This came in from a close friend of mine. Comments??
" About 5 years ago I gave a friend a tree grafted onto M27. It has grown to full size for its rootstock and is bearing fruit. But he and his wife have said they wished it were larger so it could be arched over the walk to meet a tree on the other side. I have the bright (or harebrained) idea to plant a more vigorous rootstock, maybe Bud-9, right against it, cut it off about 18 inches up, then do a bark graft into the scion, sort of like a bridge graft. Or something like that. Seems that the more vigorous rootstock would override the dwarfing effect of the M27."
Has anybody ever done anything like that? Comments?
This is a response to the above question by one of our members:
“Give it copper.
The dwarfing mechanism in trees is a genetic inability to metabolize copper.
Dwarf rootstock was discovered in sandy soils low in copper. Copper is
required to make lignin.
Dwarfing rootstock frequently reverts back to it’s full genetic potential
when planted in fertile soils.
This is why plants on dwarfing rootstock have so many disease issues;
copper is essential in the plant immune system.
Similarly, split bark is a copper deficiency. It’s not necessary to paint
trunks white. A little copper sulfate and molasses goes a long way.”
Seems plausible. It might work.
However, unless you’re just itching to experiment on your friend’s tree…
then, why not buy him another for the other side of the walk, and they will arch together over the top much easier than getting a tree to grow downward on the other side of a walk.