This annual is known from scattered, somewhat disjunct localities in east-central states from Ark. and Mo. to Pa. and Va., especially in the Ohio Valley (K, FNA 12; G. Levin, pers. comm.). It is probably the same species as A. urticifolia Raf. (Rafinesque 1833, 1836), but no type has been located for that name: "In West Kentucky and Tennessee, discovered in 1818". The first known coll. from Ky. was made by C. Deam in WARR (IND) in the 1920s, and the next appears to have been in the 1970s. The species is probably more widespread than records indicate, but generally restricted to disturbed ground in damp fertile woodland, especially on levees near larger streams and rivers (in or near habitat of Laportea). It has also been found along smaller streams and low slopes on calcareous uplands, especially where deer browsing is intense. The species may even be increasing in recent decades, and spreading into uplands, due to increased deer populations (and sometimes associated with Achyranthes japonica). A. deamii is easily confused with typical rhomboidea, and occasional intermediates have been suggested, but hybrids are not confirmed. The species is best diagnosed by its fruits, which have two seeds ca. 2-3 mm long (versus three seeds ca. 1-2 mm long). Vegetative differences are less clear cut (F, Y; Levin 1999b, Becus 2003): leaf blades are usually bright green (versus often reddish/coppery); mid-cauline ones usually have broader shape (L/W ca. 1.3-1.8 versus 1.8-2.6), with bases often truncate (versus just cuneate).