Strange Trees are the unofficially named objects in Devil May Cry 4. They rot when they come in contact with the Sephirothic Fruit, opening up new paths for Nero and thus functioning in a similar way to Sealed Doors. The origins of these trees are unknown, although they are probably a result of the demon infestation in the forest.
The largest tree of this kind is found by Nero in the Order of the Sword's HQ, inside Agnus's Room. It grew so large that it prevents a bridge within the compound from lowering. After Nero nearly defeats Agnus in battle, Sanctus kidnaps Kyrie. This enrages Nero so completely that he punches the root-covered floor of the room several times, causing the large tree to disintegrate and allowing him access to the other section of the headquarters.
Strange Trees block off several paths throughout the maze-like Mitis Forest, forcing Nero to take a certain route. After Nero obtains the Sephirothic Fruit in Mission 7, Strange Trees blocking paths will disappear when examined.