The Plant Person is a bridge between the Plant and Animal Kingdoms, being able to talk to plants (or at least understand them at an empathic level) and people alike. Their wisdom can be profound and alien, coming as it does from a plant rather than animal (let alone human) point of view. Biologically, he or she is either a motile plant or a person with a lot of plant-like characteristics: they may be able to photosynthesize their own food, drink water from their feet, and even regrow severed limbs. If they lean more towards the animal, they probably still need to eat, but it may be "nutrients" or dirt rather than cheeseburgers (though they just might; hey, at least it isn't people).