Catling, PM. & Z Lucas. 1987. The Status of Calopogon tuberosus var. latifolius with comments on the application of varietal rank. Rhodora 89: 401-413.

Abstract: “To determine whether Calopogon tuberosus var. latifolius is worthy of recognition, and if so what rank is appropriate, data from herbarium material and uniform cultivation were analyzed. Plants corresponding to the original concept of Calopogon tuberosus var. latifolius from Sable Island were found to represent the tail end of a continuum of variation, making their formal taxonomic recognition inappropriate. In cultivation the Sable Island plants generally retained their short stature and wide leaves. Although there is a genetic component to the pattern of variation, the limits are arbitrary and some plants from Sable Island initially referable to one variety became referable to the other variety in subsequent years of cultivation. The concept of varietas is considered useful only in the sense of morphological discontinuity involving one or a few differences that have a geographic basis. The unique and genetically-based pattern of variation in Calopogon tuberosus on Sable Island is nevertheless of interest and is part of a general pattern involving both plants and animals.”