"The moment they start trying to move into each other's pots, we'll know that they're fully mature"
From the Growth of the Mandrake as described in
Harry Potter and the Chamber of Secrets by J.K.Rowling
The legend of the Mandrake is...
That these humanoid plants grow under the gallows, having sprung from the semen of hanged men -and that when they are uprooted they give off a terrible scream which will instantly kill any living creature that hears it. The only way to harvest a Mandrake is to rope a starving black dog to the plant and then tempt the animal with some fresh raw meat. The dog will then dash forward plucking the mandrake from the ground -but that very action combines the lethal scream of the mandrake with strangulation by the rope. The unfortunate dog will perish -but you do now have a juicy, freshly harvested, mandrake.
Mandrake is actually...
One of the most infamous and most potent of magickal herbs and some types are very toxic. It is still widely used in Arabic folk medicine . The Mediterranean mandrake (Mandragora species) was probably introduced to England in the 14th century is now very rarely found wild.
Latin botanical names are not as reliable as they might appear, but it seems that the official name for the traditional Mandrake has now become Atropa mandragora which is the latest name for both Mandragora officinalis, and M. vernalis. There is also a closely related species M.autumnalis . Often called the Lesser Mandrake.
Some of the earliest references to mandrake are of it's use as a sedative. Apparently it was used by the ancient Greeks as an anaesthetic for battle-field surgery. It was also traditionally used as an aphrodisiac (see Genesis XXX.14), and one of Aphrodite's titles was "The Lady of the Mandrakes".
All true Mandrakes are related to the Solenaceae plants whichis a genus of poisonous plants, including Deadly Nightshade and the potato. So called “English Mandrake” is in fact Bryony root (Bryonia dioica.) and many herbalists will supply this as “Mandrake”.
Other plants are also sometimes known as "Mandrake". The poisonous American May Apple (Podophyllum peltatum) is known as American Mandrake and Ginseng has been called the Asian Mandrake. Galangal has also sometimes been called a "mandrake" due to it’s humanoid shape.