This midwestern species (previously known as Aster azureus Lindl.) is close to shortii (FNA 20), but differs in its less cordate leaves, less hairy phyllaries and larger heads; 2n = 32 (versus mostly 16). It is widespread over much of Ill., Ind. and Ohio, but perhaps unknown in more southeastern states (despite Ch, K, W; SERNEC). In Ky. there have been several reports of oolentangiense from western regions (M, FNA 20), but no colls. are verified here as typical of the species. It has been confused with shortii or other species in western regions of the state, and and occasional plants appear somewhat intermediate, including colls. from ALLE, FULT, HOPK, MCLE, MEAD and WARR. It has been recently reported from TRIG (D. Estes colls. at APSC); but these plants may be transitional to shortii or undulatum. Some introgression may be also expected with drummondii, urophyllum and laeve (FNA 20; see also St).