Two unrecorded Elymus taxa (Poaceae) newly added to Korean flora: E. humidus and E. shandongensis

Given that the Korean genus Elymus L. (Poaceae) is often confused with Agropyron Gaertn., the categories and characteristics of Elymus s.l. have been reviewed morphologically. Two unrecorded taxa of Elymus, E. humidus (Ohwi & Sakam.) T. Osada and E. shandongensis B. Salomon, not previously recorded in Korean flora to date, we report here as an unrecorded species based on samples collected from Chungcheongbuk-do, Gyeongsangnam-do, Jeollanam-do, and Jeollabuk-do. E. humidus is distinguished from other taxa in terms of its habitat around riversides, erect inflorescences, spikelets appressed to rachides of inflorescence, and new individuals asexually propagated at the lower nodes of aerial stems. E. shandongensis is similar to E. tsukushiensis var. transiens (Hack.) H. Osada but is distinguished by the flowering time, slightly curved inflorescences, number of veins of the glumes, and spikelets appressed to the rachides. Descriptions of the two unrecorded Korean taxa, photographs, and keys to neighboring taxa are presented.