Cardamine occulta Hornem. – a new concealed alien plant in the flora of Croatia

In the last decade of the 20th and in the early 21st century a new plant from East Asia, Cardamine occulta, was recorded in many European countries, and evaluated as a potential invasive species. Prior to our research, it had not been observed in Croatia or the neighbouring countries. During 2017, the first plants of C. occulta were discovered in plant nurseries in Zemunik Donji (near the city of Zadar), and in the city of Split. Since then, both sites have been monitored continuously, and the populations in both nurseries are still present and getting denser every year. In this work we aim to present a short history of the discovery, list newly-detected sites and establish some features (taxonomical peculiarities, plant description, distribution, growth and invasive preferences) of the species C. occulta to make its identification easier. Because of its invasive potential and morphological similarity with two other taxa distributed in Croatia, C. hirsuta and C. flexuosa, the determination key for all three taxa, as well as photos of C. occulta have been prepared. This will probably increase the chance of early detection of this species outside of cultivation.