Double grafted fruit trees... greater disease resistance using multiple source material

I was chatting to a chap at our local nursery where they specialise in apple trees. He showed me a few trees that had been double grafted:



Fruit wood grafted on top
Disease resistant material between, forming a six inch section of stem
root stock beneath

The theory was that by grafting a section of disease resistant wood between the root stock and the desired fruiting wood you get better overall disease resistance characteristics from the final tree, while still keeping the size restrictions of the desired root stock.

Anyone got any experience of these trees?

That's commonly called "interstem grafting" and in addition to selecting for dwarfing and disease resistance it also can be used to bridge incompatible scions and rootstocks in some cases. The three major draw backs are that the trees tend to sucker more than singly grafted trees, they have twice the number of breakable graft unions, and they are more work to graft over.

Thanks John,

Good to have a name for it!

I was thinking "that sounds like more work" and "don't grafts fail from time to time?". I guess once the tree is established you might get a better product out at the end. It does suggest that there might be some potential breeding super disease resistant trees specifically to use as the interstem material... no need to worry about size as that is controlled by the root stock, and flavour is irrelevant.