Just exactly what color is the cambium anyway?

[oscar]

The fact the pruning cuts can bleed sap, is not proof that xylem once separated reconnects.

@jujubemulberry

I also feel that any sap flow from roots to scion at the time of grafting is at least as important as having to wait for cambium to reconnect, because if that concept is the only thing to rely on, one will have to wait for new xylem to be fully differentiated before actual root-to-scion flow is initiated.

The phloem usually differentiates before the xylem. And that would be the first access the scion has to resources after grafting.

if you look at this topic. From the 3e picture onwards.

Inside a graft

Ever wonder what that graft looks like inside? Had a pear tree give up the ghost, soo let’s take peek inside. [image] [image] [image] [image] [image] [image]

You can clearly see where the stock and scion where grafted. And you can clearly see that the xylem did not reconnect. And the rootstock blocked the severed xylem, visible from the discolored lines. Just like you see when the tree is trying to block of a fungus growing into the wood.

This might not be hard evidence (you’d need a controlled experiment for that) but it at least makes it likely that grafts with bad xylem contact do just fine.

Always go for good cambium contact over good xylem contact. All sources on grafting if ever seen emphasize cambium contact is most important during grafting.