This is close to capitellata, and has a more southern range, being most common on the Coastal Plain. Intergradation is known in southern regions (FNA 23), and suspected in Ky. R. glomerata usually has distinct achenes (FNA 23, J, LeBlond in W): averaging larger, up to 1.4 mm wide (versus 1.2 mm), suborbicular (versus pyriform), distinctly truncate at the summit (versus tapered), pale-umbonate on the faces (versus uniformly brown), and with a thickened wire-like margin (versus usually with a less distinct margin). It is generally more robust, with leaves up to 5 mm wide (versus 3.5 mm).