Proso millet has become a major weed in North America during the past 20 yr. Experiments were conducted to assess the role of the soil seedbank in proso millet's success as a weed. Proso millet has at least eight distinct biotypes, all weeds, which exhibit a wide range of seedbank behavior. At one extreme, weed biotypes resembling crop varieties form transient seedbanks where all viable seed germinate or die before newly ripened seed enter the seedbank. In contrast, the black- and dark-red-seeded biotypes form persistent seedbanks that last several years in the soil. These latter seedbanks differ from those previously described in that there is always a fraction of the seedbank that is not capable of immediate germination. The black-seeded biotype of proso millet can establish a persistent seedbank quickly and that makes the weed very difficult to eradicate.
