Remember the video in this topic Napoleon’s army planted pear trees fact or fiction? and the comment on the poor quality of the fruit on those ancient pears?
I’ve recently learnt that if you plan to get a graft from a good quality old pear tree somewhere, don’t wait until you pass it by in the right time some years ahead. The tree may actually (I guess) revert to rootstock top to bottom/left to right. They hardly have a system… It has happened to this perhaps 120-150 y.old pear on our property.
20 years ago the whole tree bore loads of mid to large sized pears of a local winter variety that ripens in storage since Xmas, stores until april and has excellent taste and thick skin.
Slowly the bottom branches 1m above graft started showing rounder and less hairy leaves and fruit the size and shape of a squised golf-ball. (Very sweet but bletting on the tree, still good for distilling, though.) Then some old branches broke off higher in the tree and the changes appeared there as well. More one spring when a number of larger trees (cherries, walnuts, mullberries, apricots etc) in the area leafed out late on the southern side - perhaps damage from winter sun. Last year there was one branch left of the grafted variety atvabout mid height.
Fortunately, we have one other tree of the same kind.
I’ve seen this happen with ancient pears in the area, some reverted completely, som are part way through. It seems as if the tissue DNA travelled up to the top branches (not new, but still growing).
I’ve tried to find out how it works, but I must be asking the wrong questions, so if someone knows or has links to some papers, please let me know.