A. Natural:
Argemone arizonica G.B. Ownbey is one of approximately 24 species in the genus, known from the southwestern United States, northern Mexico, with one species endemic to Hawaii and other weedy species naturalized elsewhere (Schwarzbach and Kadereit 1999). Argemone has been shown to be a sister group of Arctomecon, a genus comprising of three species endemic to the Mohave Desert (Schwarzbach and Kadereit 1999).
It is one of 13 species related to the two subspecies of A. corymbosa, however relationships within this clade are largely unresolved (Schwarzbach and Kadereit 1999). Of the 13 species, A. arizonica is related to A. munita and A. pleicantha. A. arizonica is reported to have very pale lemon-yellow latex in fresh cuts, while A. munita and A. pleiacantha have bright yellow sap (Ownbey 1958, Mason 1959, Kearney and Peebles 1960, McDougall 1973). One specimen (L. Mazzu s.n.) collected in June 1992 was noted to have clear sap from cut stems. The 1998 survey confirmed this feature of having clear sap after numerous stems, leaves, flower buds, and immature fruits were cut. However, latex color may change or not be as evident, especially during early or late growth of the plant (G. Ownbey, pers. comm. 1998).
Argemone subintegrifolia is considered the basal most taxon within the genus (Schwarzbach and Kadereit 1999). Because of its distribution in Baja California, it is postulated that an origin of the genus to be in this region. From here, it spread to two smaller areas in North America, to the Caribbean, to South America and Hawaii, and to the southern regions of the U.S. and northern Mexico. Argemone is from the Greek word for ocular cataract, supposedly remedied by sap of other plants with this name, and arizonica means of or from Arizona.
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