What is his monetary incentive to do this?
Could be a limb from itself that just happens to graft itself to itself.
This could very well be it. I highly doubt two separate trees merged and cellular connections formed to meld into one tree. It would be like two organisms forming a super organism. Combining. When has anyone seen that ever?
This actually happens all the time in nature - it’s called inosculation or natural grafting, where trees of the same species (and sometimes different species) can fuse their vascular systems together and litterally become connected organisms sharing nutrients and water through their merged tissues.
People do it with fruit trees all the time. As the other commenter said, it’s called grafting.
You can combine apple and pear trees into one or put a tomato plant on top of a potato. This definitely isn’t uncommon.
And also in nature different species often work together in some kind of super organism. Just think of our gut bacteria, orchids growing on trees, symbiosis between mushrooms and trees etc.
