Russian-Thistle (Salsola) Species in Western United States

Abstract

Russian-thistle populations in western United States consist of either of two species, or both, and are distinguishable at all stages in the field. Salsola pestifer is now replaced by an earlier name, S. iberica. The second species, S. paulsenii, prevails in many areas, especially in the southwest. Where growing together they appear to hybridize freely, resulting in populations exhibiting varying degrees of genetic introgression.