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Desmanthus virgatus (L.) Willd. has significant fodder potential, but its seeds have high and persistent levels of physical dormancy which interfere with its field establishment. The purpose of this study was to analyse the variability of physical dormancy in three populations of seeds from humid and arid regions of Argentina, grown and collected in different years and locations. The hardseededness and the percentage of seeds with intact lenses after a softening treatment and the seed coat thicknesses were compared. The variability observed in the obtained percentages of hardseededness, intact lenses and seed coat thicknesses was related to the origin and the environment in which these seeds had developed. Although further work is needed, arid environments seem to favour the development of thicker seminal layers, being an important factor that determines the impermeable nature of the seeds in this species. This information is required for future genetic improvement programs and for understanding the evolutionary process of the populations of this species in different environments.