Salsa and guacamole wouldn't be the same without cilantro, and you can't make pizza without oregano or a mojito without mint. You can use peppermint to settle an upset stomach, ease arthritis pain with stinging nettle, and heal burns and wounds with aloe vera. And then there is cannabis--perhaps the most notorious and divisive herb of all. Despite the fact that herbs are often little more than weeds, cultures around the globe have found hundreds...