In this paper, we report our floristic observations collected from gravel pits in the Sajó–Hernád Plain (Borsod-Abaúj-Zemplén county, Northeast Hungary). We present a total of 101 occurrence data from 13 pits, belonging to 45 vascular plant species and one hybrid. Most of the observations come from abandoned mines, but we also describe occurrences from actively mined areas. Ten of the presented species are new to the flora of the micro-region (Cyperus flavescens, Dysphania botrys, Helminthotheca echioides, Hippophae rhamnoides, Panicum dichotomiflorum, Ranunculus circinatus, Solanum lycopersicum, Spergularia rubra, Thymelaea passerina, Zannichellia palustris). Some of the species listed in the enumeration are taxa for which data are scarce even at the national level (e.g., Bolboschoenus laticarpus, B. planiculmis, Utricularia ×neglecta). We report some recent occurrences of invasive alien species (Erechtites hieraciifolia, Symphyotrichum ciliatum, S. novi-belgii), we provide data on common or sporadic aquatic plant species for which available data are scarce (Ceratophyllum demersum, Myriophyllum spicatum, Nuphar lutea, Potamogeton spp.), and we describe some new localities of species for which previous data – concerning the micro-region – came exclusively from gravel pits (e.g., Carex secalina, Cyperus glomeratus, Gnaphalium luteoalbum, Najas minor, Typha laxmannii). We discuss our results in the concluding section of the paper, taking into account previous floristic data as well.

Data on the distribution of the Pannonian endemic black hawthorn (Crataegus nigra Waldst. et Kit.) have been partly incorrect or uncertain. Older publications contain several confusions involving this species, the morphologically similar Crataegus pentagyna, and Crataegus ×degenii (C. nigra × C. monogyna). In this study, we review and evaluate records reported in the relevant literature as well as herbarium specimens. Current occurrences and population sizes were investigated through field surveys. We delineate the currently known distribution range of the species, which is restricted to the floodplain of the Danube between Budapest and the Iron Gate Gorge (Vaskapu), as well as to the vicinity of the mouths of the two major tributaries of the Danube, the Drava and the Sava. At present, the species is rare north of Gemenc and south of the mouth of the Tisza, and is probably extinct in the Belgrade region. Large populations occur in the Gemenc area (Hungary), the Kopački Rit–Apatin region (Croatia/Serbia), and the Kovilj–Gardinovci area (Serbia). The species is rapidly declining north of Gemenc owing to the desiccation of its habitats, hybridization with Crataegus monogyna, and the wide­spread invasion of alien plant species. Its conservation status in this region should be considered Criti­cally Endangered, whereas elsewhere it is more appropriately classified as Endangered.