Populations of var. montanum in Kansas and Nebraska have an unusually high proportion of branched-stem plants mixed with simple-stemmed ones-even within the same clump (Great Plains Flora Association 1986). Although branched stems are found occasionally elsewhere in the taxon´s range, the high incidence in this region is unusual and may be related to the distributional approach of S. angustifolium, with which it often has been confused.
Canadian populations of var. montanum tend to have narrower bracts and other less pronounced interspecific differences than do populations elsewhere. These populations can easily be confused with S. mucronatum, which consistently has some purple in the spathes and usually has a shorter outer spathe, and with S. septentrionale, which lacks emarginate outer tepals and has a very long and narrow outer spathe.
From Flora of Indiana (1940) by Charles C. Deam
This species was reported from many parts of the state by early authors before our manuals recognized Sisyrinchium albidum. Probably most of these reports should be referred to the last named species [S. albidum]. Peattie reported this species from the Calumet Region where I, also, have found it. It is infrequent in moist soil on the low, open dunes along north Clark Street in Gary about an eighth of a mile south of Lake Michigan. Not yet known from any other county.