By Amy Weiss

Sep 26 2019

Tumbleweeds aren’t restricted to one species or plant family, but are an adaptation that has evolved a number of times to disperse seeds by having a portion of the plant break away from the roots and roll away in the wind. Tumbleweeds are native to steppes and other arid ecosystems, which allows the tumbling plants to roll unimpeded for long distances while dropping their seeds. 

That icon of the American West, the common tumbleweed (Salsola tragus s.l., shown above), isn’t originally American. Also known as Russian thistle, it was introduced to the United States in the 1870s in contaminated flax seeds, and had tumbled from the Dakotas to the Pacific coast by the turn of the century.¹ Excessive grazing that depleted the natural flora, agriculture, railroads, and even atomic bomb testing in Nevada,¹ all allowed Russian thistle to roll right along making itself at home.

Click on the herbarium specimens below to see more examples of tumbleweeds and you can watch Russian thistle tumble.² 

A Closer Look

¹ Young, J. (1991). Tumbleweed. Scientific American 264(3): 82-87. Retrieved 30 Aug 2019, from http://www.jstor.org/stable/24936831

² Deep Look. (2018, May 1). Why do tumbleweeds tumble? Retrieved 30 Aug 2019, from https://www.youtube.com/watch?v=dATZsuPdOnM