Cave under a tree or rot in the heart

[Alexandr Fedoseev]

Of course it can be, but it's not uncommon for trees to have voids like the one in the yt vid and it doesn't mean it was unsafe.

 

Maybe you misunderstood me. During the work there was nothing dangerous.

But such a tree is a danger to the inhabitants. Poplars and so often fall. When the root rot, the trees become even more brittle.

[Alexandr Fedoseev]

I thought the point was simply that the tree was heart shaped ?

 

Yes, it seemed to me that this would be an interesting metaphor - "Rot in the heart"