This alien is established across most of the U.S.A., especially western regions, but it remains rare to absent in southeastern states. Although widely scattered in Ky., records are few and mostly date from 1920-1950. P. bulbosa is a variable species; 2n = 14 to 45 (FNA 24). In addition to having bulbous culm bases, most plants in North America have bulbiferous (viviparous) spikelets and are referable to ssp. vivipara (Koel.) Archang. Plant with non-bulbiferous spikelets are known only from Ohio (FNA 24).