Boerhavia L., Sp. Pl. 1: 3. 1753 sec. Bittrich & Kühn (1993)



Boerhavia with c. 40 species is distributed in the warm temperate and tropical regions worldwide (Spellenberg 2003) and has been recognized as a natural group by Douglas and Manos (2007). Several authors (Fay 1980; Spellenberg 2001, 2003) have highlighted that at the species level this is a taxonomically difficult group due to morphological variation. Especially among annuals of the Sonoran desert and the pantropical B. diffusa Vahl and B. coccinea Mill. complex (Spellenberg 2001, 2003), apparently factors such as wide dispersal, hybridization, and autogamy have contributed to that variation (Fay 1980; Spellenberg 2001, 2003). The genus is in need of a critical revision.