This seventeenth part of floristic contributions includes records on alien species found in the Czech Republic for the first time (Cochlearia danica, Phleum exaratum and probably also Astragalus sulcatus and Scoparia dulcis) and taxa newly escaped from cultivation (Allium caeruleum, Asparagus verticillatus, Dichondra argentea, Gaura lindheimeri, Prunus tomentosa, Yucca flaccida).
Furthermore, critically endangered species (according to the Red List of Vascular Plants of the Czech Republic) are reported from new localities (e.g. Agropyron pectinatum, Botrychium multifidum, Carex depressa subsp. transsilvanica, Cirsium brachycephalum, Dactylorhiza fuchsii subsp. sooana, Epipactis pontica, Glaucium corniculatum, Orchis morio, Potamogeton gramineus, P. ×angustifolius, Pseudognaphalium luteoalbum, Sagina apetala, Samolus valerandi, Taraxacum disseminatum and Vulpia bromoides).
Finally, less rare and threatened species are reported from phytogeographical districts where they had not been recorded yet (Chenopodium botrys, Corispermum leptopterum, Epipactis atrorubens, Geranium molle, Pulmonaria angustifolia, Scrophularia umbrosa and Vulpia myuros).
