EN
This article reports the first record of a Mediterranean species Anthoxanthum aristatum Boiss. in corn-growing on Olsztyn Lake District. It grows on five stands only, near Naterki village, in the central part of the region. On most localities Anthoxanthum aristatum attains big cover and decidedly dominate over the other species. Anthoxanthum aristatum occurs in seldom Arnoserido-Scleranthetum [(Chouard 1925) Tx. 1937] association. This species hasn't been observed in the association on Olsztyn Lake District so far. A mass occurrence of Anthoxanthum aristatum has a degenerating effect on the Arnoserido-Scleranthetum association. This is very expansive species and it is possible to find the new field stands of Anthoxanthum aristatum on Olsztyn Lake District in the foreseeable future. It causes necessity of further studies on the expansion and distribution of this species in North-Eastern Poland.