Leaving understock on young graft
Well, I'd like to continue this discussion that was briefly entertained on another current thread. I'm interested in learning more about leaving the understock on a young graft to promote the health of the new graft. It was recommended for the case of young Pinus contorta 'Chief Joseph' that plant health and overall performance during at least the young years is drastically improved if a single branch from the understock is maintained
It's well known that leaving the understock on is beneficial for miniature and gold-colored scions, since these types of scions will produce a limited amount of photosynthate. The reason is obvious, the understock leaves will produce food for the roots and thereby contribute to the well-being of the entire plant.
Now, I have also heard that in certain cases, the rootstock is left on and even if it has no foliage, that it will still be beneficial to the plant's health and it is about this that I'm curious. To me it is surprising that a little understock stem has so much carbs stored that it can feed the plant from it's reserves, for years. Since this came up (in the other thread) I would like to learn more. Which plants might be good candidates for this sort of treatment, and why would you do this rather than leave on a full branch with leaves (one which is not shading the scion of course)? Why would you "remove the understock gradually" rather than leave a branch on until no longer needed and cut it off all at once?
Thanks, and please jump in with any other questions you have on the topic :0)