Anyone who's ever watched Looney Toons and other hokey children's cartoons are probably familiar with scenes in which a small tumbleweed rolls across the scene to signify boredom. The visual equivalent of crickets chirping, a tumbleweed emphasizes the emptiness of what's happening.
In real life, small tumbleweeds like that, about the size of a basketball, roll around so long as there is a slight breeze and/or slope. Fullgrown tumbleweeds, however, can grow to the size of a pickup truck, and it takes powerful gusts to roll them across the landscape.
Tumbleweeds are actually trees with very shallow roots. Their branches grow very low to the ground and in a round shape, holding in thousands of seeds. When the wind is strong enough, the tree dislodges from its spot and rolls across the landscape and the seeds scatter - kamikaze propagation. Larger tumbleweeds can cause terrible destruction in high winds, as rolling dries out these trees and they shatter explosively upon impact.
A tumbleweed will see many remarkable things on its travels across the desert, only to continue the cycle of shallow roots and self-destroying reproduction. Would one come to rest on rock rather than sandy soil, the cycle would be broken.