In the Western movies We often see “rotary shrubs” that move in the desert between cowboy and sheriffs pushed by the wind, i rollacampi or “tugerweed“But what are they actually? It is not a pile of tangled sticks but of particular vegetable structures of some plants which, once dry and for the end of the life cycle, yes they detach from the ground and, rolling like a ball pushed by the wind, they spread their seeds. The rolling tank or steppicurs can be the entire plant -free plant, or, depending on the species, a cable fruit or an inflorescence.
Different species can form these “vegetable balls” symbol of American deserts, most belong to the amaranthaceae family and the genre Sausage. There Tragus sauce, The best known, it is a herbaceous and shrub plants capable of growing on alkaline and saline soils colonizing areas with little vegetation or deforestation.
It is in fact originally from the arid and semi-arid regions of all Europe and of theCentral Asia while it has become a highly species invasive in North America. It is thought that the seeds of these plants arrived for the first time in the current United States in 1870, in the South Dakota, probably together with flax seeds imported from the Russian empire. This species, today widespread in all states, on its arrival on the American continent spread rapidly, preventing the native vegetation and wildlife from prospering in infested areas, creating many problems for farmers.
There Salesla tragus It grows into rounded shape, transforming itself from a tender seedling to a rigid and thorny plant and, once dry and mature, yes detachment from their roots e roll pushed by the wind. This is an effective strategy to disperse over 250 000 seeds which produces, which are shaken by the movement and scattered throughout the ground. Once scattered, to sprout, the seeds need ideal conditions: a daytime temperature of about 20 ° C and night of 5 ° C. For their ability to spread in an uncontrolled way due to the air currents, the rolling boys have created several logistical problems in some US cities, accumulating themselves in various areas and representing a danger for road accidents or for fires due to their high flammability, as happened in Utah and Nevada in 2024.
