For most of us, memories of veggies are far more likely to involve unpleasant parental dicta about not leaving the table until one has cleared one’s plate. You know what I mean. Some of us sat there for hours, staring resentfully at lima beans.

Historically, however, vegetables have packed a more exciting punch. The garden, traditionally, has been a hotbed of aphrodisiacs. Some sex-food picks may have originated from sheer physical resemblance. The medieval Doctrine of Signatures, for example, argued that the Almighty left medical clues (“signatures”) scattered throughout the natural world, pairing helpful resemblances to body parts with the ailments to be cured. Thus walnuts—wrinkly, like the surface of the brain—were intended to treat head wounds and headaches; and