We present new and remarkable flowering plant, moss, and lichen taxa to the flora of Estonia, which we recorded in dry grasslands on the island of Saaremaa. New to Estonia are Bryum radiculosum BRID. (Bryophyta - Bryaceae), Caloplaca lithophila H. MAGN. (Lichenes - Teloschistaceae), and Festuca oelandica (HACKEL) K. RICHTER (Spermatophyta - Poaceae). Agonimia globulifera BRAND & DIEDERICH in SÉRUSIAUX & al. (Lichenes - Verrucariaceae) was previously mentioned in a note by S. B. but without detailed ecological information. For Allium schoenoprasum subsp. schoenoprasum var. alvarense Hyl. (Spermatophyta - Alliaceae) and Crepis tectorum subsp. pumila (LILJEBLAD) STERNER (Spermatophyta - Asteraceae), diverging opinions existed in the literature as to whether they occur in Estonia or not and how they should be discriminated from the respective typical infraspecific taxon. We give detailed morphological descriptions of the collected specimens and characterise the stands of the newly found taxa ecologically and sociologically. Most of the new records originate from the Crepido pumilae-Allietum alvarensis (Sedo-Scleranthenea), an open alvar community of shallow, skeletal soils, whose stands are subject to inundation in winter and severe drought in summer. From a phytogeographical point of view, the occurrences of the three flowering plant taxa on Saaremaa are most remarkable, as they have been previously thought to be endemics of Öland and Gotland. They presumably have arisen following the glaciation under the harsh environmental conditions of the open alvar communities from their widespread and ecologically plastic ancestors.