Tumbleweed

A tumbleweed is a structural part of the above-ground anatomy of a number of species of plants, a diaspore that, once it is mature and dry, detaches from its root or stem, and rolls due to the force of the wind. In most such species, the tumbleweed is in effect the entire plant apart from the root system, but in other plants, a hollow fruit or an inflorescence might serve the function. Tumbleweed species occur most commonly in steppe and arid ecosystems, where frequent wind and the open environment permit rolling without prohibitive obstruction.The tumbleweed dispersal strategies are unusual among plants; most species disperse their seeds by other mechanisms. Many tumbleweeds are ruderal species, opportunistic agricultural weeds. Tumbleweeds have been recorded in the following plant groups:Some ruderal species that disperse as tumbleweeds are serious weeds that significantly promote wind erosion in open regions. Their effects are particularly harmful to dry-land agricultural operations where the outside application of additional moisture is not practicable. One study showed that a single Russian thistle can remove up to 167 liters (44 gallons) of water from the soil in competition with a wheat crop in one year. The amount of water removed from fallow land more subject to erosion would be even more damaging.The tumbleweed's association with the Western film genre has led to a highly symbolic meaning in visual media. It has come to represent locations that are desolate, dry, and often humorless, with few or no occupants. A common use is when characters encounter a long abandoned or dismal-looking place: a tumbleweed will be seen rolling past, often accompanied by the sound of a dry, hollow wind. This is sometimes used for comic effect in locations where tumbleweeds are not expected, but the emptiness is obvious. Tumbleweed blowing between two theatrical characters can also be used to emphasize tension in a western style duel or standoff.