Abstract
Hesperis sylvestris is a cruciferous plant up to 2 m tall, with pale purple flowers, growing mainly in clearings in thermophilous forests. In 2019-2020 a spatially limited but richly flowering population, numbering about 280 plants, was found in the Bohemian Karst area near Radotín at the south-western outskirts of Prague (WGS 84: 49.9890N, 14.3446E).
This species was reported to occur in this area repeatedly between 1881 and 1915 but not later, until now. The locality lies at the north-western border of the geographic range of the species.
Hesperis sylvetris is rather common in southern Moravia (south-eastern part of the Czech Republic) but very rare in the western part of the country (Bohemia). In addition to the herein described locality, it occurs at two or three sites in the surroundings of the town of Nymburk east of Prague.
The article includes (a) a summary of the species' records extracted from herbaria and literature, starting from 1786 when Tadeáš Haenke found it on Chotuc Hill near the village of Křinec, (b) a detailed description of the locality near Radotín (including the list of plant species recorded at the 0.1 ha locality in June 2020), and (c) speculations concerning a possible relict origin of the species occurrence in this area, where it may have survived in the former coppiced oak forests for long and now re- -emerged in a forest clearing after an artificially planted mixed stand of Norway spruce and European larch. Finally (d), we suggest proposals for the protection of the population of H. sylvestris at the Radotín site: light stands or forest cleanings must be preserved as a mosaic; probably the best solution would be a re-establishment of coppicing.