Where the superpowers of superweeds come from

Superman had the yellow sun of earth, spiderman had a radioactive spider-bite, but what about superweeds, where does their super power (surviving application of Round-up/glyphosate) come from? To understand how superweeds survive, we first have to understand why normal weeds (the Jimmy Olsens and Lois Lanes of the plant world) die. <-- last superhero reference of this post I promise.