This northern "pussy willow" does not extend into the southern Appalachians (K, W); remaining unknown in Tenn. and N.Car. S. discolor is rare in Ky., and perhaps largely restricted to cool damp valley bottoms in northeastern regions. It cannot be relocated at some historic localities. There has been considerable uncertainty about most identifications of this species in Ky. Colls. reported by B from Appalachian regions were not mapped by Argus (1986) but need to be rechecked (perhaps at GH or US). The record from OLDH (Argus 1988) should probably be transferred to ericephala. S. discolor is variable, with a polyploid series (2n = 76, 95, 114), and can form fertile hybrids with humilis (2n = 38, 76). All other species of section Vetrix in Ky. may just have 2n = 38 (Cr; FNA 7). S. discolor differs from humilis and occidentalis as follows (FNA 7, W): leaves glabrate (versus permanently pubescent at least below),sparsely pubescent when young (versus densely villous or tomentosa), not revolute (versus revolute). Also, catkins tend to be larger: male, 23-52 x 12-22 mm (versus 6.5-34 × 5-19 mm); female,25-135 × 12-33 mm (versus 9-55) × 5.5-19 mm). The whole discolor-humilis complex (in section Vinarella) differs from eriocephala (section Cordatae) and sericea (section Griseae) as follows: leaf margin entire or crenate to slightly and irregularly serrate (versus serrulate or serrate). Further characters would be desirable.