A tumbleweed is a shrub of the genus Salsola. The plant has between 100 and 130 species native to areas of Europe, Africa, and Asia. Tumbleweeds colonize new areas by breaking from their roots in the fall and scattering seed as they are blown about by the wind.
Salsola tragus and other tumbleweed species were unintentionally brought to America in the 19th century by Ukrainian farmers. The tumbleweed became ubiquitous in the American West and consequently became associated with that area in the public consciousness. In Western songs and later in film, the tumbleweed emerged as a symbol of boredom, desolation, emptiness, and aimless wandering.
Tumbleweed is a very hardy plant, as it is resistant to salt and drought and is able to spread its seed over vast areas. The plant is able to procreate so well through this method that its seeds have not developed the protective coating or food stores seen in most other plants. In addition, the tumbleweed's taproot, which remains behind when the shrub breaks off to tumble through the landscape, is nearly impossible to destroy and grows a new plant every year.
Tumbleweed is considered a pest and an invasive species. It has little if any practical uses. The young shoots can serve as food for horses, sheep, and cattle, but they will only eat it in the absence of anything better.
Though the United States Department of Agriculture deliberately introduced tumbleweed into some areas of the United States around the turn of the 20th century, in the hope that it could feed cattle in times of drought, it now classifies the plant as a noxious weed. Tumbleweed is heavily controlled in the United States with herbicides.
Some tumbleweed species are used as food in certain parts of the world. Salsola soda is eaten raw or boiled in Italy, and Salsola komarovii is harvested for food in Japan, where it is known as "land seaweed." The seeds of the tumbleweed can be used to make flour, but they are quite difficult to collect.