About a hundred years ago, hemp was grown in many parts of the U.S., and the hemp fibers were made into rope. Later, that industry died out when modern fibers came around. However, if you go out into the fields where the hemp was grown, there are volunteer plants still coming up. That is extremely low-THC stuff, and modern "weed" is the high-THC stuff that will show in a drug test. I suppose that it is possible for low-THC stuff to show in a drug test, so the only safe way is to avoid it altogether.