This species is widely cultivated in North America (especially as "var. glabrum") but it is not known to escape (FNA 26, K; missouribotanicalgarden.org). There has been much recent molecular analysis of Allium phylogeny (e.g. Freisen et al. 2006, Li et al. 2010), but reliable keys are not yet available for treatment of all wild and cultivated material in North America. A. senescens has a horizontal or oblique rhizome; bulb tunic entire, not becoming fibrous except perhaps near apex; leaves 7-12 mm wide, scape flat; 2-angled, 25-60 cm tall (Flora of China 24; missouri botanicalgarden.org). It appears to belong in subgenus Rhizideum sensu stricto; see also notes under tricoccum. The treatment of Allium in Flora of China 24 could be deepened and expanded to include North American species of the genus.