Fall, fallen, fell, felled.

Just for info.....

fell tr.v. felled, fell·ing, fells To cause to fall by striking; cut or knock down: fell a tree; fell an opponent in boxing. To kill: was felled by an assassin's bullet.

So, the tree felled across the tree was somewhere correct. It did experience some kind of force that caused it to fell.

But if it is wrong, just a grammar mistake lor.

Source: Dictionary.com