In today’s sidra it appears as a magical herb capable of overcoming infertility, as in the story of Rachel (Gen. 30) who found it extremely difficult to conceive.
The use of the mandrake for this purpose was widely recognised in the ancient world but whether it really was effective is not certain (Nachmanides says he has not seen any medical evidence to prove the assertion).
The herb does contain ingredients which can cause delusions and temporary unconsciousness; some of the Talmudic rabbis believed it could chase away demons.
A more rational approach insists that it was not the mandrakes that allowed Rachel to become pregnant but the prayers that she addressed to God from the depths of her heart.
It is prayer that expresses her anguish, though it might be that the mandrakes calmed her down and relaxed her and thus enabled conception to occur.