All through October the town of Salem, Massachusetts is awash in witches. They are all dressed in black with pointy hats and try to look as forbidding and dangerously magical as possible.Though the word witch has assumed the dark cloak of evil, there are white witches as well, and witches' gardens could as easily have included healing herbs as well as herbs that are a little more problematical. Of course, as with so much in life, how a…