How can I achieve 1.5 mile (or even 300 foot) wide tree branches?

In my fantasy story, elves live high up in giant trees (or at least something similar to a tree). These trees are so massive, that entire cities can be built on their branches. The branches have flattened to accommodate these elves, as their presence is beneficial to the trees. This has the double bonus of flattening the 'ground' and providing more of it.

I recently added up the size of the kind of city I would like the elves to have on one of these branches. Combined with the right amount of open space around it, I've deduced that the branches need to be around 1 - 1.5 miles wide.

What do I need in place for a tree of this size to occur?

Notes:

• I've included some diagrams below, if you are having trouble picturing things.
• The branch only needs to be 1.5 miles wide at the widest point (the base of the branch, next to the trunk). I have nothing against the branch tapering off normally.
• The branches have flattened (at least near the trunk) as can be seen in the diagrams below.
• Magic is present, but I would prefer for it to have as little a role as possible. If such a tree simply cannot occur naturally, then I can work with magic tweaking things slightly until such a tree could exist. Just tell me what I need.
• The planet is earth-like.
• While the branches are huge, the tree itself does not need to be super high. I have nothing against it towering to the sky, but if it's a problem, the branches only need to be about 650 feet up.
• It seems that 1.5 miles is a bit of a stretch. Is roughly 300 feet any more realistic?

Diagrams:

posted about 7 years ago

Thomas Myron‭

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