Tacuinum sanitatis Casanatense
It shines at night like a lamp, and when you see it mark it round quickly with iron lest it escape you. For so strong is this power in it, that if it sees an unclean man coming to it, it runs away. So for this reason mark it round with iron and dig about it, taking care that you do not touch it with the iron; but remove the earth from it with the utmost care with an ivory stake, and when you have seen the foot of the plant and its hands, then you shall at once bind the plant with a new rope, and you shall tie the same round the neck of a hungry dog, and in front of it place food at a little distance, so that in its eagerness to get the food it may pull out the plant.
Apuleii liber de medicaminibus herbarum (trans. George C. Druce)
I’m not sure mandrake farming is worth it, in the end. All that trouble just because you can’t find a clean man to dig up the mandrakes?