" the offender, resulting in their eventual mutual destruction.

'Delayed incompatibilities between scion and rootstock'?

Comments (3)

ashok_ncal

calistoga_al ca 15 usda 9

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