Tumbleweed
[1] Xerophyte tumbleweed species occur most commonly in steppe and arid ecosystems, where frequent wind and the open environment permit rolling without prohibitive obstruction.
[8] It now is a noxious weed throughout North America, dominating disturbed habitats such as roadsides, cultivated fields, eroded slopes, and arid regions with sparse vegetation.
[16] Several Southern African genera in the family Amaryllidaceae produce highly optimised tumbleweeds; their inflorescences are globular umbels with long, spoke-like pedicels, either effectively at ground level, or breaking off once the stems are dry.
When the seeds are about ripe, the fruit remain attached to the peduncles, but the stem of the umbel detaches, permitting the globes to roll about in the wind.
The light, open, globular structures form very effective tumbleweed diaspores, dropping their seeds usually within a few days as the follicles fail under the wear of rolling.
Also in the Asteraceae, Lessingia glandulifera, native to America, sometimes forms tumbleweeds; it grows on sandy soils in desert areas, chaparral, and open pine forests of the western United States.
[24] Very similar in habit to Anastatica, but practically unrelated, are the spore-bearing Selaginella lepidophylla (a lycopod) and earthstar mushroom family (Geastraceae).
Tumbleweeds thrive in disturbed soil and are a major contributor to native plant extinctions and wildfires, being highly flammable and bouncing over or rapidly growing in land cleared of vegetation between fields or areas of forest as firebreaks.
One study showed that a single Russian thistle can remove up to 170 L (44 US gallons) of water from the soil in competition with a wheat crop in one year.
It sometimes happens that species of large tumbleweed, especially if thorny, can form aggregations that are physically hazardous and can block roads and cover buildings and vehicles.
In residential areas, an example was the town of Mobridge, South Dakota, where in 1989 tens of tons of large tumbleweeds ("Russian thistles") that had matured in the dry bed of nearby Lake Oahe buried many houses so deeply that mechanical equipment was necessary to remove it, release occupants and counter the fire hazard.
The seed heads of the weed, known locally as "hairy panic", had piled several meters deep in some places, forcing residents to spend several hours removing it to regain access to their homes.
[32] On 18 April 2018, strong winds and neglected maintenance of neighboring private land brought a large number of tumbleweeds into Victorville, California.
[33] A similar incident occurred on 31 December 2019, when high winds dislodged a large number of tumbleweeds on the Hanford Reservation northwest of Richland, Washington.
In some cases of inadequate fencing, they can get entangled in electromechanical equipment such as clarifiers and mechanical aerators leading to increased energy use and labor cost associated with operating and cleaning.
[37][38][better source needed] This motif has become clichéd,[39] with the result that it is nowadays primarily used with humorous intent – for example when a short but embarrassing moment of silence occurs during a scene.
