During the vegetation seasons 2008 and 2009 the floristic composition of the grasslands of Opeka Arboretum was surveyed. In total, 276 plant taxa were found, and 223 taxa were recorded for the first time for the investigated area. The taxa were classified into 66 families, the Poaceae (10.51%), Asteraceae (6.52%) and Lamiaceae (6.16%) families appearing among them with a relatively high number of taxa. In the Arboretum Opeka,12 red-listed native herbaceous plant taxa were found. There were also 36 species protected and 9 species strictly protected by law. Non-indigenous plants made up 14.13% of the flora of the investigated area: 6 archaeophytes, 6 neophytes, 28 cultivated species and 8 of them were invasive alien species. Floristic composition of native herbaceous vegetation in Opeka Arboretum should be maintained by regular mowing of grasslands.Tijekom vegetacijskih sezona 2008. i 2009. istraživan je floristički sastav travnjaka Arboretuma Opeka. Utvrđeno je 276 biljnih svojti, a 223 svojte su zabilježene prvi put za istraživano područje. Svojte su svrstane u 66 porodica, a među njima su s relativno visokim brojem svojti porodice Poaceae (10,51%), Asteraceae (6,52%) i Lamiaceae (6,16%). U Arboretumu Opeka je zabilježeno 12 svojti autohtonih zeljastih biljaka s Crvenog popisa, 36 vrsta zaštićenih i 9 vrsta strogo zaštićenih vrsta. Alohtone biljke čine 14,13% flore istraživanog područja: 6 arheofita, 6 neofita, 28 kultiviranih vrsta i 8 invazivnih stranih vrsta. Floristički sastav prirodne zeljaste vegetacije u Arboretumu Opeka trebao bi biti održavan redovitom košnjom travnjaka
