If broken, it drops the uncorrupted Mallorn sapling (unless a tool with the silk touch enchantment is used). Therefore it is advisable to bring along a stack of Gulduril crystals in case the sapling needs to be moved at all.
When the sapling is placed, nearby Ents will come and try to heal it. If it has been placed in Fangorn and there are no Ents nearby then the sapling will trigger the spawning of some. This does not happen instantly; it may take some time.
When three Ents who began healing the sapling have been slain, the Mallorn Ent boss will rise out of the ground to avenge its Mallorn kin.
The corrupt sapling can also be placed in a flower pot for future use or for decoration.