The hybrid Centaurium erythraea × pulchellum (Gentianaceae), newly recorded in the Netherlands and Belgium

In the summer of 2023, and again in 2024, a large population of an unidentified Centaurium was discovered at a recently excavated site along the River Meuse near Grevenbicht (Koeweide / Trierveld), the Netherlands. In 2024, morphologically identical plants were also found on the Belgian side of the river in Stokkem (Kerkeweerd), and in 2025 between Maasband and Meers, again on Dutch territory. The plants were morphologically highly uniform, fully fertile, and bore a striking resemblance to C. tenuiflorum, a species predominantly native to the Mediterranean region. However, several morphological traits also appeared intermediate between those of the native species C. erythraea and C. pulchellum. To determine the plants’ identity, genetic analyses were conducted and their genome size was measured using flow cytometry. The results demonstrated that, despite their apparent resemblance and fertility, the plants do not belong to C. tenuiflorum, but to the hybrid between C. erythraea and C. pulchellum. This taxon has previously only been recorded in the British Isles, France, and Germany, and thus the recent finds represents a new record for both the Netherlands and Belgium.