Nieuw-Zeelandse veldkers ‒ Cardamine corymbosa Hook.f. (Brassicaceae). Verstekeling krijgt vaste grond onder de voeten

Cardamine corymbosa has its natural range New Zealand. In the last quarter of the last century, however, this species has been accidentally introduced into Western Europe via the transport of potted plants. The introduction started in Scotland in 1975 and a few years later the species was found all over Great Britain. In Belgium and the Nether­lands the species appeared as a weed in ornamental horticulture around 2000; it was reported for the first time from a garden in the Province of Friesland. In Germany the species appeared for the first time in a nursery in Oldenburg, Lower Saxony, in 2005. While the first European sites were gardens, parks, and in particular cemeteries, in the Netherlands the species colonised urban areas as well and it is now established in almost all major cities. In the most recent 2020 Checklist of the flora of the Netherlands, C. corymbosa has even already been given the status ʻnaturalizedʼ. The small size of the plants, the few-flowered inflorescences, and the pollination mechanism of Cardamine corymbosa are remarkable features. In 2021 and 2022, the authors monitored a new population of this species in the old inner city of Deventer. This population consists of around 80 scattered rosettes which are growing between the bricks on the side of a street. After the first bloom in March, with open flowers with relatively large white petals, later bloom with inconspicuous cleistogamous flowers follow throughout the year. The long slender green siliques are striking and present until very late in the year. While the literature reports the colour of the plants as being green with a gradient to purple-brown, the Deventer plants are entirely bright green. The species' strength to survive is also remarkable. Despite frequent and intensive weed control of the Deventer site by using steam or mechanically brushing, the plants survive and hardly seem to suffer. The species can be considered as one of the permanent residents in at least the urban areas of ​​the Netherlands.