What sort of graft does my crabapple have? I have had a citrus that had a healed graft like this too. It really looks like the graft material has overgrown and taken over the original stump! Is that what this is?
My guess is that it was budded using either T or chip bud technique. In both cases a single growth bud is cut into the side of the stock trunk. When it has healed the top of the stock is cut off and the new bud starts to grow. A year or so later the bud has grown into a new trunk.
Thanks Shibui! Is there an advantage to grafting that way? It’s made for a nice graft on this tree, but others in the batch I picked this one from had some ugly bulges still.
Budding is usually used to make scion wood go further - a new plant from every bud instead of using 3 or 4 for other grafting methods.
The union in the photos looks a bit awkward to me. It is possible with good technique to graft so that the union is almost invisible but commercial production is not aimed at invisible grafts for bonsai. They are only interested in speed and success so grafts do not disappear for many years.
Yes, it will heal over eventually, a little quicker if you can cut the stub back a bit.
There may always be a slight change in colour on the bark there but the change of angle is probably good on this one.
Different bark colour, texture, etc is one reason people steer clear of grafted bonsai. Sometimes it is very noticeable but yours is not very noticeable.
Sometimes the scion and rootstock grow at different rates and there is a big difference in thickness at the graft. Should not be a problem with apples though.