"hollow tree" is correct and it can be used in written English in many different contexts.
For example, "The birds nested in a hollow tree in the middle of the forest."
He showed you a hollow tree; you added the bees.
Another hollow tree; I had to stop myself.
Like you live inside someone, like an owl in a hollow tree.
0800: breakfast, leave message in bottle in hollow tree – "administration's attitude to Iran may be softening".
But what about the juvenile we filmed quietly placing a rock in a hollow tree trunk?
So there will be a hollow tree and a man in it, holding the rope.
The hammering did stop once the hollow tree long favored by flickers showed new life in mid-June.
A fairy cottage, a troll bridge and a hollow tree cast a spell on any who happen upon them.
You may see them peeping out of a hole in a hollow tree, one at a time, then disappearing.
Hollow tree trunks are now shower stalls; taps and pipes are made of eucalyptus branches and reclaimed copper, and the bar was once a fishing boat.
Although they sometimes utilize holes in the ground, these rodents usually nest in hollow tree trunks and rotting branches on the forest floor.
