Yes, tumbleweeds are a pain our butts, but the tumble is a necessary part of their survival. We were just talking on the air about how we never see "live" and "green" tumbleweeds, only the dead ones rolling fast toward your car's front grill on the highway. Once you see in the video below, what a tumbleweed looks like when it's growing, you'll know you've seen them a million times but maybe just never knew that's what they were! Here's why tumbleweeds absolutely must tumble: