In the present 4th contribution further taxa are reported as new to the flora of South Tyrol. Among them are the adventitious and casual Claytonia perfoliata, Sonchus tenerrimus, and Sorghum bicolor. Other adventitious species are probably already or about to become (locally) established: Akebia quinata, Barbarea bracteosa, Eragrostis frankii, and Mimulus cupreus; definitely naturalized are Geranium macrorhizum of which is known only one but very large stand, as well as Panicum riparium, the oldest herbarium specimens of which date back to the 1960ies. Panicum miliaceum subsp. Agricola is shown to have occurred in the 19th Century while new distributional data are missing. Instead, new records of the closely related subsp. ruderale can be provided proving the taxon actually being present in the flora region. Among the native taxa new to South Tyrol is the hybrid Elymus hispidus x repens, whereas the indigeneity of Carduus defloratus subsp. glaucus is unclear though possible. Of the non-native species Alcaea rosea and Catapodium rigidum, both reported from historical times, new distributional data are given. A new record of Cerastium dubium helped to overcome reservations regarding the actual occurrence of the species in South Tyrol as expressed in the catalogue. Apart from new records regarding the flora of South Tyrol, the present paper provides, as a result of herbarium revisions, first records for other Italian regions: Panicum riparium is new to the province of Trento and Eragrostis franckii new to the Campania region.