Mandrakes are both narcotic and hallucinogenic, and were used for sorcery and divination, but were also believed to cure sterility. Rachel kept trying anything.
Hitler practised mysticism, and possessed mandrakes. Nowadays mandrakes are used in some Wiccan rituals. And then there was the early 20th century cartoon “Mandrake the Magician”.
So Laban used divination. Many believe that the best way to find water is using a divining rod. If bent the right way it will point down to where water can be found.