This globally rare annual occurs on dry, strongly acid soils on foothills and plains around the central and southern Appalachians, but it has often been hard to identify (Pennell 1935; W; B. Sorrie, pers. comm.). It may be threatened or endangered throughout its range, with no currently documented populations of high quality (NS). The species remains virtually unknown west of the Appalachians in Ky. and Tenn. (K, W). A. decemloba is close to A. obtusifolia Raf., a species largely found on the southeastern Coastal Plain that has been sometimes combined or confused, and thus reported from Ky. Recent molecular evidence has confirmed distinction from obtusifolia, but supports closer relationship with two other species of the Coastal Plain: the more southern A. tenella Pennell and especially the more northern A. acuta Pennell (Pettengill & Neel 2008). There has also been confusion with gattingeri, to which colls. from CALL are here reassigned (Woods 1983; M). Compared to gattingeri and especially tenuifolia, decemloba tends to have paler "dull green" color when dried (versus purplish to blackish), smoother and more angled stems, shorter leaves that do not curl when dried (mostly 1.5-2.5 cm versus 2-3 cm), more racemose inflorescences (with flowers mostly in groups of 5-20 versus 1-4), and emarginate petals (versus entire).