Cohosh is a plant with several common names, including bugbane and snakeroot, which reflect ancient uses of the root as an insect repellent and snakebite antidote. But nothing describes the plant's ornamental virtues like another of its names: fairy candles, which refers to its tall, graceful wands of creamy white flowers, visible even in twilight. Here's what you need to know about cohosh before adding it to your outdoor space.