Extracted from Harry Potter: The Creature Vault by Jody Revenson
The root of the mandrake, or mandragora, can be used to revive those who have been Petrified. In Harry Potter and the Chamber of Secrets, Herbology professor Pomona Sprout assigns Mandrakes to her second year students, and she instructs them to wear earmuffs, as their cries can kill a person.
Visual development of the Mandrake’s leaves for Harry Potter and the Chamber of Secrets was based on the real Mandrake plant, so named because it appears to have a trunk and limbs. For the body of the plant, the creature shop designers realised that the look of the baby Mandrakes couldn’t be too cute or cuddly as their purpose was to be destroyed in order to make the Petrification cure. So they tried to make them as horrible and unlovable as possible, with wrinkled, screeching faces. More than fifty completely mechanical Mandrakes were created that made up the top halves of their flowerpots, with their movement achieved by one of the most basic special effects techniques—animatronic puppetry. The machinery for the Mandrakes was inside the pots, operated underneath the Greenhouse table by controllers. Once their animatronic action was turned on, the Mandrake would cycle through a series of writhing, wriggling motions that could be sped up or slowed down.
For Professor Sprout, Draco Malfoy, and a few others, Mandrakes were constructed that had similar movement but could be removed from their pots and still move their mouths and appendages, accomplished through radio transmitters.