Bidens vulgatus Greene, Pittonia, 4 (21): 72. 1899. [Fig. 2]

( Asteraceae)

Naturalized neophyte new to the flora of Lombardia and Emilia-Romagna (Conti et al., 2005; Celesti-Grapow et al., 2009a; Banfi & Galasso, 2010).

ITALY. Lombardia. Prov. Cremona: Casalmaggiore, river Po, damp track in woodland, locally frequent, 14.09.2014, F. Verloove 11090 (BR, MSNM); Prov. Pavia: Gambolò, Cascina Portalupa (UTM ED 50: 32 T 495784.5013034), margine di sentiero in querco-carpineto, con Erigeron canadensis, Prunella vulgaris, Glechoma hederacea, 73 m, 17.10.2014, N. Ardenghi, P. Cauzzi & S. Pedrini (MSNM); Prov. Pavia: Stradella, San Zeno, sponda destra del torrente Versa all’incirca all’altezza della rotonda tra viale Resistenza e la SP 201 (UTM ED 50: 32 T 524108.4989963), vigneto, 86 m, 18.10.2014, N. Ardenghi (MSNM); Prov. Milano: Milano, stazione FFSS di Milano-Rogoredo (UTM ED 50: 32 T 518642.5031188), aiuola, 109 m, 28.11.2014, N. Ardenghi (MSNM) .

This is a widespread species in North America (Strother & Weedon, 2006). Like the preceding, it is poorly known and overlooked in Europe, although known since many decades (e.g. Schumacher, 1941; Debray, 1963). Up to present it was known in Italy only from Friuli-Venezia Giulia (Celesti-Grapow et al., 2009a). Bidens vulgatus is much reminiscent of B. frondosus L. but often more robust with larger flower heads and with a higher number of calyculi (10-16 vs. usually 8).

In addition to the localities cited above, it was also detected along river Po in Boretto (Emilia-Romagna). It may have been widely overlooked elsewhere.