One of the bark grafts I made this past Spring died suddenly (photo at right). The graft was still standing up straight and tall but all the leaves had turned brown. This warranted closer inspection.
I immediately focused in on the graft union (photo at left). Even though I had painted the graft union white, I could see that the scion had been broken right at the very top of the stock. I carefully stake every bark graft but is obvious that I did not secure the stake tight enough to the tree to prevent the scion from rocking back and forth in strong winds. I had used black tape to secure the stake to the tree but upon inspection I found that I could wiggle the stake just enough to allow the breakage observed to the scion. In the future, I'll need to start bringing a cordless impact driver and wood screws to the field when installing stakes on bark grafts. Two screws placed through the stake and into the stock tree should help hold things rigid.
The breakage of this one graft encouraged me to start looking at other bark grafts I made this year. I was especially interested to see how each scion grew at the very top of the stock. The photo at right is typical. This scion appears to be trying to creep over the top of the stock. You can also see how new tissue is forming up from the cambial layer of the stock to grab onto the side of the scion. At this point, the scion can still break easily unless it is help firmly in place with a strong stake and plenty ties.
I noted that bark grafts applied to 1 to 1.5 inch diameter stock trees can close over the grafting wound very quickly. The tree pictured at left was grafted this year and has nearly grown completely over the stock wound.
I've been grafting pecan trees for 40 years now. Every year presents a new set of challenges to overcome and lessons to learn. It is a good thing I've got plenty of young seedling trees coming along to teach me even more lessons about pecan grafting in the future.