Dieteria canescens (Pursh) Nutt. Dieteria canescens (Pursh) Nutt. in Trans. Amer. Philos. Soc., n.s., 7: 300. 1840 sec. Villaseñor 2016=Machaeranthera spinulosa Greene in Pittonia 4(20C): 24. 1899 syn. sec. ???