over the past 30 years I have done approx. 150 of these bud grafts. They seem to take best when grafted just at bud out, that is the buds are swollen but not yet opening (this is the point of first sap flow). I did the first of these grafts for one of my family members peach farms (they wanted to branch out to nuts other than pecans so they decided on chestnut) and the first takes are still producing and should do so for another 40 years at least.
Greffe de châtaigniers sur hêtres