Hekate’s association with Mandrake (Mandragora officinarum) comes from it being mentioned in the Argonautica as one of the plants in “Hekate’s Garden”.
This is an short extract from the book Circle for Hekate (V.1):
The root of this plant has narcotic and hallucinogenic properties. It was used historically to treat melancholy, and as a surgical sedative by ancient physicians.
You can read more about Mandrake at the Royal Horticultural Societies website: https://www.rhs.org.uk/Plants/10849/Mandragora-officinarum/Details
Page updated: Feb 2020. The previous article contained errors related to the botanical names of the plants and their uses.