It's quite hardy and does not need pollinator, so you need only one which is nice if space is limited. I guess it is since you are asking about one tree.
What are the plans with kiwi and tree? Train the kiwi up the tree? I had some difficulties establishing blackberries near the old trees, while same plants were doing fine further away, and I know kiwi has shallow roots, so as most trees, so I guess as far away from the trunk you go, better for the kiwi. You still can train it up the same tree if that is your intention, it does not have to be planted near the trunk to do that.
But then again, kiwi is a climber. It survived ages climbing up the bigger trees, so where did it grow if not near the tree? I don't know, it's confusing.
Permaculture in Croatia:
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