Cardamine occulta - a new mysterious weedy Cardamine species in the Czech Republic

This paper summarises data on altogether 25 localities of Cardamine occulta, an Eastern Asian alien, recognized for the first time in the Czech Republic in 2016. After a targeted search in herbaria, the date of the first occurrence of this species on the Czech territory had to be shifted to 2006. However, the first finds come from garden shops where C. occulta grew as a weed in pots with ornamental plants and the first escape outside the pots dates back to 2015. Recently the species has been documented as a weed in a broad range of habitats, including various places in garden shops (i. e. also in the surroundings of the pots and in flower beds), botanical gardens, flower beds and containers with ornamental plants in towns and at cemeteries, forest nurseries and along forest tracks, and on exposed fishpond bottoms. It quickly spreads at lower and middle altitudes and is expected to become naturalised in the Czech Republic in the near future, possibly with the status of invasive neophyte.