Cerasus fruticosa Pall. (Rosaceae) in the region of Kujavia and South Pomerania (N Poland)

Cerasus fruticosa is a rare and endangered plant species in Poland. In northern part of the country it occurs on scattered localities of relic, early Holocene (preboreal) character. Most of the species stands known from the end of 19th century have disappeared in the last decades. All data, revised in the field 40 years ago, were checked in 2000-2002. The species survived on 6 localities of 14 ones, confirmed in sixteenth. The hybridization between C. fruticosa and C. vulgaris is one of the main reasons of extinction of the first species. The floristic composition of plant communities with C. fruticosa was examined and compared with relevant literature. The regression of photophilous and thermophilous plant species, characteristic for associations with C. fruticosa and moderate invasion of synanthropic ones were observed.