Polish Botanical Journal 48(1): 47–49, 2003 CYPERUS STRIGOSUS (CYPERACEAE), A NATURALIZED SPECIES NEW TO BULGARIA ROSSEN TZONEV, JERZY ZIELIN ´ SKI & KIT TAN Abstract: Cyperus strigosus L., an American species, is recorded from two localities in the Danube valley in northern Bulgaria. In Europe it had previously been recorded only from Italy. Key words: Cyperus strigosus, anthropophyte, Danube valley, Bulgaria, Europe Rossen Tzonev, Sofia University, Department of Botany, 8, D. Tsankov, Sofia 1521, Bulgaria Jerzy Zielin ´ski, Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, PL-62-035 Kórnik, Poland; e-mail: jeziel@rose.man.poznan.pl, jeziel@poczta.onet.pl Kit Tan, Botanical Institute, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark; e-mail: kitt@bot.ku.dk During a fieldwork in the Danube valley in the years 2000 and 2001, one of us (R.T.) found in two localities an interesting Cyperus which had not previously been recorded from Bulgaria (Fig. 1). We identified it as C. strigosus L., an American species, known in Europe only as a naturalized taxon in Italy (DeFilipps 1980). Bulgarian plants matched the descriptions of the species both in standard American floras (Gleason 1952; Cron- quist 1969; Kolstad 1986) and Flora Europaea (DeFilipps 1980); they have also been compared with herbarium specimens of native origin. Cypersus strigosus is widespread in North America (Canada and the United States) and ex- tends to tropical South America. The first do- cumentation of the species in Europe was in 1915, from Piedmont in north Italy (Mattirolo 1915). Since then it has spread in the northwestern part of the country from the province of Lomellina in the east to the province of Turin in the west, dis- tributed mainly in the Po valley (Pignatti 1997). Pistarino et al. (1999) list the species from the provinces of Novara, Vercelli, Alessandria and Pavia. As in its natural habitat it was found in wet places – moist fields, swamps, on the banks of large streams, in ditches etc., from sea level to 300 m (Pignatti 1997). In Bulgaria Cyperus strigosus was found on the right bank of the Danube river, in the area of Hi- sarlik, 4 km west of Belene and near the village of Novgrad, ca 45 km east of the first-named locality (Fig. 1). The population in Hisarlik, discovered in autumn 2000, consisted of ca 50 individuals scat- tered on wet alluvial sand, occupying an area of 1000–1500 m 2 . Other plants growing nearby were Cyperus glomeratus L., C. fuscus L., Plantago al- tissima L., Astragalus contortuplicatus L., Persi- caria maculata (Rafin.) A. Löve & D. Löve, Cryp- sis alopecuroides (Pill. & Mitt.) Schrad., Bidens 44° 42° 43° 44° 42° 43° 24° 26° 28° 24° 26° 28° Fig. 1. Distribution map of Cyperus strigosus L. in Bulgaria.