Depending on the species, weeds spread with the help of wind, water or by other means, but human factors seem to be the best way to spread weeds from field to field, across a state, from state to state and even from one country to a different one.

In this video, Dr. Wesley Everman, Extension Weed Specialist at North Carolina State University explains how specific strains of Palmer amaranth and waterhemp were found to have traveled from other parts of the U.S. and made a home in North Carolina.