From the Super Mario Wiki
Big Bone Piranha Plants are the giant versions of Bone Piranha Plants, as well as the undead versions of Big Piranha Plants. Like all the other undead enemies from New Super Mario Bros. 2, they are similar to their non-undead species, with the same strengths and weaknesses. Like many of the other enemies in this game, Mario and Luigi can defeat this enemy with a single gold fireball and receive Coins. Like normal Bone Piranha Plants, it cannot be harmed by fire, but can be destroyed with either a Super Leaf, Gold Flower, Mega Mushroom, or a Star. They appear in World Mushroom-, World 4- and World 5-.